Ant Hill or Plumbing System?<\/h1>\r\n<\/div>\r\nWhat do you think the picture in Figure 14.2.1 shows? Is it a maze of underground passageways in an ant hill? A network of interconnected pipes in a complex plumbing system? The picture actually shows something that, like ant tunnels and plumbing pipes, functions as a transportation system. It shows a network of blood vessels, which are part of the cardiovascular system.\r\n\r\nWhat is the Cardiovascular System?<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5927\"]cardiovascular system[\/pb_glossary]<\/strong>, also called the circulatory system, is the organ system that transports materials to and from all the cells of the body. The materials carried by the cardiovascular system include oxygen from the [pb_glossary id=\"2990\"]lungs[\/pb_glossary], nutrients from the [pb_glossary id=\"5969\"]digestive system[\/pb_glossary], [pb_glossary id=\"5661\"]hormones[\/pb_glossary] from glands of the [pb_glossary id=\"5985\"]endocrine system[\/pb_glossary], and waste materials from cells throughout the body. Transport of these and many other materials is necessary to maintain [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary] of the body. The main components of the cardiovascular system are the heart, blood vessels, and blood. Each of these components is shown in Figure 14.2.2 and introduced below.\r\n\r\n[caption id=\"attachment_4383\" align=\"aligncenter\" width=\"413\"]![\"14.2.2](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Circulatory_System_no_tags.svg_-2.png\")
Figure 14.2.2 This simplified drawing of the cardiovascular system shows its main structures. The heart is shown in the chest in red. Blood vessels called arteries are also shown in red, and blood vessels called veins are shown in blue.<\/em>[\/caption]\r\n\r\n\r\nHeart<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"2987\"]heart[\/pb_glossary]<\/strong> is a muscular organ in the chest. It consists mainly of [pb_glossary id=\"5925\"]cardiac muscle[\/pb_glossary] tissue, and it pumps blood through blood vessels by repeated, rhythmic contractions. As shown in Figure 14.2.3, the heart has four inner chambers: a right atrium and ventricle, and a left atrium and ventricle. On each side of the heart, blood is pumped from the atrium to the ventricle below it, and from the ventricle out of the heart. The heart also contains several valves that allow blood to flow only in the proper direction through the heart.\r\n\r\n[caption id=\"attachment_4384\" align=\"aligncenter\" width=\"394\"]![\"14.2.3](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Blausen_0462_HeartAnatomy-2.png\")
Figure 14.2.3 The right side of the heart includes the right atrium and right ventricle. The left side includes the left atrium and left ventricle.<\/em>[\/caption]\r\n\r\n \r\n\r\nAs you may have noticed, the Figure 14.2.3 diagram labels the right side of the heart on the left side of the diagram, and vice versa.\u00a0 This is because it is assumed that in this diagram, the heart appears\u00a0 as if the patient was facing us - the patient's left side is on our right side!\r\n\r\nUnlike skeletal muscle, cardiac muscle routinely contracts without stimulation by the\u00a0nervous system. Specialized cardiac muscle\u00a0cells\u00a0send out electrical impulses that stimulate the contractions. As a result, the atria and ventricles normally contract with just the right timing to keep blood pumping efficiently through the heart.\r\n\r\nBlood Vessels<\/h1>\r\n<\/div>\r\nThe [pb_glossary id=\"5835\"]blood vessels[\/pb_glossary] of the cardiovascular system are like a network of interconnected, one-way roads that range from superhighways to back alleys. Like a network of roads, the blood vessels are tasked with allowing the transport of materials from one place to another. There are three major types of blood vessels: arteries, veins, and capillaries. They are illustrated in Figure 14.2.4 and described below.\r\n\r\n[caption id=\"attachment_4388\" align=\"aligncenter\" width=\"500\"]![\"14.2.4](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Types-of-blood-vessels-by-CK-12-Foundation-2.png\")
Figure 14.2.4 This diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system.<\/em>[\/caption]\r\n\r\n \t- [pb_glossary id=\"4385\"]Arteries[\/pb_glossary]<\/strong>\u00a0are blood vessels that carry blood away from the heart (except for the arteries that actually supply blood to the heart muscle). Most arteries carry oxygen-rich blood, and one of their main functions is distributing oxygen to tissues throughout the body. The smallest arteries are called arterioles.<\/li>\r\n \t
- [pb_glossary id=\"4386\"]Veins[\/pb_glossary]<\/strong>\u00a0are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood. The smallest veins are called venules.<\/li>\r\n \t
- [pb_glossary id=\"5923\"]Capillaries[\/pb_glossary]<\/strong>\u00a0are the smallest blood vessels, and they connect arterioles and venules. As they pass through tissues, they exchange substances (including oxygen) with\u00a0cells.<\/li>\r\n<\/ul>\r\n\r\n
Two Circulations<\/h1>\r\n<\/div>\r\nCells throughout the body need a constant supply of oxygen. They get oxygen from capillaries in the systemic circulation. The systemic circulation is just one of two interconnected circulations that make up the human cardiovascular system. The other circulation is the pulmonary system, which is where blood picks up oxygen to carry to cells. It takes blood about 20 seconds to make one complete transit through both circulations (see Figure 14.2.5).\r\n\r\n[caption id=\"attachment_4389\" align=\"aligncenter\" width=\"927\"]![\"14.2.5](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/2101_Blood_Flow_Through_the_Heart-2.jpg\")
Figure 14.2.5 There are two main circuits through which blood flows in the cardiovascular system. In the pulmonary circuit, blood moves from the right side of the heart to the lungs and then back to the left side of the heart. In the systemic circuit, blood moves from the left side of the heart to the body tissues and then back to the right side of the heart.<\/em>[\/caption]\r\nPulmonary Circuit<\/h2>\r\nThe\u00a0[pb_glossary id=\"4387\"]pulmonary<\/strong>\u00a0<\/strong>circuit<\/strong>[\/pb_glossary] involves only the heart, the lungs, and the major blood vessels that connect them (illustrated in Figure 14.2.6). Blood moves through the pulmonary circuit from the heart, to the lungs, and then back to the heart again, becoming oxygenated in the process. Specifically, the right ventricle of the heart pumps deoxygenated blood into the right and left pulmonary arteries. These arteries carry the blood to the right and left lungs, respectively. Oxygenated blood then returns from the right and left lungs through the two right and two left pulmonary veins. All four pulmonary veins enter the left atrium of the heart.\r\n\r\n[caption id=\"attachment_4391\" align=\"aligncenter\" width=\"520\"]![\"14.2.6](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Illu_pulmonary_circuit-2.jpg\")
Figure 14.2.6 This diagram shows the heart, lungs, and major vessels that make up the pulmonary circulation. The coloured arrows indicate the direction of blood flow \u2014 red for oxygenated blood and blue for relatively deoxygenated blood.<\/em>[\/caption]\r\n\r\nWhat happens to the blood while it is in the lungs? It passes through increasingly smaller arteries, and finally through capillary networks surrounding the alveoli (see Figure 14.2.7). This is where gas exchange takes place. The deoxygenated blood in the capillaries picks up oxygen from the alveoli, and gives up carbon dioxide to the alveoli. As a result, the blood returning to the heart in the pulmonary veins is almost completely saturated with oxygen.\r\n\r\n[caption id=\"attachment_4392\" align=\"aligncenter\" width=\"812\"]![\"14.2.7](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Pulmonary_Blood_Circulation-2.png\")
Figure 14.2.7 This diagram illustrates clusters of alveoli in the lungs, where gas exchange takes place with blood in capillaries as it passes through the pulmonary circulation.<\/em>[\/caption]\r\nSystemic Circulation<\/h2>\r\nThe oxygenated blood that enters the left atrium of the heart in the pulmonary circulation then passes into the\u00a0[pb_glossary id=\"4393\"]systemic circuit[\/pb_glossary].<\/strong>\u00a0This is the part of the cardiovascular system that transports blood to and from all of the tissues of the body to provide oxygen and\u00a0nutrients, and to pick up wastes. It consists of the heart and blood vessels that supply the metabolic needs of all the cells in the body, including those of the heart and lungs.\r\n\r\nAs shown in Figure 14.2.8, in the systemic circulation, the left atrium pumps oxygenated blood to the left ventricle, which pumps the blood directly into the aorta, the body\u2019s largest artery. Major arteries branching off the aorta carry the blood to the head and upper extremities. The aorta continues down through the abdomen and carries blood to the abdomen and lower extremities. The blood then returns to the heart through the network of increasingly larger veins of the systemic circulation. All of the returning blood eventually collects in the superior vena cava (upper body) and inferior vena cava (lower body), which empty directly into the right atrium of the heart.\r\n\r\n[caption id=\"attachment_4394\" align=\"aligncenter\" width=\"566\"]![\"14.2.8](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/systemic_circuit.svg_-2.png\")
Figure 14.2.8 The systemic circulation includes the aorta (red), which carries oxygenated blood away from the heart to the rest of the body; and the inferior and superior venae cavae (blue), which return deoxygenated blood to the heart from the body. The coloured arrows in the diagram indicate the direction of blood flow \u2014 red for oxygenated and blue for deoxygenated.<\/em>[\/caption]\r\nBlood<\/h2>\r\n[caption id=\"attachment_4396\" align=\"alignright\" width=\"500\"]![\"14.2.9](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Red_White_Blood_cells-2.jpg\")
Figure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em>[\/caption]\r\n\r\n[pb_glossary id=\"2702\"]Blood[\/pb_glossary]<\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0[pb_glossary id=\"4330\"]pH[\/pb_glossary], among other functions.\r\n\r\nThe fluid part of blood is called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary]<\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.\r\n\r\n \t- [pb_glossary id=\"4398\"]Erythrocytes[\/pb_glossary] <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0[pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary]<\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\r\n \t
- [pb_glossary id=\"5623\"]Leukocytes[\/pb_glossary] <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\r\n \t
- [pb_glossary id=\"4399\"]Thrombocytes[\/pb_glossary]<\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\r\n<\/ul>\r\n\r\n
\r\n14.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5927\"]cardiovascular system[\/pb_glossary] is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the [pb_glossary id=\"2987\"]heart[\/pb_glossary], [pb_glossary id=\"5835\"]blood vessels[\/pb_glossary], and [pb_glossary id=\"2702\"]blood[\/pb_glossary].<\/li>\r\n \t
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\r\n \t
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\r\n \t
- The cardiovascular system has two interconnected circulations. The [pb_glossary id=\"4387\"]pulmonary circuit[\/pb_glossary] carries blood between the heart and lungs, where blood is oxygenated. The [pb_glossary id=\"4393\"]systemic circuit[\/pb_glossary] carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\r\n \t
- Blood is a [pb_glossary id=\"4402\"]fluid connective tissue[\/pb_glossary] that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary] \u2014 which contains many dissolved substances, and cells, including [pb_glossary id=\"4398\"]erythrocytes[\/pb_glossary], [pb_glossary id=\"5623\"]leukocytes[\/pb_glossary] and [pb_glossary id=\"4399\"]thrombocytes[\/pb_glossary].<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n14.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the heart and how it functions.<\/li>\r\n \t
- Compare and contrast the pulmonary and systemic circulations.<\/li>\r\n \t
- [h5p id=\"612\"]<\/li>\r\n \t
- What is blood? What are its chief constituents?<\/li>\r\n \t
- Name three different types of substances transported by the cardiovascular system.<\/li>\r\n \t
- Explain why the heart and lungs need blood from the systemic circulation.<\/li>\r\n \t
- Do blood vessels carrying deoxygenated blood from the body back to the heart get increasingly larger or smaller?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n14.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=emb_logo\r\nHow the heart actually pumps blood - Edmond Hui, TED-Ed, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=emb_logo\r\n
Circulatory & Respiratory Systems - CrashCourse Biology #27, CrashCourse, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU\r\n
The Heart and Circulatory System - How They Work, Mayo Clinic, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 14.2.1<\/strong>\r\n\r\nBrain vascular formation<\/a> [photo] by Liulin Du\/ Chen (The National Cancer Institute at Frederick) on PLOS Biology<\/a> is used under a CC BY 4.0<\/a> license.\r\n\r\nFigure 14.2.2<\/strong>\r\n\r\nCirculatory_System_no_tags.svg<\/a> by Mariana Ruiz Villarreal [LadyofHats]<\/a> on Wikimedia Commons is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.3<\/strong>\r\n\r\nBlausen_0462_HeartAnatomy<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0)\r\n\r\nFigure 14.2.4<\/strong>\r\n\r\nStructure and functions of the different types of blood vessels<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n![\"\"](\"https:\/\/www.ck12info.org\/wp-content\/uploads\/2016\/05\/logo_ck12.png\")
\u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span>![\"CK-12](\"https:\/\/www.ck12info.org\/wp-content\/uploads\/2016\/05\/icon_licence.png\" "\\"CK-12")
<\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\r\nFigure 14.2.5<\/strong>\r\n\r\n2101_Blood_Flow_Through_the_Heart<\/a>\u00a0by OpenStax College<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.6<\/strong>\r\n\r\nIllu_pulmonary_circuit<\/a> by Arcadian<\/a> from National Cancer Institute\/ SEER Training<\/a> on Wikimedia Commons is in the the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.7<\/strong>\r\n\r\nPulmonary_Blood_Circulation<\/a> by Artwork by Holly Fischer from Open Michigan (Respiratory Tact Slide 20)<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.8<\/strong>\r\n\r\nsystemic_circuit.svg<\/a> by Surachit<\/a> on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/) license. (Derivative work based on SEER Training by NCI\/ U.S. Government<\/a>).\r\n\r\nFigure 14.2.9<\/strong>\r\n\r\nRed_White_Blood_cells<\/a> by Electron Microscopy Facility at The National Cancer Institute at Frederick (NCI-Frederick) on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\nReferences<\/h2>\r\n
Blausen.com Staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine<\/i>\u00a01<\/b>\u00a0(2).\u00a0DOI:10.15347\/wjm\/2014.010.\u00a0ISSN\u00a02002-4436<\/p>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 20.2 Cardiovascular circulation [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 7.3). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/20-1-structure-and-function-of-blood-vessels<\/p>\r\nBrainard, J\/ CK-12 Foundation. (2016). Figure 4 Diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system [digital image]. In CK-12 College Human Biology<\/em> (Section 16.2) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/16.2\/<\/p>\r\nCrashCourse. (2012, July 30). Circulatory & respiratory systems - CrashCourse Biology #27. YouTube. https:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=youtu.be<\/p>\r\n
Du, J. (2012, August). Brain vasculature formation [digital image]. PLoS Biology,<\/em> 10(8): ev10.i08. https:\/\/doi.org\/10.1371\/image.pbio.v10.i08 \u00a9 Chen.<\/p>\r\nMayo Clinic. (2013). The heart and circulatory system - How they work. YouTube. https:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU&t=1s<\/p>\r\n
TED-Ed. (2014, May 20). How the heart actually pumps blood - Edmond Hui. YouTube. https:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\n![\"14.2.1](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2019\/06\/Brain-vascular-formation-by-Chen-CC-BY-from-PLoS-Biology-Issue-10-8-Aug-2012-2.png\")
Figure 14.2.1 What are these strange tunnels?<\/em><\/figcaption><\/figure>\n\nAnt Hill or Plumbing System?<\/h1>\n<\/div>\n
What do you think the picture in Figure 14.2.1 shows? Is it a maze of underground passageways in an ant hill? A network of interconnected pipes in a complex plumbing system? The picture actually shows something that, like ant tunnels and plumbing pipes, functions as a transportation system. It shows a network of blood vessels, which are part of the cardiovascular system.<\/p>\n
\nWhat is the Cardiovascular System?<\/h1>\n<\/div>\n
The\u00a0cardiovascular system<\/a><\/strong>, also called the circulatory system, is the organ system that transports materials to and from all the cells of the body. The materials carried by the cardiovascular system include oxygen from the lungs<\/a>, nutrients from the digestive system<\/a>, hormones<\/a> from glands of the endocrine system<\/a>, and waste materials from cells throughout the body. Transport of these and many other materials is necessary to maintain homeostasis<\/a> of the body. The main components of the cardiovascular system are the heart, blood vessels, and blood. Each of these components is shown in Figure 14.2.2 and introduced below.<\/p>\nFigure 14.2.2 This simplified drawing of the cardiovascular system shows its main structures. The heart is shown in the chest in red. Blood vessels called arteries are also shown in red, and blood vessels called veins are shown in blue.<\/em><\/figcaption><\/figure>\n\nHeart<\/h1>\n<\/div>\n
The\u00a0heart<\/a><\/strong> is a muscular organ in the chest. It consists mainly of cardiac muscle<\/a> tissue, and it pumps blood through blood vessels by repeated, rhythmic contractions. As shown in Figure 14.2.3, the heart has four inner chambers: a right atrium and ventricle, and a left atrium and ventricle. On each side of the heart, blood is pumped from the atrium to the ventricle below it, and from the ventricle out of the heart. The heart also contains several valves that allow blood to flow only in the proper direction through the heart.<\/p>\nFigure 14.2.3 The right side of the heart includes the right atrium and right ventricle. The left side includes the left atrium and left ventricle.<\/em><\/figcaption><\/figure>\n <\/p>\n
As you may have noticed, the Figure 14.2.3 diagram labels the right side of the heart on the left side of the diagram, and vice versa.\u00a0 This is because it is assumed that in this diagram, the heart appears\u00a0 as if the patient was facing us – the patient’s left side is on our right side!<\/p>\n
Unlike skeletal muscle, cardiac muscle routinely contracts without stimulation by the\u00a0nervous system. Specialized cardiac muscle\u00a0cells\u00a0send out electrical impulses that stimulate the contractions. As a result, the atria and ventricles normally contract with just the right timing to keep blood pumping efficiently through the heart.<\/p>\n
\nBlood Vessels<\/h1>\n<\/div>\n
The blood vessels<\/a> of the cardiovascular system are like a network of interconnected, one-way roads that range from superhighways to back alleys. Like a network of roads, the blood vessels are tasked with allowing the transport of materials from one place to another. There are three major types of blood vessels: arteries, veins, and capillaries. They are illustrated in Figure 14.2.4 and described below.<\/p>\nFigure 14.2.4 This diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system.<\/em><\/figcaption><\/figure>\n\n- Arteries<\/a><\/strong>\u00a0are blood vessels that carry blood away from the heart (except for the arteries that actually supply blood to the heart muscle). Most arteries carry oxygen-rich blood, and one of their main functions is distributing oxygen to tissues throughout the body. The smallest arteries are called arterioles.<\/li>\n
- Veins<\/a><\/strong>\u00a0are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood. The smallest veins are called venules.<\/li>\n
- Capillaries<\/a><\/strong>\u00a0are the smallest blood vessels, and they connect arterioles and venules. As they pass through tissues, they exchange substances (including oxygen) with\u00a0cells.<\/li>\n<\/ul>\n\n
Two Circulations<\/h1>\n<\/div>\n
Cells throughout the body need a constant supply of oxygen. They get oxygen from capillaries in the systemic circulation. The systemic circulation is just one of two interconnected circulations that make up the human cardiovascular system. The other circulation is the pulmonary system, which is where blood picks up oxygen to carry to cells. It takes blood about 20 seconds to make one complete transit through both circulations (see Figure 14.2.5).<\/p>\nFigure 14.2.5 There are two main circuits through which blood flows in the cardiovascular system. In the pulmonary circuit, blood moves from the right side of the heart to the lungs and then back to the left side of the heart. In the systemic circuit, blood moves from the left side of the heart to the body tissues and then back to the right side of the heart.<\/em><\/figcaption><\/figure>\nPulmonary Circuit<\/h2>\n
The\u00a0pulmonary<\/strong>\u00a0<\/strong>circuit<\/strong><\/a> involves only the heart, the lungs, and the major blood vessels that connect them (illustrated in Figure 14.2.6). Blood moves through the pulmonary circuit from the heart, to the lungs, and then back to the heart again, becoming oxygenated in the process. Specifically, the right ventricle of the heart pumps deoxygenated blood into the right and left pulmonary arteries. These arteries carry the blood to the right and left lungs, respectively. Oxygenated blood then returns from the right and left lungs through the two right and two left pulmonary veins. All four pulmonary veins enter the left atrium of the heart.<\/p>\nFigure 14.2.6 This diagram shows the heart, lungs, and major vessels that make up the pulmonary circulation. The coloured arrows indicate the direction of blood flow \u2014 red for oxygenated blood and blue for relatively deoxygenated blood.<\/em><\/figcaption><\/figure>\nWhat happens to the blood while it is in the lungs? It passes through increasingly smaller arteries, and finally through capillary networks surrounding the alveoli (see Figure 14.2.7). This is where gas exchange takes place. The deoxygenated blood in the capillaries picks up oxygen from the alveoli, and gives up carbon dioxide to the alveoli. As a result, the blood returning to the heart in the pulmonary veins is almost completely saturated with oxygen.<\/p>\nFigure 14.2.7 This diagram illustrates clusters of alveoli in the lungs, where gas exchange takes place with blood in capillaries as it passes through the pulmonary circulation.<\/em><\/figcaption><\/figure>\nSystemic Circulation<\/h2>\n
The oxygenated blood that enters the left atrium of the heart in the pulmonary circulation then passes into the\u00a0systemic circuit<\/a>.<\/strong>\u00a0This is the part of the cardiovascular system that transports blood to and from all of the tissues of the body to provide oxygen and\u00a0nutrients, and to pick up wastes. It consists of the heart and blood vessels that supply the metabolic needs of all the cells in the body, including those of the heart and lungs.<\/p>\nAs shown in Figure 14.2.8, in the systemic circulation, the left atrium pumps oxygenated blood to the left ventricle, which pumps the blood directly into the aorta, the body\u2019s largest artery. Major arteries branching off the aorta carry the blood to the head and upper extremities. The aorta continues down through the abdomen and carries blood to the abdomen and lower extremities. The blood then returns to the heart through the network of increasingly larger veins of the systemic circulation. All of the returning blood eventually collects in the superior vena cava (upper body) and inferior vena cava (lower body), which empty directly into the right atrium of the heart.<\/p>\nFigure 14.2.8 The systemic circulation includes the aorta (red), which carries oxygenated blood away from the heart to the rest of the body; and the inferior and superior venae cavae (blue), which return deoxygenated blood to the heart from the body. The coloured arrows in the diagram indicate the direction of blood flow \u2014 red for oxygenated and blue for deoxygenated.<\/em><\/figcaption><\/figure>\nBlood<\/h2>\nFigure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em><\/figcaption><\/figure>\nBlood<\/a><\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0pH<\/a>, among other functions.<\/p>\nThe fluid part of blood is called\u00a0plasma<\/a><\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.<\/p>\n\n- Erythrocytes<\/a> <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0hemoglobin<\/a><\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\n
- Leukocytes<\/a> <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\n
- Thrombocytes<\/a><\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\n<\/ul>\n\n\n
\n14.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- The cardiovascular system<\/a> is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the heart<\/a>, blood vessels<\/a>, and blood<\/a>.<\/li>\n
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\n
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\n
- The cardiovascular system has two interconnected circulations. The pulmonary circuit<\/a> carries blood between the heart and lungs, where blood is oxygenated. The systemic circuit<\/a> carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\n
- Blood is a fluid connective tissue<\/a> that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0plasma<\/a> \u2014 which contains many dissolved substances, and cells, including erythrocytes<\/a>, leukocytes<\/a> and thrombocytes<\/a>.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n14.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the heart and how it functions.<\/li>\n
- Compare and contrast the pulmonary and systemic circulations.<\/li>\n
- \n\n
What is the Cardiovascular System?<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5927\"]cardiovascular system[\/pb_glossary]<\/strong>, also called the circulatory system, is the organ system that transports materials to and from all the cells of the body. The materials carried by the cardiovascular system include oxygen from the [pb_glossary id=\"2990\"]lungs[\/pb_glossary], nutrients from the [pb_glossary id=\"5969\"]digestive system[\/pb_glossary], [pb_glossary id=\"5661\"]hormones[\/pb_glossary] from glands of the [pb_glossary id=\"5985\"]endocrine system[\/pb_glossary], and waste materials from cells throughout the body. Transport of these and many other materials is necessary to maintain [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary] of the body. The main components of the cardiovascular system are the heart, blood vessels, and blood. Each of these components is shown in Figure 14.2.2 and introduced below.\r\n\r\n[caption id=\"attachment_4383\" align=\"aligncenter\" width=\"413\"] Figure 14.2.2 This simplified drawing of the cardiovascular system shows its main structures. The heart is shown in the chest in red. Blood vessels called arteries are also shown in red, and blood vessels called veins are shown in blue.<\/em>[\/caption]\r\n\r\n\r\nHeart<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"2987\"]heart[\/pb_glossary]<\/strong> is a muscular organ in the chest. It consists mainly of [pb_glossary id=\"5925\"]cardiac muscle[\/pb_glossary] tissue, and it pumps blood through blood vessels by repeated, rhythmic contractions. As shown in Figure 14.2.3, the heart has four inner chambers: a right atrium and ventricle, and a left atrium and ventricle. On each side of the heart, blood is pumped from the atrium to the ventricle below it, and from the ventricle out of the heart. The heart also contains several valves that allow blood to flow only in the proper direction through the heart.\r\n\r\n[caption id=\"attachment_4384\" align=\"aligncenter\" width=\"394\"] Figure 14.2.3 The right side of the heart includes the right atrium and right ventricle. The left side includes the left atrium and left ventricle.<\/em>[\/caption]\r\n\r\n \r\n\r\nAs you may have noticed, the Figure 14.2.3 diagram labels the right side of the heart on the left side of the diagram, and vice versa.\u00a0 This is because it is assumed that in this diagram, the heart appears\u00a0 as if the patient was facing us - the patient's left side is on our right side!\r\n\r\nUnlike skeletal muscle, cardiac muscle routinely contracts without stimulation by the\u00a0nervous system. Specialized cardiac muscle\u00a0cells\u00a0send out electrical impulses that stimulate the contractions. As a result, the atria and ventricles normally contract with just the right timing to keep blood pumping efficiently through the heart.\r\n\r\nBlood Vessels<\/h1>\r\n<\/div>\r\nThe [pb_glossary id=\"5835\"]blood vessels[\/pb_glossary] of the cardiovascular system are like a network of interconnected, one-way roads that range from superhighways to back alleys. Like a network of roads, the blood vessels are tasked with allowing the transport of materials from one place to another. There are three major types of blood vessels: arteries, veins, and capillaries. They are illustrated in Figure 14.2.4 and described below.\r\n\r\n[caption id=\"attachment_4388\" align=\"aligncenter\" width=\"500\"] Figure 14.2.4 This diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system.<\/em>[\/caption]\r\n\r\n \t- [pb_glossary id=\"4385\"]Arteries[\/pb_glossary]<\/strong>\u00a0are blood vessels that carry blood away from the heart (except for the arteries that actually supply blood to the heart muscle). Most arteries carry oxygen-rich blood, and one of their main functions is distributing oxygen to tissues throughout the body. The smallest arteries are called arterioles.<\/li>\r\n \t
- [pb_glossary id=\"4386\"]Veins[\/pb_glossary]<\/strong>\u00a0are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood. The smallest veins are called venules.<\/li>\r\n \t
- [pb_glossary id=\"5923\"]Capillaries[\/pb_glossary]<\/strong>\u00a0are the smallest blood vessels, and they connect arterioles and venules. As they pass through tissues, they exchange substances (including oxygen) with\u00a0cells.<\/li>\r\n<\/ul>\r\n\r\n
Two Circulations<\/h1>\r\n<\/div>\r\nCells throughout the body need a constant supply of oxygen. They get oxygen from capillaries in the systemic circulation. The systemic circulation is just one of two interconnected circulations that make up the human cardiovascular system. The other circulation is the pulmonary system, which is where blood picks up oxygen to carry to cells. It takes blood about 20 seconds to make one complete transit through both circulations (see Figure 14.2.5).\r\n\r\n[caption id=\"attachment_4389\" align=\"aligncenter\" width=\"927\"] Figure 14.2.5 There are two main circuits through which blood flows in the cardiovascular system. In the pulmonary circuit, blood moves from the right side of the heart to the lungs and then back to the left side of the heart. In the systemic circuit, blood moves from the left side of the heart to the body tissues and then back to the right side of the heart.<\/em>[\/caption]\r\nPulmonary Circuit<\/h2>\r\nThe\u00a0[pb_glossary id=\"4387\"]pulmonary<\/strong>\u00a0<\/strong>circuit<\/strong>[\/pb_glossary] involves only the heart, the lungs, and the major blood vessels that connect them (illustrated in Figure 14.2.6). Blood moves through the pulmonary circuit from the heart, to the lungs, and then back to the heart again, becoming oxygenated in the process. Specifically, the right ventricle of the heart pumps deoxygenated blood into the right and left pulmonary arteries. These arteries carry the blood to the right and left lungs, respectively. Oxygenated blood then returns from the right and left lungs through the two right and two left pulmonary veins. All four pulmonary veins enter the left atrium of the heart.\r\n\r\n[caption id=\"attachment_4391\" align=\"aligncenter\" width=\"520\"] Figure 14.2.6 This diagram shows the heart, lungs, and major vessels that make up the pulmonary circulation. The coloured arrows indicate the direction of blood flow \u2014 red for oxygenated blood and blue for relatively deoxygenated blood.<\/em>[\/caption]\r\n\r\nWhat happens to the blood while it is in the lungs? It passes through increasingly smaller arteries, and finally through capillary networks surrounding the alveoli (see Figure 14.2.7). This is where gas exchange takes place. The deoxygenated blood in the capillaries picks up oxygen from the alveoli, and gives up carbon dioxide to the alveoli. As a result, the blood returning to the heart in the pulmonary veins is almost completely saturated with oxygen.\r\n\r\n[caption id=\"attachment_4392\" align=\"aligncenter\" width=\"812\"] Figure 14.2.7 This diagram illustrates clusters of alveoli in the lungs, where gas exchange takes place with blood in capillaries as it passes through the pulmonary circulation.<\/em>[\/caption]\r\nSystemic Circulation<\/h2>\r\nThe oxygenated blood that enters the left atrium of the heart in the pulmonary circulation then passes into the\u00a0[pb_glossary id=\"4393\"]systemic circuit[\/pb_glossary].<\/strong>\u00a0This is the part of the cardiovascular system that transports blood to and from all of the tissues of the body to provide oxygen and\u00a0nutrients, and to pick up wastes. It consists of the heart and blood vessels that supply the metabolic needs of all the cells in the body, including those of the heart and lungs.\r\n\r\nAs shown in Figure 14.2.8, in the systemic circulation, the left atrium pumps oxygenated blood to the left ventricle, which pumps the blood directly into the aorta, the body\u2019s largest artery. Major arteries branching off the aorta carry the blood to the head and upper extremities. The aorta continues down through the abdomen and carries blood to the abdomen and lower extremities. The blood then returns to the heart through the network of increasingly larger veins of the systemic circulation. All of the returning blood eventually collects in the superior vena cava (upper body) and inferior vena cava (lower body), which empty directly into the right atrium of the heart.\r\n\r\n[caption id=\"attachment_4394\" align=\"aligncenter\" width=\"566\"] Figure 14.2.8 The systemic circulation includes the aorta (red), which carries oxygenated blood away from the heart to the rest of the body; and the inferior and superior venae cavae (blue), which return deoxygenated blood to the heart from the body. The coloured arrows in the diagram indicate the direction of blood flow \u2014 red for oxygenated and blue for deoxygenated.<\/em>[\/caption]\r\nBlood<\/h2>\r\n[caption id=\"attachment_4396\" align=\"alignright\" width=\"500\"] Figure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em>[\/caption]\r\n\r\n[pb_glossary id=\"2702\"]Blood[\/pb_glossary]<\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0[pb_glossary id=\"4330\"]pH[\/pb_glossary], among other functions.\r\n\r\nThe fluid part of blood is called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary]<\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.\r\n\r\n \t- [pb_glossary id=\"4398\"]Erythrocytes[\/pb_glossary] <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0[pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary]<\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\r\n \t
- [pb_glossary id=\"5623\"]Leukocytes[\/pb_glossary] <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\r\n \t
- [pb_glossary id=\"4399\"]Thrombocytes[\/pb_glossary]<\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\r\n<\/ul>\r\n\r\n
\r\n14.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5927\"]cardiovascular system[\/pb_glossary] is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the [pb_glossary id=\"2987\"]heart[\/pb_glossary], [pb_glossary id=\"5835\"]blood vessels[\/pb_glossary], and [pb_glossary id=\"2702\"]blood[\/pb_glossary].<\/li>\r\n \t
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\r\n \t
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\r\n \t
- The cardiovascular system has two interconnected circulations. The [pb_glossary id=\"4387\"]pulmonary circuit[\/pb_glossary] carries blood between the heart and lungs, where blood is oxygenated. The [pb_glossary id=\"4393\"]systemic circuit[\/pb_glossary] carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\r\n \t
- Blood is a [pb_glossary id=\"4402\"]fluid connective tissue[\/pb_glossary] that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary] \u2014 which contains many dissolved substances, and cells, including [pb_glossary id=\"4398\"]erythrocytes[\/pb_glossary], [pb_glossary id=\"5623\"]leukocytes[\/pb_glossary] and [pb_glossary id=\"4399\"]thrombocytes[\/pb_glossary].<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n14.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the heart and how it functions.<\/li>\r\n \t
- Compare and contrast the pulmonary and systemic circulations.<\/li>\r\n \t
- [h5p id=\"612\"]<\/li>\r\n \t
- What is blood? What are its chief constituents?<\/li>\r\n \t
- Name three different types of substances transported by the cardiovascular system.<\/li>\r\n \t
- Explain why the heart and lungs need blood from the systemic circulation.<\/li>\r\n \t
- Do blood vessels carrying deoxygenated blood from the body back to the heart get increasingly larger or smaller?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n14.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=emb_logo\r\nHow the heart actually pumps blood - Edmond Hui, TED-Ed, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=emb_logo\r\n
Circulatory & Respiratory Systems - CrashCourse Biology #27, CrashCourse, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU\r\n
The Heart and Circulatory System - How They Work, Mayo Clinic, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 14.2.1<\/strong>\r\n\r\nBrain vascular formation<\/a> [photo] by Liulin Du\/ Chen (The National Cancer Institute at Frederick) on PLOS Biology<\/a> is used under a CC BY 4.0<\/a> license.\r\n\r\nFigure 14.2.2<\/strong>\r\n\r\nCirculatory_System_no_tags.svg<\/a> by Mariana Ruiz Villarreal [LadyofHats]<\/a> on Wikimedia Commons is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.3<\/strong>\r\n\r\nBlausen_0462_HeartAnatomy<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0)\r\n\r\nFigure 14.2.4<\/strong>\r\n\r\nStructure and functions of the different types of blood vessels<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\r\nFigure 14.2.5<\/strong>\r\n\r\n2101_Blood_Flow_Through_the_Heart<\/a>\u00a0by OpenStax College<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.6<\/strong>\r\n\r\nIllu_pulmonary_circuit<\/a> by Arcadian<\/a> from National Cancer Institute\/ SEER Training<\/a> on Wikimedia Commons is in the the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.7<\/strong>\r\n\r\nPulmonary_Blood_Circulation<\/a> by Artwork by Holly Fischer from Open Michigan (Respiratory Tact Slide 20)<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.8<\/strong>\r\n\r\nsystemic_circuit.svg<\/a> by Surachit<\/a> on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/) license. (Derivative work based on SEER Training by NCI\/ U.S. Government<\/a>).\r\n\r\nFigure 14.2.9<\/strong>\r\n\r\nRed_White_Blood_cells<\/a> by Electron Microscopy Facility at The National Cancer Institute at Frederick (NCI-Frederick) on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\nReferences<\/h2>\r\n
Blausen.com Staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine<\/i>\u00a01<\/b>\u00a0(2).\u00a0DOI:10.15347\/wjm\/2014.010.\u00a0ISSN\u00a02002-4436<\/p>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 20.2 Cardiovascular circulation [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 7.3). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/20-1-structure-and-function-of-blood-vessels<\/p>\r\nBrainard, J\/ CK-12 Foundation. (2016). Figure 4 Diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system [digital image]. In CK-12 College Human Biology<\/em> (Section 16.2) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/16.2\/<\/p>\r\nCrashCourse. (2012, July 30). Circulatory & respiratory systems - CrashCourse Biology #27. YouTube. https:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=youtu.be<\/p>\r\n
Du, J. (2012, August). Brain vasculature formation [digital image]. PLoS Biology,<\/em> 10(8): ev10.i08. https:\/\/doi.org\/10.1371\/image.pbio.v10.i08 \u00a9 Chen.<\/p>\r\nMayo Clinic. (2013). The heart and circulatory system - How they work. YouTube. https:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU&t=1s<\/p>\r\n
TED-Ed. (2014, May 20). How the heart actually pumps blood - Edmond Hui. YouTube. https:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\nFigure 14.2.1 What are these strange tunnels?<\/em><\/figcaption><\/figure>\n\nAnt Hill or Plumbing System?<\/h1>\n<\/div>\n
What do you think the picture in Figure 14.2.1 shows? Is it a maze of underground passageways in an ant hill? A network of interconnected pipes in a complex plumbing system? The picture actually shows something that, like ant tunnels and plumbing pipes, functions as a transportation system. It shows a network of blood vessels, which are part of the cardiovascular system.<\/p>\n
\nWhat is the Cardiovascular System?<\/h1>\n<\/div>\n
The\u00a0cardiovascular system<\/a><\/strong>, also called the circulatory system, is the organ system that transports materials to and from all the cells of the body. The materials carried by the cardiovascular system include oxygen from the lungs<\/a>, nutrients from the digestive system<\/a>, hormones<\/a> from glands of the endocrine system<\/a>, and waste materials from cells throughout the body. Transport of these and many other materials is necessary to maintain homeostasis<\/a> of the body. The main components of the cardiovascular system are the heart, blood vessels, and blood. Each of these components is shown in Figure 14.2.2 and introduced below.<\/p>\nFigure 14.2.2 This simplified drawing of the cardiovascular system shows its main structures. The heart is shown in the chest in red. Blood vessels called arteries are also shown in red, and blood vessels called veins are shown in blue.<\/em><\/figcaption><\/figure>\n\nHeart<\/h1>\n<\/div>\n
The\u00a0heart<\/a><\/strong> is a muscular organ in the chest. It consists mainly of cardiac muscle<\/a> tissue, and it pumps blood through blood vessels by repeated, rhythmic contractions. As shown in Figure 14.2.3, the heart has four inner chambers: a right atrium and ventricle, and a left atrium and ventricle. On each side of the heart, blood is pumped from the atrium to the ventricle below it, and from the ventricle out of the heart. The heart also contains several valves that allow blood to flow only in the proper direction through the heart.<\/p>\nFigure 14.2.3 The right side of the heart includes the right atrium and right ventricle. The left side includes the left atrium and left ventricle.<\/em><\/figcaption><\/figure>\n <\/p>\n
As you may have noticed, the Figure 14.2.3 diagram labels the right side of the heart on the left side of the diagram, and vice versa.\u00a0 This is because it is assumed that in this diagram, the heart appears\u00a0 as if the patient was facing us – the patient’s left side is on our right side!<\/p>\n
Unlike skeletal muscle, cardiac muscle routinely contracts without stimulation by the\u00a0nervous system. Specialized cardiac muscle\u00a0cells\u00a0send out electrical impulses that stimulate the contractions. As a result, the atria and ventricles normally contract with just the right timing to keep blood pumping efficiently through the heart.<\/p>\n
\nBlood Vessels<\/h1>\n<\/div>\n
The blood vessels<\/a> of the cardiovascular system are like a network of interconnected, one-way roads that range from superhighways to back alleys. Like a network of roads, the blood vessels are tasked with allowing the transport of materials from one place to another. There are three major types of blood vessels: arteries, veins, and capillaries. They are illustrated in Figure 14.2.4 and described below.<\/p>\nFigure 14.2.4 This diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system.<\/em><\/figcaption><\/figure>\n\n- Arteries<\/a><\/strong>\u00a0are blood vessels that carry blood away from the heart (except for the arteries that actually supply blood to the heart muscle). Most arteries carry oxygen-rich blood, and one of their main functions is distributing oxygen to tissues throughout the body. The smallest arteries are called arterioles.<\/li>\n
- Veins<\/a><\/strong>\u00a0are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood. The smallest veins are called venules.<\/li>\n
- Capillaries<\/a><\/strong>\u00a0are the smallest blood vessels, and they connect arterioles and venules. As they pass through tissues, they exchange substances (including oxygen) with\u00a0cells.<\/li>\n<\/ul>\n\n
Two Circulations<\/h1>\n<\/div>\n
Cells throughout the body need a constant supply of oxygen. They get oxygen from capillaries in the systemic circulation. The systemic circulation is just one of two interconnected circulations that make up the human cardiovascular system. The other circulation is the pulmonary system, which is where blood picks up oxygen to carry to cells. It takes blood about 20 seconds to make one complete transit through both circulations (see Figure 14.2.5).<\/p>\nFigure 14.2.5 There are two main circuits through which blood flows in the cardiovascular system. In the pulmonary circuit, blood moves from the right side of the heart to the lungs and then back to the left side of the heart. In the systemic circuit, blood moves from the left side of the heart to the body tissues and then back to the right side of the heart.<\/em><\/figcaption><\/figure>\nPulmonary Circuit<\/h2>\n
The\u00a0pulmonary<\/strong>\u00a0<\/strong>circuit<\/strong><\/a> involves only the heart, the lungs, and the major blood vessels that connect them (illustrated in Figure 14.2.6). Blood moves through the pulmonary circuit from the heart, to the lungs, and then back to the heart again, becoming oxygenated in the process. Specifically, the right ventricle of the heart pumps deoxygenated blood into the right and left pulmonary arteries. These arteries carry the blood to the right and left lungs, respectively. Oxygenated blood then returns from the right and left lungs through the two right and two left pulmonary veins. All four pulmonary veins enter the left atrium of the heart.<\/p>\nFigure 14.2.6 This diagram shows the heart, lungs, and major vessels that make up the pulmonary circulation. The coloured arrows indicate the direction of blood flow \u2014 red for oxygenated blood and blue for relatively deoxygenated blood.<\/em><\/figcaption><\/figure>\nWhat happens to the blood while it is in the lungs? It passes through increasingly smaller arteries, and finally through capillary networks surrounding the alveoli (see Figure 14.2.7). This is where gas exchange takes place. The deoxygenated blood in the capillaries picks up oxygen from the alveoli, and gives up carbon dioxide to the alveoli. As a result, the blood returning to the heart in the pulmonary veins is almost completely saturated with oxygen.<\/p>\nFigure 14.2.7 This diagram illustrates clusters of alveoli in the lungs, where gas exchange takes place with blood in capillaries as it passes through the pulmonary circulation.<\/em><\/figcaption><\/figure>\nSystemic Circulation<\/h2>\n
The oxygenated blood that enters the left atrium of the heart in the pulmonary circulation then passes into the\u00a0systemic circuit<\/a>.<\/strong>\u00a0This is the part of the cardiovascular system that transports blood to and from all of the tissues of the body to provide oxygen and\u00a0nutrients, and to pick up wastes. It consists of the heart and blood vessels that supply the metabolic needs of all the cells in the body, including those of the heart and lungs.<\/p>\nAs shown in Figure 14.2.8, in the systemic circulation, the left atrium pumps oxygenated blood to the left ventricle, which pumps the blood directly into the aorta, the body\u2019s largest artery. Major arteries branching off the aorta carry the blood to the head and upper extremities. The aorta continues down through the abdomen and carries blood to the abdomen and lower extremities. The blood then returns to the heart through the network of increasingly larger veins of the systemic circulation. All of the returning blood eventually collects in the superior vena cava (upper body) and inferior vena cava (lower body), which empty directly into the right atrium of the heart.<\/p>\nFigure 14.2.8 The systemic circulation includes the aorta (red), which carries oxygenated blood away from the heart to the rest of the body; and the inferior and superior venae cavae (blue), which return deoxygenated blood to the heart from the body. The coloured arrows in the diagram indicate the direction of blood flow \u2014 red for oxygenated and blue for deoxygenated.<\/em><\/figcaption><\/figure>\nBlood<\/h2>\nFigure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em><\/figcaption><\/figure>\nBlood<\/a><\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0pH<\/a>, among other functions.<\/p>\nThe fluid part of blood is called\u00a0plasma<\/a><\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.<\/p>\n\n- Erythrocytes<\/a> <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0hemoglobin<\/a><\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\n
- Leukocytes<\/a> <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\n
- Thrombocytes<\/a><\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\n<\/ul>\n\n\n
\n14.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- The cardiovascular system<\/a> is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the heart<\/a>, blood vessels<\/a>, and blood<\/a>.<\/li>\n
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\n
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\n
- The cardiovascular system has two interconnected circulations. The pulmonary circuit<\/a> carries blood between the heart and lungs, where blood is oxygenated. The systemic circuit<\/a> carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\n
- Blood is a fluid connective tissue<\/a> that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0plasma<\/a> \u2014 which contains many dissolved substances, and cells, including erythrocytes<\/a>, leukocytes<\/a> and thrombocytes<\/a>.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n14.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the heart and how it functions.<\/li>\n
- Compare and contrast the pulmonary and systemic circulations.<\/li>\n
- \n\n
Heart<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"2987\"]heart[\/pb_glossary]<\/strong> is a muscular organ in the chest. It consists mainly of [pb_glossary id=\"5925\"]cardiac muscle[\/pb_glossary] tissue, and it pumps blood through blood vessels by repeated, rhythmic contractions. As shown in Figure 14.2.3, the heart has four inner chambers: a right atrium and ventricle, and a left atrium and ventricle. On each side of the heart, blood is pumped from the atrium to the ventricle below it, and from the ventricle out of the heart. The heart also contains several valves that allow blood to flow only in the proper direction through the heart.\r\n\r\n[caption id=\"attachment_4384\" align=\"aligncenter\" width=\"394\"] Figure 14.2.3 The right side of the heart includes the right atrium and right ventricle. The left side includes the left atrium and left ventricle.<\/em>[\/caption]\r\n\r\n \r\n\r\nAs you may have noticed, the Figure 14.2.3 diagram labels the right side of the heart on the left side of the diagram, and vice versa.\u00a0 This is because it is assumed that in this diagram, the heart appears\u00a0 as if the patient was facing us - the patient's left side is on our right side!\r\n\r\nUnlike skeletal muscle, cardiac muscle routinely contracts without stimulation by the\u00a0nervous system. Specialized cardiac muscle\u00a0cells\u00a0send out electrical impulses that stimulate the contractions. As a result, the atria and ventricles normally contract with just the right timing to keep blood pumping efficiently through the heart.\r\n\r\nBlood Vessels<\/h1>\r\n<\/div>\r\nThe [pb_glossary id=\"5835\"]blood vessels[\/pb_glossary] of the cardiovascular system are like a network of interconnected, one-way roads that range from superhighways to back alleys. Like a network of roads, the blood vessels are tasked with allowing the transport of materials from one place to another. There are three major types of blood vessels: arteries, veins, and capillaries. They are illustrated in Figure 14.2.4 and described below.\r\n\r\n[caption id=\"attachment_4388\" align=\"aligncenter\" width=\"500\"] Figure 14.2.4 This diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system.<\/em>[\/caption]\r\n\r\n \t- [pb_glossary id=\"4385\"]Arteries[\/pb_glossary]<\/strong>\u00a0are blood vessels that carry blood away from the heart (except for the arteries that actually supply blood to the heart muscle). Most arteries carry oxygen-rich blood, and one of their main functions is distributing oxygen to tissues throughout the body. The smallest arteries are called arterioles.<\/li>\r\n \t
- [pb_glossary id=\"4386\"]Veins[\/pb_glossary]<\/strong>\u00a0are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood. The smallest veins are called venules.<\/li>\r\n \t
- [pb_glossary id=\"5923\"]Capillaries[\/pb_glossary]<\/strong>\u00a0are the smallest blood vessels, and they connect arterioles and venules. As they pass through tissues, they exchange substances (including oxygen) with\u00a0cells.<\/li>\r\n<\/ul>\r\n\r\n
Two Circulations<\/h1>\r\n<\/div>\r\nCells throughout the body need a constant supply of oxygen. They get oxygen from capillaries in the systemic circulation. The systemic circulation is just one of two interconnected circulations that make up the human cardiovascular system. The other circulation is the pulmonary system, which is where blood picks up oxygen to carry to cells. It takes blood about 20 seconds to make one complete transit through both circulations (see Figure 14.2.5).\r\n\r\n[caption id=\"attachment_4389\" align=\"aligncenter\" width=\"927\"] Figure 14.2.5 There are two main circuits through which blood flows in the cardiovascular system. In the pulmonary circuit, blood moves from the right side of the heart to the lungs and then back to the left side of the heart. In the systemic circuit, blood moves from the left side of the heart to the body tissues and then back to the right side of the heart.<\/em>[\/caption]\r\nPulmonary Circuit<\/h2>\r\nThe\u00a0[pb_glossary id=\"4387\"]pulmonary<\/strong>\u00a0<\/strong>circuit<\/strong>[\/pb_glossary] involves only the heart, the lungs, and the major blood vessels that connect them (illustrated in Figure 14.2.6). Blood moves through the pulmonary circuit from the heart, to the lungs, and then back to the heart again, becoming oxygenated in the process. Specifically, the right ventricle of the heart pumps deoxygenated blood into the right and left pulmonary arteries. These arteries carry the blood to the right and left lungs, respectively. Oxygenated blood then returns from the right and left lungs through the two right and two left pulmonary veins. All four pulmonary veins enter the left atrium of the heart.\r\n\r\n[caption id=\"attachment_4391\" align=\"aligncenter\" width=\"520\"] Figure 14.2.6 This diagram shows the heart, lungs, and major vessels that make up the pulmonary circulation. The coloured arrows indicate the direction of blood flow \u2014 red for oxygenated blood and blue for relatively deoxygenated blood.<\/em>[\/caption]\r\n\r\nWhat happens to the blood while it is in the lungs? It passes through increasingly smaller arteries, and finally through capillary networks surrounding the alveoli (see Figure 14.2.7). This is where gas exchange takes place. The deoxygenated blood in the capillaries picks up oxygen from the alveoli, and gives up carbon dioxide to the alveoli. As a result, the blood returning to the heart in the pulmonary veins is almost completely saturated with oxygen.\r\n\r\n[caption id=\"attachment_4392\" align=\"aligncenter\" width=\"812\"] Figure 14.2.7 This diagram illustrates clusters of alveoli in the lungs, where gas exchange takes place with blood in capillaries as it passes through the pulmonary circulation.<\/em>[\/caption]\r\nSystemic Circulation<\/h2>\r\nThe oxygenated blood that enters the left atrium of the heart in the pulmonary circulation then passes into the\u00a0[pb_glossary id=\"4393\"]systemic circuit[\/pb_glossary].<\/strong>\u00a0This is the part of the cardiovascular system that transports blood to and from all of the tissues of the body to provide oxygen and\u00a0nutrients, and to pick up wastes. It consists of the heart and blood vessels that supply the metabolic needs of all the cells in the body, including those of the heart and lungs.\r\n\r\nAs shown in Figure 14.2.8, in the systemic circulation, the left atrium pumps oxygenated blood to the left ventricle, which pumps the blood directly into the aorta, the body\u2019s largest artery. Major arteries branching off the aorta carry the blood to the head and upper extremities. The aorta continues down through the abdomen and carries blood to the abdomen and lower extremities. The blood then returns to the heart through the network of increasingly larger veins of the systemic circulation. All of the returning blood eventually collects in the superior vena cava (upper body) and inferior vena cava (lower body), which empty directly into the right atrium of the heart.\r\n\r\n[caption id=\"attachment_4394\" align=\"aligncenter\" width=\"566\"] Figure 14.2.8 The systemic circulation includes the aorta (red), which carries oxygenated blood away from the heart to the rest of the body; and the inferior and superior venae cavae (blue), which return deoxygenated blood to the heart from the body. The coloured arrows in the diagram indicate the direction of blood flow \u2014 red for oxygenated and blue for deoxygenated.<\/em>[\/caption]\r\nBlood<\/h2>\r\n[caption id=\"attachment_4396\" align=\"alignright\" width=\"500\"] Figure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em>[\/caption]\r\n\r\n[pb_glossary id=\"2702\"]Blood[\/pb_glossary]<\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0[pb_glossary id=\"4330\"]pH[\/pb_glossary], among other functions.\r\n\r\nThe fluid part of blood is called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary]<\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.\r\n\r\n \t- [pb_glossary id=\"4398\"]Erythrocytes[\/pb_glossary] <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0[pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary]<\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\r\n \t
- [pb_glossary id=\"5623\"]Leukocytes[\/pb_glossary] <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\r\n \t
- [pb_glossary id=\"4399\"]Thrombocytes[\/pb_glossary]<\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\r\n<\/ul>\r\n\r\n
\r\n14.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5927\"]cardiovascular system[\/pb_glossary] is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the [pb_glossary id=\"2987\"]heart[\/pb_glossary], [pb_glossary id=\"5835\"]blood vessels[\/pb_glossary], and [pb_glossary id=\"2702\"]blood[\/pb_glossary].<\/li>\r\n \t
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\r\n \t
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\r\n \t
- The cardiovascular system has two interconnected circulations. The [pb_glossary id=\"4387\"]pulmonary circuit[\/pb_glossary] carries blood between the heart and lungs, where blood is oxygenated. The [pb_glossary id=\"4393\"]systemic circuit[\/pb_glossary] carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\r\n \t
- Blood is a [pb_glossary id=\"4402\"]fluid connective tissue[\/pb_glossary] that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary] \u2014 which contains many dissolved substances, and cells, including [pb_glossary id=\"4398\"]erythrocytes[\/pb_glossary], [pb_glossary id=\"5623\"]leukocytes[\/pb_glossary] and [pb_glossary id=\"4399\"]thrombocytes[\/pb_glossary].<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n14.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the heart and how it functions.<\/li>\r\n \t
- Compare and contrast the pulmonary and systemic circulations.<\/li>\r\n \t
- [h5p id=\"612\"]<\/li>\r\n \t
- What is blood? What are its chief constituents?<\/li>\r\n \t
- Name three different types of substances transported by the cardiovascular system.<\/li>\r\n \t
- Explain why the heart and lungs need blood from the systemic circulation.<\/li>\r\n \t
- Do blood vessels carrying deoxygenated blood from the body back to the heart get increasingly larger or smaller?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n14.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=emb_logo\r\nHow the heart actually pumps blood - Edmond Hui, TED-Ed, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=emb_logo\r\n
Circulatory & Respiratory Systems - CrashCourse Biology #27, CrashCourse, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU\r\n
The Heart and Circulatory System - How They Work, Mayo Clinic, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 14.2.1<\/strong>\r\n\r\nBrain vascular formation<\/a> [photo] by Liulin Du\/ Chen (The National Cancer Institute at Frederick) on PLOS Biology<\/a> is used under a CC BY 4.0<\/a> license.\r\n\r\nFigure 14.2.2<\/strong>\r\n\r\nCirculatory_System_no_tags.svg<\/a> by Mariana Ruiz Villarreal [LadyofHats]<\/a> on Wikimedia Commons is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.3<\/strong>\r\n\r\nBlausen_0462_HeartAnatomy<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0)\r\n\r\nFigure 14.2.4<\/strong>\r\n\r\nStructure and functions of the different types of blood vessels<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\r\nFigure 14.2.5<\/strong>\r\n\r\n2101_Blood_Flow_Through_the_Heart<\/a>\u00a0by OpenStax College<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.6<\/strong>\r\n\r\nIllu_pulmonary_circuit<\/a> by Arcadian<\/a> from National Cancer Institute\/ SEER Training<\/a> on Wikimedia Commons is in the the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.7<\/strong>\r\n\r\nPulmonary_Blood_Circulation<\/a> by Artwork by Holly Fischer from Open Michigan (Respiratory Tact Slide 20)<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.8<\/strong>\r\n\r\nsystemic_circuit.svg<\/a> by Surachit<\/a> on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/) license. (Derivative work based on SEER Training by NCI\/ U.S. Government<\/a>).\r\n\r\nFigure 14.2.9<\/strong>\r\n\r\nRed_White_Blood_cells<\/a> by Electron Microscopy Facility at The National Cancer Institute at Frederick (NCI-Frederick) on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\nReferences<\/h2>\r\n
Blausen.com Staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine<\/i>\u00a01<\/b>\u00a0(2).\u00a0DOI:10.15347\/wjm\/2014.010.\u00a0ISSN\u00a02002-4436<\/p>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 20.2 Cardiovascular circulation [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 7.3). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/20-1-structure-and-function-of-blood-vessels<\/p>\r\nBrainard, J\/ CK-12 Foundation. (2016). Figure 4 Diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system [digital image]. In CK-12 College Human Biology<\/em> (Section 16.2) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/16.2\/<\/p>\r\nCrashCourse. (2012, July 30). Circulatory & respiratory systems - CrashCourse Biology #27. YouTube. https:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=youtu.be<\/p>\r\n
Du, J. (2012, August). Brain vasculature formation [digital image]. PLoS Biology,<\/em> 10(8): ev10.i08. https:\/\/doi.org\/10.1371\/image.pbio.v10.i08 \u00a9 Chen.<\/p>\r\nMayo Clinic. (2013). The heart and circulatory system - How they work. YouTube. https:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU&t=1s<\/p>\r\n
TED-Ed. (2014, May 20). How the heart actually pumps blood - Edmond Hui. YouTube. https:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\nFigure 14.2.1 What are these strange tunnels?<\/em><\/figcaption><\/figure>\n\nAnt Hill or Plumbing System?<\/h1>\n<\/div>\n
What do you think the picture in Figure 14.2.1 shows? Is it a maze of underground passageways in an ant hill? A network of interconnected pipes in a complex plumbing system? The picture actually shows something that, like ant tunnels and plumbing pipes, functions as a transportation system. It shows a network of blood vessels, which are part of the cardiovascular system.<\/p>\n
\nWhat is the Cardiovascular System?<\/h1>\n<\/div>\n
The\u00a0cardiovascular system<\/a><\/strong>, also called the circulatory system, is the organ system that transports materials to and from all the cells of the body. The materials carried by the cardiovascular system include oxygen from the lungs<\/a>, nutrients from the digestive system<\/a>, hormones<\/a> from glands of the endocrine system<\/a>, and waste materials from cells throughout the body. Transport of these and many other materials is necessary to maintain homeostasis<\/a> of the body. The main components of the cardiovascular system are the heart, blood vessels, and blood. Each of these components is shown in Figure 14.2.2 and introduced below.<\/p>\nFigure 14.2.2 This simplified drawing of the cardiovascular system shows its main structures. The heart is shown in the chest in red. Blood vessels called arteries are also shown in red, and blood vessels called veins are shown in blue.<\/em><\/figcaption><\/figure>\n\nHeart<\/h1>\n<\/div>\n
The\u00a0heart<\/a><\/strong> is a muscular organ in the chest. It consists mainly of cardiac muscle<\/a> tissue, and it pumps blood through blood vessels by repeated, rhythmic contractions. As shown in Figure 14.2.3, the heart has four inner chambers: a right atrium and ventricle, and a left atrium and ventricle. On each side of the heart, blood is pumped from the atrium to the ventricle below it, and from the ventricle out of the heart. The heart also contains several valves that allow blood to flow only in the proper direction through the heart.<\/p>\nFigure 14.2.3 The right side of the heart includes the right atrium and right ventricle. The left side includes the left atrium and left ventricle.<\/em><\/figcaption><\/figure>\n <\/p>\n
As you may have noticed, the Figure 14.2.3 diagram labels the right side of the heart on the left side of the diagram, and vice versa.\u00a0 This is because it is assumed that in this diagram, the heart appears\u00a0 as if the patient was facing us – the patient’s left side is on our right side!<\/p>\n
Unlike skeletal muscle, cardiac muscle routinely contracts without stimulation by the\u00a0nervous system. Specialized cardiac muscle\u00a0cells\u00a0send out electrical impulses that stimulate the contractions. As a result, the atria and ventricles normally contract with just the right timing to keep blood pumping efficiently through the heart.<\/p>\n
\nBlood Vessels<\/h1>\n<\/div>\n
The blood vessels<\/a> of the cardiovascular system are like a network of interconnected, one-way roads that range from superhighways to back alleys. Like a network of roads, the blood vessels are tasked with allowing the transport of materials from one place to another. There are three major types of blood vessels: arteries, veins, and capillaries. They are illustrated in Figure 14.2.4 and described below.<\/p>\nFigure 14.2.4 This diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system.<\/em><\/figcaption><\/figure>\n\n- Arteries<\/a><\/strong>\u00a0are blood vessels that carry blood away from the heart (except for the arteries that actually supply blood to the heart muscle). Most arteries carry oxygen-rich blood, and one of their main functions is distributing oxygen to tissues throughout the body. The smallest arteries are called arterioles.<\/li>\n
- Veins<\/a><\/strong>\u00a0are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood. The smallest veins are called venules.<\/li>\n
- Capillaries<\/a><\/strong>\u00a0are the smallest blood vessels, and they connect arterioles and venules. As they pass through tissues, they exchange substances (including oxygen) with\u00a0cells.<\/li>\n<\/ul>\n\n
Two Circulations<\/h1>\n<\/div>\n
Cells throughout the body need a constant supply of oxygen. They get oxygen from capillaries in the systemic circulation. The systemic circulation is just one of two interconnected circulations that make up the human cardiovascular system. The other circulation is the pulmonary system, which is where blood picks up oxygen to carry to cells. It takes blood about 20 seconds to make one complete transit through both circulations (see Figure 14.2.5).<\/p>\nFigure 14.2.5 There are two main circuits through which blood flows in the cardiovascular system. In the pulmonary circuit, blood moves from the right side of the heart to the lungs and then back to the left side of the heart. In the systemic circuit, blood moves from the left side of the heart to the body tissues and then back to the right side of the heart.<\/em><\/figcaption><\/figure>\nPulmonary Circuit<\/h2>\n
The\u00a0pulmonary<\/strong>\u00a0<\/strong>circuit<\/strong><\/a> involves only the heart, the lungs, and the major blood vessels that connect them (illustrated in Figure 14.2.6). Blood moves through the pulmonary circuit from the heart, to the lungs, and then back to the heart again, becoming oxygenated in the process. Specifically, the right ventricle of the heart pumps deoxygenated blood into the right and left pulmonary arteries. These arteries carry the blood to the right and left lungs, respectively. Oxygenated blood then returns from the right and left lungs through the two right and two left pulmonary veins. All four pulmonary veins enter the left atrium of the heart.<\/p>\nFigure 14.2.6 This diagram shows the heart, lungs, and major vessels that make up the pulmonary circulation. The coloured arrows indicate the direction of blood flow \u2014 red for oxygenated blood and blue for relatively deoxygenated blood.<\/em><\/figcaption><\/figure>\nWhat happens to the blood while it is in the lungs? It passes through increasingly smaller arteries, and finally through capillary networks surrounding the alveoli (see Figure 14.2.7). This is where gas exchange takes place. The deoxygenated blood in the capillaries picks up oxygen from the alveoli, and gives up carbon dioxide to the alveoli. As a result, the blood returning to the heart in the pulmonary veins is almost completely saturated with oxygen.<\/p>\nFigure 14.2.7 This diagram illustrates clusters of alveoli in the lungs, where gas exchange takes place with blood in capillaries as it passes through the pulmonary circulation.<\/em><\/figcaption><\/figure>\nSystemic Circulation<\/h2>\n
The oxygenated blood that enters the left atrium of the heart in the pulmonary circulation then passes into the\u00a0systemic circuit<\/a>.<\/strong>\u00a0This is the part of the cardiovascular system that transports blood to and from all of the tissues of the body to provide oxygen and\u00a0nutrients, and to pick up wastes. It consists of the heart and blood vessels that supply the metabolic needs of all the cells in the body, including those of the heart and lungs.<\/p>\nAs shown in Figure 14.2.8, in the systemic circulation, the left atrium pumps oxygenated blood to the left ventricle, which pumps the blood directly into the aorta, the body\u2019s largest artery. Major arteries branching off the aorta carry the blood to the head and upper extremities. The aorta continues down through the abdomen and carries blood to the abdomen and lower extremities. The blood then returns to the heart through the network of increasingly larger veins of the systemic circulation. All of the returning blood eventually collects in the superior vena cava (upper body) and inferior vena cava (lower body), which empty directly into the right atrium of the heart.<\/p>\nFigure 14.2.8 The systemic circulation includes the aorta (red), which carries oxygenated blood away from the heart to the rest of the body; and the inferior and superior venae cavae (blue), which return deoxygenated blood to the heart from the body. The coloured arrows in the diagram indicate the direction of blood flow \u2014 red for oxygenated and blue for deoxygenated.<\/em><\/figcaption><\/figure>\nBlood<\/h2>\nFigure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em><\/figcaption><\/figure>\nBlood<\/a><\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0pH<\/a>, among other functions.<\/p>\nThe fluid part of blood is called\u00a0plasma<\/a><\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.<\/p>\n\n- Erythrocytes<\/a> <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0hemoglobin<\/a><\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\n
- Leukocytes<\/a> <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\n
- Thrombocytes<\/a><\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\n<\/ul>\n\n\n
\n14.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- The cardiovascular system<\/a> is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the heart<\/a>, blood vessels<\/a>, and blood<\/a>.<\/li>\n
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\n
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\n
- The cardiovascular system has two interconnected circulations. The pulmonary circuit<\/a> carries blood between the heart and lungs, where blood is oxygenated. The systemic circuit<\/a> carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\n
- Blood is a fluid connective tissue<\/a> that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0plasma<\/a> \u2014 which contains many dissolved substances, and cells, including erythrocytes<\/a>, leukocytes<\/a> and thrombocytes<\/a>.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n14.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the heart and how it functions.<\/li>\n
- Compare and contrast the pulmonary and systemic circulations.<\/li>\n
- \n\n
Blood Vessels<\/h1>\r\n<\/div>\r\nThe [pb_glossary id=\"5835\"]blood vessels[\/pb_glossary] of the cardiovascular system are like a network of interconnected, one-way roads that range from superhighways to back alleys. Like a network of roads, the blood vessels are tasked with allowing the transport of materials from one place to another. There are three major types of blood vessels: arteries, veins, and capillaries. They are illustrated in Figure 14.2.4 and described below.\r\n\r\n[caption id=\"attachment_4388\" align=\"aligncenter\" width=\"500\"] Figure 14.2.4 This diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system.<\/em>[\/caption]\r\n\r\n \t- [pb_glossary id=\"4385\"]Arteries[\/pb_glossary]<\/strong>\u00a0are blood vessels that carry blood away from the heart (except for the arteries that actually supply blood to the heart muscle). Most arteries carry oxygen-rich blood, and one of their main functions is distributing oxygen to tissues throughout the body. The smallest arteries are called arterioles.<\/li>\r\n \t
- [pb_glossary id=\"4386\"]Veins[\/pb_glossary]<\/strong>\u00a0are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood. The smallest veins are called venules.<\/li>\r\n \t
- [pb_glossary id=\"5923\"]Capillaries[\/pb_glossary]<\/strong>\u00a0are the smallest blood vessels, and they connect arterioles and venules. As they pass through tissues, they exchange substances (including oxygen) with\u00a0cells.<\/li>\r\n<\/ul>\r\n\r\n
Two Circulations<\/h1>\r\n<\/div>\r\nCells throughout the body need a constant supply of oxygen. They get oxygen from capillaries in the systemic circulation. The systemic circulation is just one of two interconnected circulations that make up the human cardiovascular system. The other circulation is the pulmonary system, which is where blood picks up oxygen to carry to cells. It takes blood about 20 seconds to make one complete transit through both circulations (see Figure 14.2.5).\r\n\r\n[caption id=\"attachment_4389\" align=\"aligncenter\" width=\"927\"] Figure 14.2.5 There are two main circuits through which blood flows in the cardiovascular system. In the pulmonary circuit, blood moves from the right side of the heart to the lungs and then back to the left side of the heart. In the systemic circuit, blood moves from the left side of the heart to the body tissues and then back to the right side of the heart.<\/em>[\/caption]\r\nPulmonary Circuit<\/h2>\r\nThe\u00a0[pb_glossary id=\"4387\"]pulmonary<\/strong>\u00a0<\/strong>circuit<\/strong>[\/pb_glossary] involves only the heart, the lungs, and the major blood vessels that connect them (illustrated in Figure 14.2.6). Blood moves through the pulmonary circuit from the heart, to the lungs, and then back to the heart again, becoming oxygenated in the process. Specifically, the right ventricle of the heart pumps deoxygenated blood into the right and left pulmonary arteries. These arteries carry the blood to the right and left lungs, respectively. Oxygenated blood then returns from the right and left lungs through the two right and two left pulmonary veins. All four pulmonary veins enter the left atrium of the heart.\r\n\r\n[caption id=\"attachment_4391\" align=\"aligncenter\" width=\"520\"] Figure 14.2.6 This diagram shows the heart, lungs, and major vessels that make up the pulmonary circulation. The coloured arrows indicate the direction of blood flow \u2014 red for oxygenated blood and blue for relatively deoxygenated blood.<\/em>[\/caption]\r\n\r\nWhat happens to the blood while it is in the lungs? It passes through increasingly smaller arteries, and finally through capillary networks surrounding the alveoli (see Figure 14.2.7). This is where gas exchange takes place. The deoxygenated blood in the capillaries picks up oxygen from the alveoli, and gives up carbon dioxide to the alveoli. As a result, the blood returning to the heart in the pulmonary veins is almost completely saturated with oxygen.\r\n\r\n[caption id=\"attachment_4392\" align=\"aligncenter\" width=\"812\"] Figure 14.2.7 This diagram illustrates clusters of alveoli in the lungs, where gas exchange takes place with blood in capillaries as it passes through the pulmonary circulation.<\/em>[\/caption]\r\nSystemic Circulation<\/h2>\r\nThe oxygenated blood that enters the left atrium of the heart in the pulmonary circulation then passes into the\u00a0[pb_glossary id=\"4393\"]systemic circuit[\/pb_glossary].<\/strong>\u00a0This is the part of the cardiovascular system that transports blood to and from all of the tissues of the body to provide oxygen and\u00a0nutrients, and to pick up wastes. It consists of the heart and blood vessels that supply the metabolic needs of all the cells in the body, including those of the heart and lungs.\r\n\r\nAs shown in Figure 14.2.8, in the systemic circulation, the left atrium pumps oxygenated blood to the left ventricle, which pumps the blood directly into the aorta, the body\u2019s largest artery. Major arteries branching off the aorta carry the blood to the head and upper extremities. The aorta continues down through the abdomen and carries blood to the abdomen and lower extremities. The blood then returns to the heart through the network of increasingly larger veins of the systemic circulation. All of the returning blood eventually collects in the superior vena cava (upper body) and inferior vena cava (lower body), which empty directly into the right atrium of the heart.\r\n\r\n[caption id=\"attachment_4394\" align=\"aligncenter\" width=\"566\"] Figure 14.2.8 The systemic circulation includes the aorta (red), which carries oxygenated blood away from the heart to the rest of the body; and the inferior and superior venae cavae (blue), which return deoxygenated blood to the heart from the body. The coloured arrows in the diagram indicate the direction of blood flow \u2014 red for oxygenated and blue for deoxygenated.<\/em>[\/caption]\r\nBlood<\/h2>\r\n[caption id=\"attachment_4396\" align=\"alignright\" width=\"500\"] Figure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em>[\/caption]\r\n\r\n[pb_glossary id=\"2702\"]Blood[\/pb_glossary]<\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0[pb_glossary id=\"4330\"]pH[\/pb_glossary], among other functions.\r\n\r\nThe fluid part of blood is called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary]<\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.\r\n\r\n \t- [pb_glossary id=\"4398\"]Erythrocytes[\/pb_glossary] <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0[pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary]<\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\r\n \t
- [pb_glossary id=\"5623\"]Leukocytes[\/pb_glossary] <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\r\n \t
- [pb_glossary id=\"4399\"]Thrombocytes[\/pb_glossary]<\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\r\n<\/ul>\r\n\r\n
\r\n14.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5927\"]cardiovascular system[\/pb_glossary] is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the [pb_glossary id=\"2987\"]heart[\/pb_glossary], [pb_glossary id=\"5835\"]blood vessels[\/pb_glossary], and [pb_glossary id=\"2702\"]blood[\/pb_glossary].<\/li>\r\n \t
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\r\n \t
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\r\n \t
- The cardiovascular system has two interconnected circulations. The [pb_glossary id=\"4387\"]pulmonary circuit[\/pb_glossary] carries blood between the heart and lungs, where blood is oxygenated. The [pb_glossary id=\"4393\"]systemic circuit[\/pb_glossary] carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\r\n \t
- Blood is a [pb_glossary id=\"4402\"]fluid connective tissue[\/pb_glossary] that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary] \u2014 which contains many dissolved substances, and cells, including [pb_glossary id=\"4398\"]erythrocytes[\/pb_glossary], [pb_glossary id=\"5623\"]leukocytes[\/pb_glossary] and [pb_glossary id=\"4399\"]thrombocytes[\/pb_glossary].<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n14.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the heart and how it functions.<\/li>\r\n \t
- Compare and contrast the pulmonary and systemic circulations.<\/li>\r\n \t
- [h5p id=\"612\"]<\/li>\r\n \t
- What is blood? What are its chief constituents?<\/li>\r\n \t
- Name three different types of substances transported by the cardiovascular system.<\/li>\r\n \t
- Explain why the heart and lungs need blood from the systemic circulation.<\/li>\r\n \t
- Do blood vessels carrying deoxygenated blood from the body back to the heart get increasingly larger or smaller?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n14.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=emb_logo\r\nHow the heart actually pumps blood - Edmond Hui, TED-Ed, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=emb_logo\r\n
Circulatory & Respiratory Systems - CrashCourse Biology #27, CrashCourse, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU\r\n
The Heart and Circulatory System - How They Work, Mayo Clinic, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 14.2.1<\/strong>\r\n\r\nBrain vascular formation<\/a> [photo] by Liulin Du\/ Chen (The National Cancer Institute at Frederick) on PLOS Biology<\/a> is used under a CC BY 4.0<\/a> license.\r\n\r\nFigure 14.2.2<\/strong>\r\n\r\nCirculatory_System_no_tags.svg<\/a> by Mariana Ruiz Villarreal [LadyofHats]<\/a> on Wikimedia Commons is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.3<\/strong>\r\n\r\nBlausen_0462_HeartAnatomy<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0)\r\n\r\nFigure 14.2.4<\/strong>\r\n\r\nStructure and functions of the different types of blood vessels<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\r\nFigure 14.2.5<\/strong>\r\n\r\n2101_Blood_Flow_Through_the_Heart<\/a>\u00a0by OpenStax College<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.6<\/strong>\r\n\r\nIllu_pulmonary_circuit<\/a> by Arcadian<\/a> from National Cancer Institute\/ SEER Training<\/a> on Wikimedia Commons is in the the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.7<\/strong>\r\n\r\nPulmonary_Blood_Circulation<\/a> by Artwork by Holly Fischer from Open Michigan (Respiratory Tact Slide 20)<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.8<\/strong>\r\n\r\nsystemic_circuit.svg<\/a> by Surachit<\/a> on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/) license. (Derivative work based on SEER Training by NCI\/ U.S. Government<\/a>).\r\n\r\nFigure 14.2.9<\/strong>\r\n\r\nRed_White_Blood_cells<\/a> by Electron Microscopy Facility at The National Cancer Institute at Frederick (NCI-Frederick) on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\nReferences<\/h2>\r\n
Blausen.com Staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine<\/i>\u00a01<\/b>\u00a0(2).\u00a0DOI:10.15347\/wjm\/2014.010.\u00a0ISSN\u00a02002-4436<\/p>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 20.2 Cardiovascular circulation [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 7.3). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/20-1-structure-and-function-of-blood-vessels<\/p>\r\nBrainard, J\/ CK-12 Foundation. (2016). Figure 4 Diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system [digital image]. In CK-12 College Human Biology<\/em> (Section 16.2) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/16.2\/<\/p>\r\nCrashCourse. (2012, July 30). Circulatory & respiratory systems - CrashCourse Biology #27. YouTube. https:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=youtu.be<\/p>\r\n
Du, J. (2012, August). Brain vasculature formation [digital image]. PLoS Biology,<\/em> 10(8): ev10.i08. https:\/\/doi.org\/10.1371\/image.pbio.v10.i08 \u00a9 Chen.<\/p>\r\nMayo Clinic. (2013). The heart and circulatory system - How they work. YouTube. https:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU&t=1s<\/p>\r\n
TED-Ed. (2014, May 20). How the heart actually pumps blood - Edmond Hui. YouTube. https:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\nFigure 14.2.1 What are these strange tunnels?<\/em><\/figcaption><\/figure>\n\nAnt Hill or Plumbing System?<\/h1>\n<\/div>\n
What do you think the picture in Figure 14.2.1 shows? Is it a maze of underground passageways in an ant hill? A network of interconnected pipes in a complex plumbing system? The picture actually shows something that, like ant tunnels and plumbing pipes, functions as a transportation system. It shows a network of blood vessels, which are part of the cardiovascular system.<\/p>\n
\nWhat is the Cardiovascular System?<\/h1>\n<\/div>\n
The\u00a0cardiovascular system<\/a><\/strong>, also called the circulatory system, is the organ system that transports materials to and from all the cells of the body. The materials carried by the cardiovascular system include oxygen from the lungs<\/a>, nutrients from the digestive system<\/a>, hormones<\/a> from glands of the endocrine system<\/a>, and waste materials from cells throughout the body. Transport of these and many other materials is necessary to maintain homeostasis<\/a> of the body. The main components of the cardiovascular system are the heart, blood vessels, and blood. Each of these components is shown in Figure 14.2.2 and introduced below.<\/p>\nFigure 14.2.2 This simplified drawing of the cardiovascular system shows its main structures. The heart is shown in the chest in red. Blood vessels called arteries are also shown in red, and blood vessels called veins are shown in blue.<\/em><\/figcaption><\/figure>\n\nHeart<\/h1>\n<\/div>\n
The\u00a0heart<\/a><\/strong> is a muscular organ in the chest. It consists mainly of cardiac muscle<\/a> tissue, and it pumps blood through blood vessels by repeated, rhythmic contractions. As shown in Figure 14.2.3, the heart has four inner chambers: a right atrium and ventricle, and a left atrium and ventricle. On each side of the heart, blood is pumped from the atrium to the ventricle below it, and from the ventricle out of the heart. The heart also contains several valves that allow blood to flow only in the proper direction through the heart.<\/p>\nFigure 14.2.3 The right side of the heart includes the right atrium and right ventricle. The left side includes the left atrium and left ventricle.<\/em><\/figcaption><\/figure>\n <\/p>\n
As you may have noticed, the Figure 14.2.3 diagram labels the right side of the heart on the left side of the diagram, and vice versa.\u00a0 This is because it is assumed that in this diagram, the heart appears\u00a0 as if the patient was facing us – the patient’s left side is on our right side!<\/p>\n
Unlike skeletal muscle, cardiac muscle routinely contracts without stimulation by the\u00a0nervous system. Specialized cardiac muscle\u00a0cells\u00a0send out electrical impulses that stimulate the contractions. As a result, the atria and ventricles normally contract with just the right timing to keep blood pumping efficiently through the heart.<\/p>\n
\nBlood Vessels<\/h1>\n<\/div>\n
The blood vessels<\/a> of the cardiovascular system are like a network of interconnected, one-way roads that range from superhighways to back alleys. Like a network of roads, the blood vessels are tasked with allowing the transport of materials from one place to another. There are three major types of blood vessels: arteries, veins, and capillaries. They are illustrated in Figure 14.2.4 and described below.<\/p>\nFigure 14.2.4 This diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system.<\/em><\/figcaption><\/figure>\n\n- Arteries<\/a><\/strong>\u00a0are blood vessels that carry blood away from the heart (except for the arteries that actually supply blood to the heart muscle). Most arteries carry oxygen-rich blood, and one of their main functions is distributing oxygen to tissues throughout the body. The smallest arteries are called arterioles.<\/li>\n
- Veins<\/a><\/strong>\u00a0are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood. The smallest veins are called venules.<\/li>\n
- Capillaries<\/a><\/strong>\u00a0are the smallest blood vessels, and they connect arterioles and venules. As they pass through tissues, they exchange substances (including oxygen) with\u00a0cells.<\/li>\n<\/ul>\n\n
Two Circulations<\/h1>\n<\/div>\n
Cells throughout the body need a constant supply of oxygen. They get oxygen from capillaries in the systemic circulation. The systemic circulation is just one of two interconnected circulations that make up the human cardiovascular system. The other circulation is the pulmonary system, which is where blood picks up oxygen to carry to cells. It takes blood about 20 seconds to make one complete transit through both circulations (see Figure 14.2.5).<\/p>\nFigure 14.2.5 There are two main circuits through which blood flows in the cardiovascular system. In the pulmonary circuit, blood moves from the right side of the heart to the lungs and then back to the left side of the heart. In the systemic circuit, blood moves from the left side of the heart to the body tissues and then back to the right side of the heart.<\/em><\/figcaption><\/figure>\nPulmonary Circuit<\/h2>\n
The\u00a0pulmonary<\/strong>\u00a0<\/strong>circuit<\/strong><\/a> involves only the heart, the lungs, and the major blood vessels that connect them (illustrated in Figure 14.2.6). Blood moves through the pulmonary circuit from the heart, to the lungs, and then back to the heart again, becoming oxygenated in the process. Specifically, the right ventricle of the heart pumps deoxygenated blood into the right and left pulmonary arteries. These arteries carry the blood to the right and left lungs, respectively. Oxygenated blood then returns from the right and left lungs through the two right and two left pulmonary veins. All four pulmonary veins enter the left atrium of the heart.<\/p>\nFigure 14.2.6 This diagram shows the heart, lungs, and major vessels that make up the pulmonary circulation. The coloured arrows indicate the direction of blood flow \u2014 red for oxygenated blood and blue for relatively deoxygenated blood.<\/em><\/figcaption><\/figure>\nWhat happens to the blood while it is in the lungs? It passes through increasingly smaller arteries, and finally through capillary networks surrounding the alveoli (see Figure 14.2.7). This is where gas exchange takes place. The deoxygenated blood in the capillaries picks up oxygen from the alveoli, and gives up carbon dioxide to the alveoli. As a result, the blood returning to the heart in the pulmonary veins is almost completely saturated with oxygen.<\/p>\nFigure 14.2.7 This diagram illustrates clusters of alveoli in the lungs, where gas exchange takes place with blood in capillaries as it passes through the pulmonary circulation.<\/em><\/figcaption><\/figure>\nSystemic Circulation<\/h2>\n
The oxygenated blood that enters the left atrium of the heart in the pulmonary circulation then passes into the\u00a0systemic circuit<\/a>.<\/strong>\u00a0This is the part of the cardiovascular system that transports blood to and from all of the tissues of the body to provide oxygen and\u00a0nutrients, and to pick up wastes. It consists of the heart and blood vessels that supply the metabolic needs of all the cells in the body, including those of the heart and lungs.<\/p>\nAs shown in Figure 14.2.8, in the systemic circulation, the left atrium pumps oxygenated blood to the left ventricle, which pumps the blood directly into the aorta, the body\u2019s largest artery. Major arteries branching off the aorta carry the blood to the head and upper extremities. The aorta continues down through the abdomen and carries blood to the abdomen and lower extremities. The blood then returns to the heart through the network of increasingly larger veins of the systemic circulation. All of the returning blood eventually collects in the superior vena cava (upper body) and inferior vena cava (lower body), which empty directly into the right atrium of the heart.<\/p>\nFigure 14.2.8 The systemic circulation includes the aorta (red), which carries oxygenated blood away from the heart to the rest of the body; and the inferior and superior venae cavae (blue), which return deoxygenated blood to the heart from the body. The coloured arrows in the diagram indicate the direction of blood flow \u2014 red for oxygenated and blue for deoxygenated.<\/em><\/figcaption><\/figure>\nBlood<\/h2>\nFigure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em><\/figcaption><\/figure>\nBlood<\/a><\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0pH<\/a>, among other functions.<\/p>\nThe fluid part of blood is called\u00a0plasma<\/a><\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.<\/p>\n\n- Erythrocytes<\/a> <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0hemoglobin<\/a><\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\n
- Leukocytes<\/a> <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\n
- Thrombocytes<\/a><\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\n<\/ul>\n\n\n
\n14.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- The cardiovascular system<\/a> is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the heart<\/a>, blood vessels<\/a>, and blood<\/a>.<\/li>\n
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\n
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\n
- The cardiovascular system has two interconnected circulations. The pulmonary circuit<\/a> carries blood between the heart and lungs, where blood is oxygenated. The systemic circuit<\/a> carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\n
- Blood is a fluid connective tissue<\/a> that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0plasma<\/a> \u2014 which contains many dissolved substances, and cells, including erythrocytes<\/a>, leukocytes<\/a> and thrombocytes<\/a>.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n14.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the heart and how it functions.<\/li>\n
- Compare and contrast the pulmonary and systemic circulations.<\/li>\n
- \n\n
Two Circulations<\/h1>\r\n<\/div>\r\nCells throughout the body need a constant supply of oxygen. They get oxygen from capillaries in the systemic circulation. The systemic circulation is just one of two interconnected circulations that make up the human cardiovascular system. The other circulation is the pulmonary system, which is where blood picks up oxygen to carry to cells. It takes blood about 20 seconds to make one complete transit through both circulations (see Figure 14.2.5).\r\n\r\n[caption id=\"attachment_4389\" align=\"aligncenter\" width=\"927\"] Figure 14.2.5 There are two main circuits through which blood flows in the cardiovascular system. In the pulmonary circuit, blood moves from the right side of the heart to the lungs and then back to the left side of the heart. In the systemic circuit, blood moves from the left side of the heart to the body tissues and then back to the right side of the heart.<\/em>[\/caption]\r\nPulmonary Circuit<\/h2>\r\nThe\u00a0[pb_glossary id=\"4387\"]pulmonary<\/strong>\u00a0<\/strong>circuit<\/strong>[\/pb_glossary] involves only the heart, the lungs, and the major blood vessels that connect them (illustrated in Figure 14.2.6). Blood moves through the pulmonary circuit from the heart, to the lungs, and then back to the heart again, becoming oxygenated in the process. Specifically, the right ventricle of the heart pumps deoxygenated blood into the right and left pulmonary arteries. These arteries carry the blood to the right and left lungs, respectively. Oxygenated blood then returns from the right and left lungs through the two right and two left pulmonary veins. All four pulmonary veins enter the left atrium of the heart.\r\n\r\n[caption id=\"attachment_4391\" align=\"aligncenter\" width=\"520\"] Figure 14.2.6 This diagram shows the heart, lungs, and major vessels that make up the pulmonary circulation. The coloured arrows indicate the direction of blood flow \u2014 red for oxygenated blood and blue for relatively deoxygenated blood.<\/em>[\/caption]\r\n\r\nWhat happens to the blood while it is in the lungs? It passes through increasingly smaller arteries, and finally through capillary networks surrounding the alveoli (see Figure 14.2.7). This is where gas exchange takes place. The deoxygenated blood in the capillaries picks up oxygen from the alveoli, and gives up carbon dioxide to the alveoli. As a result, the blood returning to the heart in the pulmonary veins is almost completely saturated with oxygen.\r\n\r\n[caption id=\"attachment_4392\" align=\"aligncenter\" width=\"812\"] Figure 14.2.7 This diagram illustrates clusters of alveoli in the lungs, where gas exchange takes place with blood in capillaries as it passes through the pulmonary circulation.<\/em>[\/caption]\r\nSystemic Circulation<\/h2>\r\nThe oxygenated blood that enters the left atrium of the heart in the pulmonary circulation then passes into the\u00a0[pb_glossary id=\"4393\"]systemic circuit[\/pb_glossary].<\/strong>\u00a0This is the part of the cardiovascular system that transports blood to and from all of the tissues of the body to provide oxygen and\u00a0nutrients, and to pick up wastes. It consists of the heart and blood vessels that supply the metabolic needs of all the cells in the body, including those of the heart and lungs.\r\n\r\nAs shown in Figure 14.2.8, in the systemic circulation, the left atrium pumps oxygenated blood to the left ventricle, which pumps the blood directly into the aorta, the body\u2019s largest artery. Major arteries branching off the aorta carry the blood to the head and upper extremities. The aorta continues down through the abdomen and carries blood to the abdomen and lower extremities. The blood then returns to the heart through the network of increasingly larger veins of the systemic circulation. All of the returning blood eventually collects in the superior vena cava (upper body) and inferior vena cava (lower body), which empty directly into the right atrium of the heart.\r\n\r\n[caption id=\"attachment_4394\" align=\"aligncenter\" width=\"566\"] Figure 14.2.8 The systemic circulation includes the aorta (red), which carries oxygenated blood away from the heart to the rest of the body; and the inferior and superior venae cavae (blue), which return deoxygenated blood to the heart from the body. The coloured arrows in the diagram indicate the direction of blood flow \u2014 red for oxygenated and blue for deoxygenated.<\/em>[\/caption]\r\nBlood<\/h2>\r\n[caption id=\"attachment_4396\" align=\"alignright\" width=\"500\"] Figure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em>[\/caption]\r\n\r\n[pb_glossary id=\"2702\"]Blood[\/pb_glossary]<\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0[pb_glossary id=\"4330\"]pH[\/pb_glossary], among other functions.\r\n\r\nThe fluid part of blood is called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary]<\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.\r\n\r\n \t- [pb_glossary id=\"4398\"]Erythrocytes[\/pb_glossary] <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0[pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary]<\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\r\n \t
- [pb_glossary id=\"5623\"]Leukocytes[\/pb_glossary] <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\r\n \t
- [pb_glossary id=\"4399\"]Thrombocytes[\/pb_glossary]<\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\r\n<\/ul>\r\n\r\n
\r\n14.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5927\"]cardiovascular system[\/pb_glossary] is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the [pb_glossary id=\"2987\"]heart[\/pb_glossary], [pb_glossary id=\"5835\"]blood vessels[\/pb_glossary], and [pb_glossary id=\"2702\"]blood[\/pb_glossary].<\/li>\r\n \t
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\r\n \t
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\r\n \t
- The cardiovascular system has two interconnected circulations. The [pb_glossary id=\"4387\"]pulmonary circuit[\/pb_glossary] carries blood between the heart and lungs, where blood is oxygenated. The [pb_glossary id=\"4393\"]systemic circuit[\/pb_glossary] carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\r\n \t
- Blood is a [pb_glossary id=\"4402\"]fluid connective tissue[\/pb_glossary] that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary] \u2014 which contains many dissolved substances, and cells, including [pb_glossary id=\"4398\"]erythrocytes[\/pb_glossary], [pb_glossary id=\"5623\"]leukocytes[\/pb_glossary] and [pb_glossary id=\"4399\"]thrombocytes[\/pb_glossary].<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n14.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the heart and how it functions.<\/li>\r\n \t
- Compare and contrast the pulmonary and systemic circulations.<\/li>\r\n \t
- [h5p id=\"612\"]<\/li>\r\n \t
- What is blood? What are its chief constituents?<\/li>\r\n \t
- Name three different types of substances transported by the cardiovascular system.<\/li>\r\n \t
- Explain why the heart and lungs need blood from the systemic circulation.<\/li>\r\n \t
- Do blood vessels carrying deoxygenated blood from the body back to the heart get increasingly larger or smaller?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n14.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=emb_logo\r\nHow the heart actually pumps blood - Edmond Hui, TED-Ed, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=emb_logo\r\n
Circulatory & Respiratory Systems - CrashCourse Biology #27, CrashCourse, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU\r\n
The Heart and Circulatory System - How They Work, Mayo Clinic, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 14.2.1<\/strong>\r\n\r\nBrain vascular formation<\/a> [photo] by Liulin Du\/ Chen (The National Cancer Institute at Frederick) on PLOS Biology<\/a> is used under a CC BY 4.0<\/a> license.\r\n\r\nFigure 14.2.2<\/strong>\r\n\r\nCirculatory_System_no_tags.svg<\/a> by Mariana Ruiz Villarreal [LadyofHats]<\/a> on Wikimedia Commons is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.3<\/strong>\r\n\r\nBlausen_0462_HeartAnatomy<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0)\r\n\r\nFigure 14.2.4<\/strong>\r\n\r\nStructure and functions of the different types of blood vessels<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\r\nFigure 14.2.5<\/strong>\r\n\r\n2101_Blood_Flow_Through_the_Heart<\/a>\u00a0by OpenStax College<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.6<\/strong>\r\n\r\nIllu_pulmonary_circuit<\/a> by Arcadian<\/a> from National Cancer Institute\/ SEER Training<\/a> on Wikimedia Commons is in the the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.7<\/strong>\r\n\r\nPulmonary_Blood_Circulation<\/a> by Artwork by Holly Fischer from Open Michigan (Respiratory Tact Slide 20)<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.8<\/strong>\r\n\r\nsystemic_circuit.svg<\/a> by Surachit<\/a> on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/) license. (Derivative work based on SEER Training by NCI\/ U.S. Government<\/a>).\r\n\r\nFigure 14.2.9<\/strong>\r\n\r\nRed_White_Blood_cells<\/a> by Electron Microscopy Facility at The National Cancer Institute at Frederick (NCI-Frederick) on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\nReferences<\/h2>\r\n
Blausen.com Staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine<\/i>\u00a01<\/b>\u00a0(2).\u00a0DOI:10.15347\/wjm\/2014.010.\u00a0ISSN\u00a02002-4436<\/p>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 20.2 Cardiovascular circulation [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 7.3). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/20-1-structure-and-function-of-blood-vessels<\/p>\r\nBrainard, J\/ CK-12 Foundation. (2016). Figure 4 Diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system [digital image]. In CK-12 College Human Biology<\/em> (Section 16.2) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/16.2\/<\/p>\r\nCrashCourse. (2012, July 30). Circulatory & respiratory systems - CrashCourse Biology #27. YouTube. https:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=youtu.be<\/p>\r\n
Du, J. (2012, August). Brain vasculature formation [digital image]. PLoS Biology,<\/em> 10(8): ev10.i08. https:\/\/doi.org\/10.1371\/image.pbio.v10.i08 \u00a9 Chen.<\/p>\r\nMayo Clinic. (2013). The heart and circulatory system - How they work. YouTube. https:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU&t=1s<\/p>\r\n
TED-Ed. (2014, May 20). How the heart actually pumps blood - Edmond Hui. YouTube. https:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\nFigure 14.2.1 What are these strange tunnels?<\/em><\/figcaption><\/figure>\n\nAnt Hill or Plumbing System?<\/h1>\n<\/div>\n
What do you think the picture in Figure 14.2.1 shows? Is it a maze of underground passageways in an ant hill? A network of interconnected pipes in a complex plumbing system? The picture actually shows something that, like ant tunnels and plumbing pipes, functions as a transportation system. It shows a network of blood vessels, which are part of the cardiovascular system.<\/p>\n
\nWhat is the Cardiovascular System?<\/h1>\n<\/div>\n
The\u00a0cardiovascular system<\/a><\/strong>, also called the circulatory system, is the organ system that transports materials to and from all the cells of the body. The materials carried by the cardiovascular system include oxygen from the lungs<\/a>, nutrients from the digestive system<\/a>, hormones<\/a> from glands of the endocrine system<\/a>, and waste materials from cells throughout the body. Transport of these and many other materials is necessary to maintain homeostasis<\/a> of the body. The main components of the cardiovascular system are the heart, blood vessels, and blood. Each of these components is shown in Figure 14.2.2 and introduced below.<\/p>\nFigure 14.2.2 This simplified drawing of the cardiovascular system shows its main structures. The heart is shown in the chest in red. Blood vessels called arteries are also shown in red, and blood vessels called veins are shown in blue.<\/em><\/figcaption><\/figure>\n\nHeart<\/h1>\n<\/div>\n
The\u00a0heart<\/a><\/strong> is a muscular organ in the chest. It consists mainly of cardiac muscle<\/a> tissue, and it pumps blood through blood vessels by repeated, rhythmic contractions. As shown in Figure 14.2.3, the heart has four inner chambers: a right atrium and ventricle, and a left atrium and ventricle. On each side of the heart, blood is pumped from the atrium to the ventricle below it, and from the ventricle out of the heart. The heart also contains several valves that allow blood to flow only in the proper direction through the heart.<\/p>\nFigure 14.2.3 The right side of the heart includes the right atrium and right ventricle. The left side includes the left atrium and left ventricle.<\/em><\/figcaption><\/figure>\n <\/p>\n
As you may have noticed, the Figure 14.2.3 diagram labels the right side of the heart on the left side of the diagram, and vice versa.\u00a0 This is because it is assumed that in this diagram, the heart appears\u00a0 as if the patient was facing us – the patient’s left side is on our right side!<\/p>\n
Unlike skeletal muscle, cardiac muscle routinely contracts without stimulation by the\u00a0nervous system. Specialized cardiac muscle\u00a0cells\u00a0send out electrical impulses that stimulate the contractions. As a result, the atria and ventricles normally contract with just the right timing to keep blood pumping efficiently through the heart.<\/p>\n
\nBlood Vessels<\/h1>\n<\/div>\n
The blood vessels<\/a> of the cardiovascular system are like a network of interconnected, one-way roads that range from superhighways to back alleys. Like a network of roads, the blood vessels are tasked with allowing the transport of materials from one place to another. There are three major types of blood vessels: arteries, veins, and capillaries. They are illustrated in Figure 14.2.4 and described below.<\/p>\nFigure 14.2.4 This diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system.<\/em><\/figcaption><\/figure>\n\n- Arteries<\/a><\/strong>\u00a0are blood vessels that carry blood away from the heart (except for the arteries that actually supply blood to the heart muscle). Most arteries carry oxygen-rich blood, and one of their main functions is distributing oxygen to tissues throughout the body. The smallest arteries are called arterioles.<\/li>\n
- Veins<\/a><\/strong>\u00a0are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood. The smallest veins are called venules.<\/li>\n
- Capillaries<\/a><\/strong>\u00a0are the smallest blood vessels, and they connect arterioles and venules. As they pass through tissues, they exchange substances (including oxygen) with\u00a0cells.<\/li>\n<\/ul>\n\n
Two Circulations<\/h1>\n<\/div>\n
Cells throughout the body need a constant supply of oxygen. They get oxygen from capillaries in the systemic circulation. The systemic circulation is just one of two interconnected circulations that make up the human cardiovascular system. The other circulation is the pulmonary system, which is where blood picks up oxygen to carry to cells. It takes blood about 20 seconds to make one complete transit through both circulations (see Figure 14.2.5).<\/p>\nFigure 14.2.5 There are two main circuits through which blood flows in the cardiovascular system. In the pulmonary circuit, blood moves from the right side of the heart to the lungs and then back to the left side of the heart. In the systemic circuit, blood moves from the left side of the heart to the body tissues and then back to the right side of the heart.<\/em><\/figcaption><\/figure>\nPulmonary Circuit<\/h2>\n
The\u00a0pulmonary<\/strong>\u00a0<\/strong>circuit<\/strong><\/a> involves only the heart, the lungs, and the major blood vessels that connect them (illustrated in Figure 14.2.6). Blood moves through the pulmonary circuit from the heart, to the lungs, and then back to the heart again, becoming oxygenated in the process. Specifically, the right ventricle of the heart pumps deoxygenated blood into the right and left pulmonary arteries. These arteries carry the blood to the right and left lungs, respectively. Oxygenated blood then returns from the right and left lungs through the two right and two left pulmonary veins. All four pulmonary veins enter the left atrium of the heart.<\/p>\nFigure 14.2.6 This diagram shows the heart, lungs, and major vessels that make up the pulmonary circulation. The coloured arrows indicate the direction of blood flow \u2014 red for oxygenated blood and blue for relatively deoxygenated blood.<\/em><\/figcaption><\/figure>\nWhat happens to the blood while it is in the lungs? It passes through increasingly smaller arteries, and finally through capillary networks surrounding the alveoli (see Figure 14.2.7). This is where gas exchange takes place. The deoxygenated blood in the capillaries picks up oxygen from the alveoli, and gives up carbon dioxide to the alveoli. As a result, the blood returning to the heart in the pulmonary veins is almost completely saturated with oxygen.<\/p>\nFigure 14.2.7 This diagram illustrates clusters of alveoli in the lungs, where gas exchange takes place with blood in capillaries as it passes through the pulmonary circulation.<\/em><\/figcaption><\/figure>\nSystemic Circulation<\/h2>\n
The oxygenated blood that enters the left atrium of the heart in the pulmonary circulation then passes into the\u00a0systemic circuit<\/a>.<\/strong>\u00a0This is the part of the cardiovascular system that transports blood to and from all of the tissues of the body to provide oxygen and\u00a0nutrients, and to pick up wastes. It consists of the heart and blood vessels that supply the metabolic needs of all the cells in the body, including those of the heart and lungs.<\/p>\nAs shown in Figure 14.2.8, in the systemic circulation, the left atrium pumps oxygenated blood to the left ventricle, which pumps the blood directly into the aorta, the body\u2019s largest artery. Major arteries branching off the aorta carry the blood to the head and upper extremities. The aorta continues down through the abdomen and carries blood to the abdomen and lower extremities. The blood then returns to the heart through the network of increasingly larger veins of the systemic circulation. All of the returning blood eventually collects in the superior vena cava (upper body) and inferior vena cava (lower body), which empty directly into the right atrium of the heart.<\/p>\nFigure 14.2.8 The systemic circulation includes the aorta (red), which carries oxygenated blood away from the heart to the rest of the body; and the inferior and superior venae cavae (blue), which return deoxygenated blood to the heart from the body. The coloured arrows in the diagram indicate the direction of blood flow \u2014 red for oxygenated and blue for deoxygenated.<\/em><\/figcaption><\/figure>\nBlood<\/h2>\nFigure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em><\/figcaption><\/figure>\nBlood<\/a><\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0pH<\/a>, among other functions.<\/p>\nThe fluid part of blood is called\u00a0plasma<\/a><\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.<\/p>\n\n- Erythrocytes<\/a> <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0hemoglobin<\/a><\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\n
- Leukocytes<\/a> <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\n
- Thrombocytes<\/a><\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\n<\/ul>\n\n\n
\n14.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- The cardiovascular system<\/a> is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the heart<\/a>, blood vessels<\/a>, and blood<\/a>.<\/li>\n
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\n
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\n
- The cardiovascular system has two interconnected circulations. The pulmonary circuit<\/a> carries blood between the heart and lungs, where blood is oxygenated. The systemic circuit<\/a> carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\n
- Blood is a fluid connective tissue<\/a> that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0plasma<\/a> \u2014 which contains many dissolved substances, and cells, including erythrocytes<\/a>, leukocytes<\/a> and thrombocytes<\/a>.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n14.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the heart and how it functions.<\/li>\n
- Compare and contrast the pulmonary and systemic circulations.<\/li>\n
- \n\n
Figure 14.2.6 This diagram shows the heart, lungs, and major vessels that make up the pulmonary circulation. The coloured arrows indicate the direction of blood flow \u2014 red for oxygenated blood and blue for relatively deoxygenated blood.<\/em>[\/caption]\r\n\r\nWhat happens to the blood while it is in the lungs? It passes through increasingly smaller arteries, and finally through capillary networks surrounding the alveoli (see Figure 14.2.7). This is where gas exchange takes place. The deoxygenated blood in the capillaries picks up oxygen from the alveoli, and gives up carbon dioxide to the alveoli. As a result, the blood returning to the heart in the pulmonary veins is almost completely saturated with oxygen.\r\n\r\n[caption id=\"attachment_4392\" align=\"aligncenter\" width=\"812\"] Figure 14.2.7 This diagram illustrates clusters of alveoli in the lungs, where gas exchange takes place with blood in capillaries as it passes through the pulmonary circulation.<\/em>[\/caption]\r\nSystemic Circulation<\/h2>\r\nThe oxygenated blood that enters the left atrium of the heart in the pulmonary circulation then passes into the\u00a0[pb_glossary id=\"4393\"]systemic circuit[\/pb_glossary].<\/strong>\u00a0This is the part of the cardiovascular system that transports blood to and from all of the tissues of the body to provide oxygen and\u00a0nutrients, and to pick up wastes. It consists of the heart and blood vessels that supply the metabolic needs of all the cells in the body, including those of the heart and lungs.\r\n\r\nAs shown in Figure 14.2.8, in the systemic circulation, the left atrium pumps oxygenated blood to the left ventricle, which pumps the blood directly into the aorta, the body\u2019s largest artery. Major arteries branching off the aorta carry the blood to the head and upper extremities. The aorta continues down through the abdomen and carries blood to the abdomen and lower extremities. The blood then returns to the heart through the network of increasingly larger veins of the systemic circulation. All of the returning blood eventually collects in the superior vena cava (upper body) and inferior vena cava (lower body), which empty directly into the right atrium of the heart.\r\n\r\n[caption id=\"attachment_4394\" align=\"aligncenter\" width=\"566\"] Figure 14.2.8 The systemic circulation includes the aorta (red), which carries oxygenated blood away from the heart to the rest of the body; and the inferior and superior venae cavae (blue), which return deoxygenated blood to the heart from the body. The coloured arrows in the diagram indicate the direction of blood flow \u2014 red for oxygenated and blue for deoxygenated.<\/em>[\/caption]\r\nBlood<\/h2>\r\n[caption id=\"attachment_4396\" align=\"alignright\" width=\"500\"] Figure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em>[\/caption]\r\n\r\n[pb_glossary id=\"2702\"]Blood[\/pb_glossary]<\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0[pb_glossary id=\"4330\"]pH[\/pb_glossary], among other functions.\r\n\r\nThe fluid part of blood is called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary]<\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.\r\n\r\n \t- [pb_glossary id=\"4398\"]Erythrocytes[\/pb_glossary] <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0[pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary]<\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\r\n \t
- [pb_glossary id=\"5623\"]Leukocytes[\/pb_glossary] <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\r\n \t
- [pb_glossary id=\"4399\"]Thrombocytes[\/pb_glossary]<\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\r\n<\/ul>\r\n\r\n
\r\n14.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5927\"]cardiovascular system[\/pb_glossary] is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the [pb_glossary id=\"2987\"]heart[\/pb_glossary], [pb_glossary id=\"5835\"]blood vessels[\/pb_glossary], and [pb_glossary id=\"2702\"]blood[\/pb_glossary].<\/li>\r\n \t
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\r\n \t
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\r\n \t
- The cardiovascular system has two interconnected circulations. The [pb_glossary id=\"4387\"]pulmonary circuit[\/pb_glossary] carries blood between the heart and lungs, where blood is oxygenated. The [pb_glossary id=\"4393\"]systemic circuit[\/pb_glossary] carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\r\n \t
- Blood is a [pb_glossary id=\"4402\"]fluid connective tissue[\/pb_glossary] that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary] \u2014 which contains many dissolved substances, and cells, including [pb_glossary id=\"4398\"]erythrocytes[\/pb_glossary], [pb_glossary id=\"5623\"]leukocytes[\/pb_glossary] and [pb_glossary id=\"4399\"]thrombocytes[\/pb_glossary].<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n14.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the heart and how it functions.<\/li>\r\n \t
- Compare and contrast the pulmonary and systemic circulations.<\/li>\r\n \t
- [h5p id=\"612\"]<\/li>\r\n \t
- What is blood? What are its chief constituents?<\/li>\r\n \t
- Name three different types of substances transported by the cardiovascular system.<\/li>\r\n \t
- Explain why the heart and lungs need blood from the systemic circulation.<\/li>\r\n \t
- Do blood vessels carrying deoxygenated blood from the body back to the heart get increasingly larger or smaller?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n14.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=emb_logo\r\nHow the heart actually pumps blood - Edmond Hui, TED-Ed, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=emb_logo\r\n
Circulatory & Respiratory Systems - CrashCourse Biology #27, CrashCourse, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU\r\n
The Heart and Circulatory System - How They Work, Mayo Clinic, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 14.2.1<\/strong>\r\n\r\nBrain vascular formation<\/a> [photo] by Liulin Du\/ Chen (The National Cancer Institute at Frederick) on PLOS Biology<\/a> is used under a CC BY 4.0<\/a> license.\r\n\r\nFigure 14.2.2<\/strong>\r\n\r\nCirculatory_System_no_tags.svg<\/a> by Mariana Ruiz Villarreal [LadyofHats]<\/a> on Wikimedia Commons is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.3<\/strong>\r\n\r\nBlausen_0462_HeartAnatomy<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0)\r\n\r\nFigure 14.2.4<\/strong>\r\n\r\nStructure and functions of the different types of blood vessels<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\r\nFigure 14.2.5<\/strong>\r\n\r\n2101_Blood_Flow_Through_the_Heart<\/a>\u00a0by OpenStax College<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.6<\/strong>\r\n\r\nIllu_pulmonary_circuit<\/a> by Arcadian<\/a> from National Cancer Institute\/ SEER Training<\/a> on Wikimedia Commons is in the the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.7<\/strong>\r\n\r\nPulmonary_Blood_Circulation<\/a> by Artwork by Holly Fischer from Open Michigan (Respiratory Tact Slide 20)<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.8<\/strong>\r\n\r\nsystemic_circuit.svg<\/a> by Surachit<\/a> on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/) license. (Derivative work based on SEER Training by NCI\/ U.S. Government<\/a>).\r\n\r\nFigure 14.2.9<\/strong>\r\n\r\nRed_White_Blood_cells<\/a> by Electron Microscopy Facility at The National Cancer Institute at Frederick (NCI-Frederick) on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\nReferences<\/h2>\r\n
Blausen.com Staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine<\/i>\u00a01<\/b>\u00a0(2).\u00a0DOI:10.15347\/wjm\/2014.010.\u00a0ISSN\u00a02002-4436<\/p>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 20.2 Cardiovascular circulation [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 7.3). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/20-1-structure-and-function-of-blood-vessels<\/p>\r\nBrainard, J\/ CK-12 Foundation. (2016). Figure 4 Diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system [digital image]. In CK-12 College Human Biology<\/em> (Section 16.2) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/16.2\/<\/p>\r\nCrashCourse. (2012, July 30). Circulatory & respiratory systems - CrashCourse Biology #27. YouTube. https:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=youtu.be<\/p>\r\n
Du, J. (2012, August). Brain vasculature formation [digital image]. PLoS Biology,<\/em> 10(8): ev10.i08. https:\/\/doi.org\/10.1371\/image.pbio.v10.i08 \u00a9 Chen.<\/p>\r\nMayo Clinic. (2013). The heart and circulatory system - How they work. YouTube. https:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU&t=1s<\/p>\r\n
TED-Ed. (2014, May 20). How the heart actually pumps blood - Edmond Hui. YouTube. https:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\nFigure 14.2.1 What are these strange tunnels?<\/em><\/figcaption><\/figure>\n\nAnt Hill or Plumbing System?<\/h1>\n<\/div>\n
What do you think the picture in Figure 14.2.1 shows? Is it a maze of underground passageways in an ant hill? A network of interconnected pipes in a complex plumbing system? The picture actually shows something that, like ant tunnels and plumbing pipes, functions as a transportation system. It shows a network of blood vessels, which are part of the cardiovascular system.<\/p>\n
\nWhat is the Cardiovascular System?<\/h1>\n<\/div>\n
The\u00a0cardiovascular system<\/a><\/strong>, also called the circulatory system, is the organ system that transports materials to and from all the cells of the body. The materials carried by the cardiovascular system include oxygen from the lungs<\/a>, nutrients from the digestive system<\/a>, hormones<\/a> from glands of the endocrine system<\/a>, and waste materials from cells throughout the body. Transport of these and many other materials is necessary to maintain homeostasis<\/a> of the body. The main components of the cardiovascular system are the heart, blood vessels, and blood. Each of these components is shown in Figure 14.2.2 and introduced below.<\/p>\nFigure 14.2.2 This simplified drawing of the cardiovascular system shows its main structures. The heart is shown in the chest in red. Blood vessels called arteries are also shown in red, and blood vessels called veins are shown in blue.<\/em><\/figcaption><\/figure>\n\nHeart<\/h1>\n<\/div>\n
The\u00a0heart<\/a><\/strong> is a muscular organ in the chest. It consists mainly of cardiac muscle<\/a> tissue, and it pumps blood through blood vessels by repeated, rhythmic contractions. As shown in Figure 14.2.3, the heart has four inner chambers: a right atrium and ventricle, and a left atrium and ventricle. On each side of the heart, blood is pumped from the atrium to the ventricle below it, and from the ventricle out of the heart. The heart also contains several valves that allow blood to flow only in the proper direction through the heart.<\/p>\nFigure 14.2.3 The right side of the heart includes the right atrium and right ventricle. The left side includes the left atrium and left ventricle.<\/em><\/figcaption><\/figure>\n <\/p>\n
As you may have noticed, the Figure 14.2.3 diagram labels the right side of the heart on the left side of the diagram, and vice versa.\u00a0 This is because it is assumed that in this diagram, the heart appears\u00a0 as if the patient was facing us – the patient’s left side is on our right side!<\/p>\n
Unlike skeletal muscle, cardiac muscle routinely contracts without stimulation by the\u00a0nervous system. Specialized cardiac muscle\u00a0cells\u00a0send out electrical impulses that stimulate the contractions. As a result, the atria and ventricles normally contract with just the right timing to keep blood pumping efficiently through the heart.<\/p>\n
\nBlood Vessels<\/h1>\n<\/div>\n
The blood vessels<\/a> of the cardiovascular system are like a network of interconnected, one-way roads that range from superhighways to back alleys. Like a network of roads, the blood vessels are tasked with allowing the transport of materials from one place to another. There are three major types of blood vessels: arteries, veins, and capillaries. They are illustrated in Figure 14.2.4 and described below.<\/p>\nFigure 14.2.4 This diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system.<\/em><\/figcaption><\/figure>\n\n- Arteries<\/a><\/strong>\u00a0are blood vessels that carry blood away from the heart (except for the arteries that actually supply blood to the heart muscle). Most arteries carry oxygen-rich blood, and one of their main functions is distributing oxygen to tissues throughout the body. The smallest arteries are called arterioles.<\/li>\n
- Veins<\/a><\/strong>\u00a0are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood. The smallest veins are called venules.<\/li>\n
- Capillaries<\/a><\/strong>\u00a0are the smallest blood vessels, and they connect arterioles and venules. As they pass through tissues, they exchange substances (including oxygen) with\u00a0cells.<\/li>\n<\/ul>\n\n
Two Circulations<\/h1>\n<\/div>\n
Cells throughout the body need a constant supply of oxygen. They get oxygen from capillaries in the systemic circulation. The systemic circulation is just one of two interconnected circulations that make up the human cardiovascular system. The other circulation is the pulmonary system, which is where blood picks up oxygen to carry to cells. It takes blood about 20 seconds to make one complete transit through both circulations (see Figure 14.2.5).<\/p>\nFigure 14.2.5 There are two main circuits through which blood flows in the cardiovascular system. In the pulmonary circuit, blood moves from the right side of the heart to the lungs and then back to the left side of the heart. In the systemic circuit, blood moves from the left side of the heart to the body tissues and then back to the right side of the heart.<\/em><\/figcaption><\/figure>\nPulmonary Circuit<\/h2>\n
The\u00a0pulmonary<\/strong>\u00a0<\/strong>circuit<\/strong><\/a> involves only the heart, the lungs, and the major blood vessels that connect them (illustrated in Figure 14.2.6). Blood moves through the pulmonary circuit from the heart, to the lungs, and then back to the heart again, becoming oxygenated in the process. Specifically, the right ventricle of the heart pumps deoxygenated blood into the right and left pulmonary arteries. These arteries carry the blood to the right and left lungs, respectively. Oxygenated blood then returns from the right and left lungs through the two right and two left pulmonary veins. All four pulmonary veins enter the left atrium of the heart.<\/p>\nFigure 14.2.6 This diagram shows the heart, lungs, and major vessels that make up the pulmonary circulation. The coloured arrows indicate the direction of blood flow \u2014 red for oxygenated blood and blue for relatively deoxygenated blood.<\/em><\/figcaption><\/figure>\nWhat happens to the blood while it is in the lungs? It passes through increasingly smaller arteries, and finally through capillary networks surrounding the alveoli (see Figure 14.2.7). This is where gas exchange takes place. The deoxygenated blood in the capillaries picks up oxygen from the alveoli, and gives up carbon dioxide to the alveoli. As a result, the blood returning to the heart in the pulmonary veins is almost completely saturated with oxygen.<\/p>\nFigure 14.2.7 This diagram illustrates clusters of alveoli in the lungs, where gas exchange takes place with blood in capillaries as it passes through the pulmonary circulation.<\/em><\/figcaption><\/figure>\nSystemic Circulation<\/h2>\n
The oxygenated blood that enters the left atrium of the heart in the pulmonary circulation then passes into the\u00a0systemic circuit<\/a>.<\/strong>\u00a0This is the part of the cardiovascular system that transports blood to and from all of the tissues of the body to provide oxygen and\u00a0nutrients, and to pick up wastes. It consists of the heart and blood vessels that supply the metabolic needs of all the cells in the body, including those of the heart and lungs.<\/p>\nAs shown in Figure 14.2.8, in the systemic circulation, the left atrium pumps oxygenated blood to the left ventricle, which pumps the blood directly into the aorta, the body\u2019s largest artery. Major arteries branching off the aorta carry the blood to the head and upper extremities. The aorta continues down through the abdomen and carries blood to the abdomen and lower extremities. The blood then returns to the heart through the network of increasingly larger veins of the systemic circulation. All of the returning blood eventually collects in the superior vena cava (upper body) and inferior vena cava (lower body), which empty directly into the right atrium of the heart.<\/p>\nFigure 14.2.8 The systemic circulation includes the aorta (red), which carries oxygenated blood away from the heart to the rest of the body; and the inferior and superior venae cavae (blue), which return deoxygenated blood to the heart from the body. The coloured arrows in the diagram indicate the direction of blood flow \u2014 red for oxygenated and blue for deoxygenated.<\/em><\/figcaption><\/figure>\nBlood<\/h2>\nFigure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em><\/figcaption><\/figure>\nBlood<\/a><\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0pH<\/a>, among other functions.<\/p>\nThe fluid part of blood is called\u00a0plasma<\/a><\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.<\/p>\n\n- Erythrocytes<\/a> <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0hemoglobin<\/a><\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\n
- Leukocytes<\/a> <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\n
- Thrombocytes<\/a><\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\n<\/ul>\n\n\n
\n14.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- The cardiovascular system<\/a> is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the heart<\/a>, blood vessels<\/a>, and blood<\/a>.<\/li>\n
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\n
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\n
- The cardiovascular system has two interconnected circulations. The pulmonary circuit<\/a> carries blood between the heart and lungs, where blood is oxygenated. The systemic circuit<\/a> carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\n
- Blood is a fluid connective tissue<\/a> that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0plasma<\/a> \u2014 which contains many dissolved substances, and cells, including erythrocytes<\/a>, leukocytes<\/a> and thrombocytes<\/a>.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n14.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the heart and how it functions.<\/li>\n
- Compare and contrast the pulmonary and systemic circulations.<\/li>\n
- \n\n
Figure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em>[\/caption]\r\n\r\n[pb_glossary id=\"2702\"]Blood[\/pb_glossary]<\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0[pb_glossary id=\"4330\"]pH[\/pb_glossary], among other functions.\r\n\r\nThe fluid part of blood is called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary]<\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.\r\n- \r\n \t
- [pb_glossary id=\"4398\"]Erythrocytes[\/pb_glossary] <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0[pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary]<\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\r\n \t
- [pb_glossary id=\"5623\"]Leukocytes[\/pb_glossary] <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\r\n \t
- [pb_glossary id=\"4399\"]Thrombocytes[\/pb_glossary]<\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\r\n<\/ul>\r\n
\r\n\r\n 14.2 Summary<\/span><\/h1>\r\n<\/header>\r\n
\r\n- \r\n \t
- The [pb_glossary id=\"5927\"]cardiovascular system[\/pb_glossary] is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the [pb_glossary id=\"2987\"]heart[\/pb_glossary], [pb_glossary id=\"5835\"]blood vessels[\/pb_glossary], and [pb_glossary id=\"2702\"]blood[\/pb_glossary].<\/li>\r\n \t
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\r\n \t
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\r\n \t
- The cardiovascular system has two interconnected circulations. The [pb_glossary id=\"4387\"]pulmonary circuit[\/pb_glossary] carries blood between the heart and lungs, where blood is oxygenated. The [pb_glossary id=\"4393\"]systemic circuit[\/pb_glossary] carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\r\n \t
- Blood is a [pb_glossary id=\"4402\"]fluid connective tissue[\/pb_glossary] that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0[pb_glossary id=\"4395\"]plasma[\/pb_glossary] \u2014 which contains many dissolved substances, and cells, including [pb_glossary id=\"4398\"]erythrocytes[\/pb_glossary], [pb_glossary id=\"5623\"]leukocytes[\/pb_glossary] and [pb_glossary id=\"4399\"]thrombocytes[\/pb_glossary].<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n 14.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n
\r\n- \r\n \t
- Describe the heart and how it functions.<\/li>\r\n \t
- Compare and contrast the pulmonary and systemic circulations.<\/li>\r\n \t
- [h5p id=\"612\"]<\/li>\r\n \t
- What is blood? What are its chief constituents?<\/li>\r\n \t
- Name three different types of substances transported by the cardiovascular system.<\/li>\r\n \t
- Explain why the heart and lungs need blood from the systemic circulation.<\/li>\r\n \t
- Do blood vessels carrying deoxygenated blood from the body back to the heart get increasingly larger or smaller?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n 14.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n
\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=emb_logo\r\nHow the heart actually pumps blood - Edmond Hui, TED-Ed, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=emb_logo\r\n
Circulatory & Respiratory Systems - CrashCourse Biology #27, CrashCourse, 2012.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU\r\n
The Heart and Circulatory System - How They Work, Mayo Clinic, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 14.2.1<\/strong>\r\n\r\nBrain vascular formation<\/a> [photo] by Liulin Du\/ Chen (The National Cancer Institute at Frederick) on PLOS Biology<\/a> is used under a CC BY 4.0<\/a> license.\r\n\r\nFigure 14.2.2<\/strong>\r\n\r\nCirculatory_System_no_tags.svg<\/a> by Mariana Ruiz Villarreal [LadyofHats]<\/a> on Wikimedia Commons is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.3<\/strong>\r\n\r\nBlausen_0462_HeartAnatomy<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0)\r\n\r\nFigure 14.2.4<\/strong>\r\n\r\nStructure and functions of the different types of blood vessels<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n
\u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\r\nFigure 14.2.5<\/strong>\r\n\r\n2101_Blood_Flow_Through_the_Heart<\/a>\u00a0by OpenStax College<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.6<\/strong>\r\n\r\nIllu_pulmonary_circuit<\/a> by Arcadian<\/a> from National Cancer Institute\/ SEER Training<\/a> on Wikimedia Commons is in the the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 14.2.7<\/strong>\r\n\r\nPulmonary_Blood_Circulation<\/a> by Artwork by Holly Fischer from Open Michigan (Respiratory Tact Slide 20)<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 14.2.8<\/strong>\r\n\r\nsystemic_circuit.svg<\/a> by Surachit<\/a> on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (http:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/) license. (Derivative work based on SEER Training by NCI\/ U.S. Government<\/a>).\r\n\r\nFigure 14.2.9<\/strong>\r\n\r\nRed_White_Blood_cells<\/a> by Electron Microscopy Facility at The National Cancer Institute at Frederick (NCI-Frederick) on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\nReferences<\/h2>\r\n
Blausen.com Staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine<\/i>\u00a01<\/b>\u00a0(2).\u00a0DOI:10.15347\/wjm\/2014.010.\u00a0ISSN\u00a02002-4436<\/p>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 20.2 Cardiovascular circulation [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 7.3). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/20-1-structure-and-function-of-blood-vessels<\/p>\r\n
Brainard, J\/ CK-12 Foundation. (2016). Figure 4 Diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system [digital image]. In CK-12 College Human Biology<\/em> (Section 16.2) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/16.2\/<\/p>\r\n
CrashCourse. (2012, July 30). Circulatory & respiratory systems - CrashCourse Biology #27. YouTube. https:\/\/www.youtube.com\/watch?v=9fxm85Fy4sQ&feature=youtu.be<\/p>\r\n
Du, J. (2012, August). Brain vasculature formation [digital image]. PLoS Biology,<\/em> 10(8): ev10.i08. https:\/\/doi.org\/10.1371\/image.pbio.v10.i08 \u00a9 Chen.<\/p>\r\n
Mayo Clinic. (2013). The heart and circulatory system - How they work. YouTube. https:\/\/www.youtube.com\/watch?v=CWFyxn0qDEU&t=1s<\/p>\r\n
TED-Ed. (2014, May 20). How the heart actually pumps blood - Edmond Hui. YouTube. https:\/\/www.youtube.com\/watch?v=ruM4Xxhx32U&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\n
Figure 14.2.1 What are these strange tunnels?<\/em><\/figcaption><\/figure>\n \nAnt Hill or Plumbing System?<\/h1>\n<\/div>\n
What do you think the picture in Figure 14.2.1 shows? Is it a maze of underground passageways in an ant hill? A network of interconnected pipes in a complex plumbing system? The picture actually shows something that, like ant tunnels and plumbing pipes, functions as a transportation system. It shows a network of blood vessels, which are part of the cardiovascular system.<\/p>\n
\nWhat is the Cardiovascular System?<\/h1>\n<\/div>\n
The\u00a0cardiovascular system<\/a><\/strong>, also called the circulatory system, is the organ system that transports materials to and from all the cells of the body. The materials carried by the cardiovascular system include oxygen from the lungs<\/a>, nutrients from the digestive system<\/a>, hormones<\/a> from glands of the endocrine system<\/a>, and waste materials from cells throughout the body. Transport of these and many other materials is necessary to maintain homeostasis<\/a> of the body. The main components of the cardiovascular system are the heart, blood vessels, and blood. Each of these components is shown in Figure 14.2.2 and introduced below.<\/p>\n
Figure 14.2.2 This simplified drawing of the cardiovascular system shows its main structures. The heart is shown in the chest in red. Blood vessels called arteries are also shown in red, and blood vessels called veins are shown in blue.<\/em><\/figcaption><\/figure>\n \nHeart<\/h1>\n<\/div>\n
The\u00a0heart<\/a><\/strong> is a muscular organ in the chest. It consists mainly of cardiac muscle<\/a> tissue, and it pumps blood through blood vessels by repeated, rhythmic contractions. As shown in Figure 14.2.3, the heart has four inner chambers: a right atrium and ventricle, and a left atrium and ventricle. On each side of the heart, blood is pumped from the atrium to the ventricle below it, and from the ventricle out of the heart. The heart also contains several valves that allow blood to flow only in the proper direction through the heart.<\/p>\n
Figure 14.2.3 The right side of the heart includes the right atrium and right ventricle. The left side includes the left atrium and left ventricle.<\/em><\/figcaption><\/figure>\n <\/p>\n
As you may have noticed, the Figure 14.2.3 diagram labels the right side of the heart on the left side of the diagram, and vice versa.\u00a0 This is because it is assumed that in this diagram, the heart appears\u00a0 as if the patient was facing us – the patient’s left side is on our right side!<\/p>\n
Unlike skeletal muscle, cardiac muscle routinely contracts without stimulation by the\u00a0nervous system. Specialized cardiac muscle\u00a0cells\u00a0send out electrical impulses that stimulate the contractions. As a result, the atria and ventricles normally contract with just the right timing to keep blood pumping efficiently through the heart.<\/p>\n
\nBlood Vessels<\/h1>\n<\/div>\n
The blood vessels<\/a> of the cardiovascular system are like a network of interconnected, one-way roads that range from superhighways to back alleys. Like a network of roads, the blood vessels are tasked with allowing the transport of materials from one place to another. There are three major types of blood vessels: arteries, veins, and capillaries. They are illustrated in Figure 14.2.4 and described below.<\/p>\n
Figure 14.2.4 This diagram represents the structure and functions of the different types of blood vessels in the cardiovascular system.<\/em><\/figcaption><\/figure>\n - \n
- Arteries<\/a><\/strong>\u00a0are blood vessels that carry blood away from the heart (except for the arteries that actually supply blood to the heart muscle). Most arteries carry oxygen-rich blood, and one of their main functions is distributing oxygen to tissues throughout the body. The smallest arteries are called arterioles.<\/li>\n
- Veins<\/a><\/strong>\u00a0are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood. The smallest veins are called venules.<\/li>\n
- Capillaries<\/a><\/strong>\u00a0are the smallest blood vessels, and they connect arterioles and venules. As they pass through tissues, they exchange substances (including oxygen) with\u00a0cells.<\/li>\n<\/ul>\n
\nTwo Circulations<\/h1>\n<\/div>\n
Cells throughout the body need a constant supply of oxygen. They get oxygen from capillaries in the systemic circulation. The systemic circulation is just one of two interconnected circulations that make up the human cardiovascular system. The other circulation is the pulmonary system, which is where blood picks up oxygen to carry to cells. It takes blood about 20 seconds to make one complete transit through both circulations (see Figure 14.2.5).<\/p>\n
Figure 14.2.5 There are two main circuits through which blood flows in the cardiovascular system. In the pulmonary circuit, blood moves from the right side of the heart to the lungs and then back to the left side of the heart. In the systemic circuit, blood moves from the left side of the heart to the body tissues and then back to the right side of the heart.<\/em><\/figcaption><\/figure>\n Pulmonary Circuit<\/h2>\n
The\u00a0pulmonary<\/strong>\u00a0<\/strong>circuit<\/strong><\/a> involves only the heart, the lungs, and the major blood vessels that connect them (illustrated in Figure 14.2.6). Blood moves through the pulmonary circuit from the heart, to the lungs, and then back to the heart again, becoming oxygenated in the process. Specifically, the right ventricle of the heart pumps deoxygenated blood into the right and left pulmonary arteries. These arteries carry the blood to the right and left lungs, respectively. Oxygenated blood then returns from the right and left lungs through the two right and two left pulmonary veins. All four pulmonary veins enter the left atrium of the heart.<\/p>\n
Figure 14.2.6 This diagram shows the heart, lungs, and major vessels that make up the pulmonary circulation. The coloured arrows indicate the direction of blood flow \u2014 red for oxygenated blood and blue for relatively deoxygenated blood.<\/em><\/figcaption><\/figure>\n What happens to the blood while it is in the lungs? It passes through increasingly smaller arteries, and finally through capillary networks surrounding the alveoli (see Figure 14.2.7). This is where gas exchange takes place. The deoxygenated blood in the capillaries picks up oxygen from the alveoli, and gives up carbon dioxide to the alveoli. As a result, the blood returning to the heart in the pulmonary veins is almost completely saturated with oxygen.<\/p>\n
Figure 14.2.7 This diagram illustrates clusters of alveoli in the lungs, where gas exchange takes place with blood in capillaries as it passes through the pulmonary circulation.<\/em><\/figcaption><\/figure>\n Systemic Circulation<\/h2>\n
The oxygenated blood that enters the left atrium of the heart in the pulmonary circulation then passes into the\u00a0systemic circuit<\/a>.<\/strong>\u00a0This is the part of the cardiovascular system that transports blood to and from all of the tissues of the body to provide oxygen and\u00a0nutrients, and to pick up wastes. It consists of the heart and blood vessels that supply the metabolic needs of all the cells in the body, including those of the heart and lungs.<\/p>\n
As shown in Figure 14.2.8, in the systemic circulation, the left atrium pumps oxygenated blood to the left ventricle, which pumps the blood directly into the aorta, the body\u2019s largest artery. Major arteries branching off the aorta carry the blood to the head and upper extremities. The aorta continues down through the abdomen and carries blood to the abdomen and lower extremities. The blood then returns to the heart through the network of increasingly larger veins of the systemic circulation. All of the returning blood eventually collects in the superior vena cava (upper body) and inferior vena cava (lower body), which empty directly into the right atrium of the heart.<\/p>\n
Figure 14.2.8 The systemic circulation includes the aorta (red), which carries oxygenated blood away from the heart to the rest of the body; and the inferior and superior venae cavae (blue), which return deoxygenated blood to the heart from the body. The coloured arrows in the diagram indicate the direction of blood flow \u2014 red for oxygenated and blue for deoxygenated.<\/em><\/figcaption><\/figure>\n Blood<\/h2>\n
Figure 14.2.9 The three types of cells in blood are pictured here: red blood cell (left), platelet (center), and white blood cell (right).<\/em><\/figcaption><\/figure>\n Blood<\/a><\/strong>\u00a0is a fluid connective tissue that circulates throughout the body in blood vessels by the pumping action of the heart. Blood carries oxygen and\u00a0nutrients\u00a0to all the body\u2019s cells, and it carries carbon dioxide and other wastes away from the cells to be excreted. Blood also transports many other substances, defends the body against infection, repairs\u00a0body tissues, and controls the body\u2019s\u00a0pH<\/a>, among other functions.<\/p>\n
The fluid part of blood is called\u00a0plasma<\/a><\/strong>. It is a yellowish, watery liquid that contains many dissolved substances and blood cells. Types of blood cells in plasma include red blood cells, white blood cells, and platelets, all of which are illustrated in the photomicrograph (Figure 14.2.9) and described below.<\/p>\n
- \n
- Erythrocytes<\/a> <\/strong>(red blood cells)\u00a0have the main function of carrying oxygen in the blood. Red blood cells consist mostly of\u00a0hemoglobin<\/a><\/strong>, a\u00a0protein\u00a0containing iron that binds with oxygen.<\/li>\n
- Leukocytes<\/a> <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\n
- Thrombocytes<\/a><\/strong> (platelets)\u00a0are cell fragments involved in blood clotting. They stick to tears in blood vessels and to each other, forming a plug at the site of injury. They also release chemicals that are needed for clotting to occur.<\/li>\n<\/ul>\n
\n\n\n 14.2 Summary<\/span><\/h1>\n<\/header>\n
\n- \n
- The cardiovascular system<\/a> is the organ system that transports materials to and from all the cells of the body. The main components of the cardiovascular system are the heart<\/a>, blood vessels<\/a>, and blood<\/a>.<\/li>\n
- The heart is a muscular organ in the chest that consists mainly of cardiac muscle and pumps blood through blood vessels by repeated, rhythmic contractions. The heart has four chambers through which blood flows, and valves that keep blood flowing in just one direction.<\/li>\n
- Blood vessels carry blood throughout the body. Major types of blood vessels are arteries (which mainly carry blood away from the heart), veins (which carry blood toward the heart), and capillaries (which exchange substances between the blood and cells of the body).<\/li>\n
- The cardiovascular system has two interconnected circulations. The pulmonary circuit<\/a> carries blood between the heart and lungs, where blood is oxygenated. The systemic circuit<\/a> carries blood between the heart and the rest of the body, where it delivers oxygen.<\/li>\n
- Blood is a fluid connective tissue<\/a> that circulates throughout the body in blood vessels. It consists of a\u00a0liquid\u00a0part \u2014 called\u00a0plasma<\/a> \u2014 which contains many dissolved substances, and cells, including erythrocytes<\/a>, leukocytes<\/a> and thrombocytes<\/a>.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\n\n 14.2 Review Questions<\/span><\/h1>\n<\/header>\n
\n- \n
- Describe the heart and how it functions.<\/li>\n
- Compare and contrast the pulmonary and systemic circulations.<\/li>\n
- \n\n
- Leukocytes<\/a> <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\n
- Veins<\/a><\/strong>\u00a0are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood. The smallest veins are called venules.<\/li>\n
- Arteries<\/a><\/strong>\u00a0are blood vessels that carry blood away from the heart (except for the arteries that actually supply blood to the heart muscle). Most arteries carry oxygen-rich blood, and one of their main functions is distributing oxygen to tissues throughout the body. The smallest arteries are called arterioles.<\/li>\n
- [pb_glossary id=\"5623\"]Leukocytes[\/pb_glossary] <\/strong>(white blood cells)\u00a0are far fewer in number than red blood cells. They defend the body in various ways.\u00a0White blood cells called phagocytes, for example, swallow and destroy pathogens, dead cells, and other debris in the blood.<\/li>\r\n \t
![Circulatory_System_no_tags.svg<\/a> by Mariana Ruiz Villarreal [](\"https:\/\/commons.wikimedia.org\/wiki\/File:Circulatory_System_no_tags.svg\"){kind=link}
![Blausen_0462_HeartAnatomy<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Blausen_0462_HeartAnatomy.png\"){kind=link}
![2101_Blood_Flow_Through_the_Heart<\/a>\u00a0by](\"https:\/\/commons.wikimedia.org\/wiki\/File:2101_Blood_Flow_Through_the_Heart.jpg\"){kind=link}
![Illu_pulmonary_circuit<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Illu_pulmonary_circuit.jpg\"){kind=link}
![Pulmonary_Blood_Circulation<\/a> by Artwork by Holly Fischer from](\"https:\/\/commons.wikimedia.org\/wiki\/File:Pulmonary_Blood_Circulation.png\"){kind=link}
![systemic_circuit.svg<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Illu_systemic_circuit.svg\"){kind=link}
![Red_White_Blood_cells<\/a> by Electron Microscopy Facility at The National Cancer Institute at Frederick (NCI-Frederick) on Wikimedia Commons is in the](\"https:\/\/commons.wikimedia.org\/wiki\/File:Red_White_Blood_cells.jpg\"){kind=link}