{"id":93,"date":"2019-09-18T19:43:07","date_gmt":"2019-09-18T19:43:07","guid":{"rendered":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/chapter\/cardiovascular-system\/"},"modified":"2025-03-04T21:13:00","modified_gmt":"2025-03-04T21:13:00","slug":"cardiovascular-system","status":"publish","type":"chapter","link":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/chapter\/cardiovascular-system\/","title":{"raw":"Cardiovascular System","rendered":"Cardiovascular System"},"content":{"raw":"<div class=\"textbox textbox--learning-objectives\"><header class=\"textbox__header\">\n<h3 class=\"textbox__title\"><em>Learning Objectives<\/em><\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n \t<li>Examine the anatomy of the heart<\/li>\n \t<li>Determine the main functions of the cardiovascular system<\/li>\n \t<li>Differentiate cardiovascular system medical terms and common abbreviations<\/li>\n \t<li>Recognize the medical specialties associated with the cardiovascular system<\/li>\n \t<li>Discover common diseases, disorders, and procedures related to the cardiovascular system<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<h2>Cardiovascular System Word Parts<\/h2>\nClick on prefixes, combining forms, and suffixes to reveal a list of word parts to memorize for the cardiovascular system.\n\n&nbsp;\n\n[h5p id=\"49\"]\n<h2>Introduction to the Cardiovascular System<\/h2>\n<p id=\"fs-id1894016\">The cardiovascular system is made of three components: the heart, vessels, and blood. The heart is a fist-sized vital organ that has <em>one<\/em> job: to pump blood. If one assumes an average [pb_glossary id=\"369\"]heart rate[\/pb_glossary] of 75 beats per minute, a human heart would beat approximately 108,000 times in one day, more than 39 million times in one year, and nearly 3 billion times during a 75-year lifespan. At rest, each of the major pumping chambers of the heart ejects approximately 70 mL of blood per contraction in an adult. This would be equal to 5.25 liters of blood per minute and approximately 14,000 liters per day. Over one year, that would equal 10,000,000 liters of blood sent through roughly 100,000 km of blood vessels. In order to understand how that happens, it is necessary to understand the anatomy and physiology of the heart.<\/p>\n\n<h3>Watch this video:<\/h3>\n<div class=\"textbox shaded\">\n\n[embed]https:\/\/youtu.be\/X9ZZ6tcxArI?t=2[\/embed]\n\n<em>Media 9.1. <a href=\"https:\/\/youtu.be\/X9ZZ6tcxArI\">The Heart, Part 1 - Under Pressure: Crash Course A&amp;P #25<\/a> [Online video]. Copyright 2015 by <a href=\"https:\/\/www.youtube.com\/channel\/UCX6b17PVsYBQ0ip5gyeme-Q\">CrashCourse<\/a>.<\/em>\n\n<\/div>\n<h2 id=\"fs-id2281225\">Practice Medical Terms Related to the Cardiovascular System<\/h2>\n<section>[h5p id=\"50\"]\n<h2>Anatomy of the Heart<\/h2>\n<h3 id=\"fs-id1892589\">Location<\/h3>\nThe human heart is located within the thoracic cavity, between the lungs in the space known as the <strong>mediastinum<\/strong>. <a href=\"#Figure9.1\">Figure 9.1<\/a> shows the position of the heart within the thoracic cavity. Within the mediastinum, the heart is separated from the other mediastinal structures by a tough membrane known as the pericardium, or pericardial sac, and sits in its own space called the <strong>pericardial cavity<\/strong>. The [pb_glossary id=\"370\"]great vessels[\/pb_glossary], which carry blood to and from the heart, are attached to the superior surface of the heart, which is called the base. The base of the heart is located at the level of the third costal cartilage. The inferior tip of the heart, the apex, lies just to the left of the sternum between the junction of the fourth and fifth ribs.\n\n&nbsp;\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\n<h3 class=\"textbox__title\">Concept Check<\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n \t<li>On the diagram below (Figure 1), locate the <strong>mediastinum<\/strong>, the <strong>pericardial cavity<\/strong>, the <strong>base<\/strong> of the heart and the <strong>apex<\/strong> of the heart.<\/li>\n \t<li>Locate the largest vein in the body, the <strong>superior vena cava<\/strong>.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<figure id=\"fig-ch20_01_01\"><figcaption><\/figcaption>[caption id=\"\" align=\"aligncenter\" width=\"666\"]<img src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2001_Heart_Position_in_ThoraxN.jpg\" alt=\"Location of the heart in the thorax. Image description available.\" width=\"666\" height=\"605\"> <a id=\"Figure9.1\" href=\"\"><\/a>Figure 9.1. Position of the Heart in the Thorax. The heart is located within the thoracic cavity, medially between the lungs in the mediastinum. It is about the size of a fist, is broad at the top, and tapers toward the base. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.1id\">[Image description.]<\/a>[\/caption]<\/figure>\n<\/section><section id=\"fs-id3028596\">\n<h3 id=\"fs-id2959986\">Membranes and Layers of the Heart Walls<\/h3>\nThe heart and the [pb_glossary id=\"373\"]roots of the great vessels[\/pb_glossary] are surrounded by a membrane known as the <strong>pericardium<\/strong> or <strong>pericardial sac<\/strong>. The pericardium consists of two distinct sub layers:\n<ul>\n \t<li>The sturdy outer fibrous pericardium is made of tough, dense connective tissue that protects the heart and holds it in position.<\/li>\n \t<li>Separated by the <strong>pericardial<\/strong> <strong>cavity <\/strong>and containing pericardial fluid the inner [pb_glossary id=\"372\"]serous[\/pb_glossary] pericardium consists of two layers:\n<ul>\n \t<li>the outer <strong>parietal pericardium<\/strong>, which is fused to the fibrous pericardium.<\/li>\n \t<li>the inner <strong>visceral pericardium<\/strong>, or <strong>epicardium<\/strong>, which is fused to the heart and forms the outer layer of the heart wall.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p id=\"fs-id2418328\">The walls of the heart consist of three layers:<\/p>\n\n<ul>\n \t<li>The outer <strong>epicardium<\/strong>, which is another name for the visceral pericardium mentioned above.<\/li>\n \t<li>The thick, middle <strong>myocardium<\/strong>, which is made of muscle tissue and gives the heart its ability to contract.<\/li>\n \t<li>The inner <strong>endocardium<\/strong>, which lines the heart chambers and is the main component of the heart valves.<\/li>\n<\/ul>\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\n<h3 class=\"textbox__title\">Concept Check<\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n \t<li>Look at <a href=\"#Figure9.2\">Figure 9.2<\/a> below, and name the layers of the heart wall and surrounding membranes, starting with the innermost layer.<\/li>\n \t<li>As shown on the diagram, suggest why the <strong>myocardium<\/strong> layer is thicker than the <strong>endocardium<\/strong> layer.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n&nbsp;\n<figure id=\"fig-ch20_01_04\">[caption id=\"\" align=\"aligncenter\" width=\"627\"]<img src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2004_Heart_Wall.jpg\" alt=\"Magnified view of the heart's wall. Image description available.\" width=\"627\" height=\"435\"> <a id=\"Figure9.2\" href=\"\"><\/a>Figure 9.2. Pericardial Membranes and Layers of the Heart Wall. The pericardial membrane that surrounds the heart consists of three layers and the pericardial cavity. The heart wall also consists of three layers. The pericardial membrane and the heart wall share the epicardium From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.2id\">[Image description.]<\/a>[\/caption]<\/figure>\n<h3>Internal Structures of the Heart<\/h3>\nThe heart consists of four chambers:\n<ul>\n \t<li>The upper chambers are the right and left <strong>atria<\/strong> (singular: atrium).<\/li>\n \t<li>The lower chambers are the right and left <strong>ventricles.<\/strong><\/li>\n<\/ul>\nThe <strong>interventricular septum<\/strong> is a muscular wall that separates the right and left ventricles. The interatrial septum separates the right and left atria.\n\nThe atrium and ventricle on each side of the heart are separated by an atrioventricular (AV) valve:\n<ul>\n \t<li>The right AV valve, or <strong>tricuspid valve,<\/strong> separates the right atrium and right ventricle.<\/li>\n \t<li>The left AV valve, or <strong>bicuspid valve, <\/strong>separates the left ventricle and the left atrium. This valve is also called the <strong>mitral valve.<\/strong><\/li>\n<\/ul>\nThere are also two semilunar valves:\n<ul>\n \t<li>The <strong>pulmonary valve<\/strong> separates the right ventricle from the pulmonary trunk.<\/li>\n \t<li>The <strong>aortic valve<\/strong> separates the left ventricle from the aorta.<\/li>\n<\/ul>\n<h2>Anatomy Labeling Activity<\/h2>\n[h5p id=\"51\"]\n\n<\/section>\n<h2>Physiology of the Heart<\/h2>\n<section id=\"fs-id1987886\">In order for the heart to do its job of pumping blood to the lungs and the body, nutrients and oxygen must be supplied to the cells of the heart. The heart also needs to coordinate its contractions so that all parts are working together to pump blood effectively. To understand how all of this works together to give the heart its ability to pump blood, we will examine three interdependent aspects of heart function.\n<ol>\n \t<li>Circulation through the heart: Blood is pumped by the heart in order to provide oxygen and nutrients to every cell in the body.<\/li>\n \t<li>The heart as an organ (coronary blood supply): The heart is an organ, made of cells and tissues which require their own blood supply.<\/li>\n \t<li>The heart's electrical conduction system: The heart is able to independently generate and transmit instructions to the myocardium in order to make it contract and pump the blood.<\/li>\n<\/ol>\n<h3>1. Circulation Through the Heart: The Heart as a Pump<\/h3>\n<p id=\"fs-id2767147\">The heart pumps blood to two distinct but linked circulatory systems called the pulmonary and systemic circuits. The <strong>pulmonary circuit<\/strong> transports blood to and from the lungs, where it picks up oxygen and drops off carbon dioxide. The <strong>systemic circuit<\/strong> transports freshly oxygenated blood to virtually all of the tissues of the body and returns relatively deoxygenated blood and carbon dioxide to the heart to be sent back to the pulmonary circulation.<\/p>\n\n<ol>\n \t<li>Blood that is carrying carbon dioxide and waste products from the body tissues is returned to the <strong>right atrium<\/strong> via the [pb_glossary id=\"375\"]superior vena cava[\/pb_glossary] and the [pb_glossary id=\"376\"]inferior vena cava[\/pb_glossary].<\/li>\n \t<li>From the right atrium, the deoxygenated blood moves through the <strong>tricuspid valve<\/strong> into the right ventricle.<\/li>\n \t<li>The <strong>right ventricle<\/strong> pumps deoxygenated blood through the <strong>pulmonary valve<\/strong> into the <strong>[pb_glossary id=\"421\"]pulmonary trunk[\/pb_glossary]<\/strong>, which splits into the <strong>right and left pulmonary arteries<\/strong>, leading toward the lungs. These arteries branch many times before reaching the <strong>pulmonary capillaries<\/strong>, where gas exchange occurs: carbon dioxide exits the blood, and oxygen enters. The pulmonary arteries are the only arteries in the postnatal body that carries deoxygenated blood. Did you notice that they are often colored blue on diagrams of the heart?<\/li>\n \t<li>Freshly oxygenated blood returns from the lungs to the <strong>left atrium<\/strong> via the <strong>pulmonary veins<\/strong>. These veins are the only postnatal veins in the body that carry highly oxygenated blood and are often colored red on heart images.<\/li>\n \t<li>From the left atrium, the blood moves through the <strong>mitral valve<\/strong> into the <strong>left ventricle. <\/strong><\/li>\n \t<li>The left ventricle pumps blood through the <strong>aortic valve<\/strong>, into the <strong>aorta<\/strong>, delivering blood to all parts of the body.<\/li>\n<\/ol>\n<\/section>\n<div class=\"textbox textbox--key-takeaways\"><header class=\"textbox__header\">\n<h3 class=\"textbox__title\"><em>Did you know?<\/em><\/h3>\n<\/header>\n<div class=\"textbox__content\">\n\n<span class=\"tight\">The heart sounds heard through a stethoscope are the sounds of the four heart valves opening and closing at specific times during one cardiac cycle.<\/span>\n\n<\/div>\n<\/div>\n<section id=\"fs-id1987886\">\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\n<h3 class=\"textbox__title\">Concept Check<\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n \t<li>On <a href=\"#Figure9.3\">Figure 9.3<\/a> below, use your finger to trace the pathway of blood flowing through the right side of the heart, naming each of the following structures as you encounter them: Superior and inferior venae cavae, right atrium, tricuspid valve, right ventricle, pulmonary valve, right and left pulmonary arteries.<\/li>\n \t<li>Suggest what would happen if the <strong>aorta<\/strong> experienced a blockage or constriction.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/section>\n<figure id=\"fig-ch20_01_03\">[caption id=\"attachment_92\" align=\"aligncenter\" width=\"692\"]<img class=\"wp-image-92\" src=\"https:\/\/pressbooks.ccconline.org\/accphysicalgeology\/wp-content\/uploads\/sites\/228\/2019\/09\/22489f4ba975acba9cff1daae384b2cacb46705a-1024x590.jpg\" alt=\"\" width=\"692\" height=\"398\"> <a id=\"Figure9.3\" href=\"\"><\/a>Figure 9.3. Pulmonary Circuit Blood exiting from the right ventricle flows into the pulmonary trunk, which bifurcates into the two pulmonary arteries. These vessels branch to supply blood to the pulmonary capillaries, where gas exchange occurs within the lung alveoli. Blood returns via the pulmonary veins to the left atrium. From Betts et al., 2013. Licensed under CC BY 4.0. [<a href=\"#Figure9.3id\">Image description<\/a>.][\/caption]\n<h4>Pulmonary Circuit<\/h4>\nBlood exiting from the right ventricle flows into the pulmonary trunk, which bifurcates into the two pulmonary arteries. These vessels branch to supply blood to the pulmonary capillaries, where gas exchange occurs within the lung alveoli. Blood returns via the pulmonary veins to the left atrium.\n\n&nbsp;\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\n<h3 class=\"textbox__title\">Concept Check<\/h3>\n<\/header>\n<div class=\"textbox__content\">\n\nOn <a href=\"#Figure9.4\">Figure 9.4<\/a> below, use your finger to trace the pathway of blood flowing through the left side of the heart, naming each of the following structures as you encounter them: right and left pulmonary veins, left atrium, mitral valve, left ventricle, aortic valve, aorta.\n\n<\/div>\n<\/div>\n[caption id=\"\" align=\"aligncenter\" width=\"775\"]<img src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2003_Dual_System_of_Human_Circulation.jpg\" alt=\"Diagram of heart and circulatory system showing direction of blood flow. Image description available.\" width=\"775\" height=\"855\"> <a id=\"Figure9.4\" href=\"\"><\/a>Figure 9.4. Dual System of the Human Blood Circulation. Blood flows from the right atrium to the right ventricle, where it is pumped into the pulmonary circuit. The blood in the pulmonary artery branches is low in oxygen but relatively high in carbon dioxide. Gas exchange occurs in the pulmonary capillaries (oxygen into the blood, carbon dioxide out), and blood high in oxygen and low in carbon dioxide is returned to the left atrium. From here, blood enters the left ventricle, which pumps it into the systemic circuit. Following the exchange in the systemic capillaries (oxygen and nutrients out of the capillaries and carbon dioxide and wastes in), blood returns to the right atrium and the cycle is repeated. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.4id\">[Image description.]<\/a>[\/caption]\n<h4>Cardiac Cycle<\/h4>\nThe process of pumping and circulating blood is active, coordinated, and rhythmic. Each heartbeat represents one cycle of the heart receiving blood and ejecting blood.\n<ul>\n \t<li><strong>Diastole<\/strong> is the portion of the cycle in which the heart is relaxed and the atria and ventricles are filling with blood. The AV valves are open so that blood can move from the atria to the ventricles.<\/li>\n \t<li><strong style=\"text-align: initial;font-size: 1em\">Systole<\/strong><span style=\"text-align: initial;font-size: 1em\"> is the portion of the cycle in which the heart contracts, AV valves slam shut, and the ventricles eject blood to the lungs and the body through the open semilunar valves. Once this phase ends, the semilunar valves close, in preparation for another filling phase.<\/span><\/li>\n<\/ul>\n<h3>2. The Heart as an Organ: The Coronary Blood Supply<\/h3>\nMyocardial cells require their own blood supply to carry out their function of contracting and relaxing the heart in order to pump blood. Their own blood supply provides nutrients and oxygen and carries away carbon dioxide and waste. These functions are provided by the coronary arteries and coronary veins.\n\n&nbsp;\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\n<h3 class=\"textbox__title\">Concept Check<\/h3>\n<\/header>\n<div class=\"textbox__content\">\n\nOn the <a href=\"#Figure9.5\">image<\/a> below, locate the three main coronary arteries:\n<ul>\n \t<li><strong>Anterior interventricular artery<\/strong> (more commonly known as the <strong>left anterior descending artery, or LAD<\/strong>)<\/li>\n \t<li><strong>Circumflex artery (Cx)<\/strong><\/li>\n \t<li><strong>Right coronary artery (RCA)<\/strong><\/li>\n<\/ul>\nFollow the path of each of these three arteries to try to determine which parts of the myocardium each artery (along with its many smaller branches) supplies with blood.\n\n<\/div>\n<\/div>\n[caption id=\"\" align=\"aligncenter\" width=\"678\"]<img class=\"\" src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2014ab_Coronary_Blood_Vessels.jpg\" alt=\"Anterior and posterior views of the heart and its blood vessels. Image description available.\" width=\"678\" height=\"623\"> <a id=\"Figure9.5\" href=\"\"><\/a>Figure 9.5 Coronary Circulation. The anterior view of the heart shows the prominent coronary surface vessels. The posterior view of the heart shows the prominent coronary surface vessels. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.5id\">[Image description.]<\/a>[\/caption]\n<h3>3. The Heart's Electrical Conduction System<\/h3>\nIn order for all parts of the heart to work together to beat regularly and effectively, the heart has its own electrical system, which initiates and conducts each heartbeat through the entire myocardium. Specialized groups of heart cells perform this function all on their own, without requiring messages from the central nervous system.<\/figure>\n<h4>Watch this video:<\/h4>\n<div class=\"textbox shaded\">\n\n[embed]https:\/\/youtu.be\/FLBMwcvOaEo[\/embed]\n\n<em>Media 9.2. <a href=\"https:\/\/youtu.be\/FLBMwcvOaEo\">The Heart, Part 2 - Heart Throbs: Crash Course A&amp;P #26<\/a> [Online video]. Copyright 2015 by <a href=\"https:\/\/www.youtube.com\/channel\/UCX6b17PVsYBQ0ip5gyeme-Q\">CrashCourse<\/a>.<\/em>\n\n<\/div>\n[caption id=\"\" align=\"aligncenter\" width=\"805\"]<img class=\"\" src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2018_Conduction_System_of_Heart.jpg\" alt=\"Anterior view of frontal section of the heart. Image description available.\" width=\"805\" height=\"540\"> <a id=\"Figure9.6\" href=\"\"><\/a>Figure 9.6. Conduction System of the Heart. Specialized conducting components of the heart include the sinoatrial node, the internodal pathways, the atrioventricular node, the atrioventricular bundle, the right and left bundle branches, and the Purkinje fibers. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.6id\">[Image description.]<\/a>[\/caption]\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\n<h3 class=\"textbox__title\">Concept Check<\/h3>\n<\/header>\n<div class=\"textbox__content\">\n\nOn the <a href=\"#Figure9.6\">image<\/a> above, trace the electrical impulse generated by the heart's pacemaker (the <strong>sinoatrial node<\/strong>, or <strong>SA node<\/strong>) through the rest of the conduction system, including the <strong>atrioventricular (AV) node<\/strong>, the <strong>atrioventricular bundle (bundle of His)<\/strong>, the <strong>right and left bundle branches<\/strong>, and the <strong>Purkinje fibers<\/strong>.\n\n<\/div>\n<\/div>\nWe can detect and record the electrical activity of the heart's conduction system using an electrocardiogram (ECG or EKG). <a href=\"#Figure9.7\">Figure 9.7<\/a> shows the electrical impulse originating in the SA node (step 2) and traveling through the heart's conduction system, allowing the heart to complete one cardiac cycle. Each waveform on the ECG tracing represents electricity moving through and affecting a different part of the heart. Did you notice that the [pb_glossary id=\"410\"]AV valves[\/pb_glossary] close when the electrical impulse reaches the ventricles, just before systole occurs?\n\n[caption id=\"\" align=\"aligncenter\" width=\"2206\"]<img src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2023_ECG_Tracing_with_Heart_ContractionN.jpg\" alt=\"ECG tracing correlated to the cardiac cycle. Image description available. \" width=\"2206\" height=\"1613\"> <a id=\"Figure9.7\" href=\"\"><\/a>Figure 9.7. ECG Tracing Correlated to the Cardiac Cycle. This diagram correlates an ECG tracing with the electrical and mechanical events of a heart contraction. Each segment of an ECG tracing corresponds to one event in the cardiac cycle. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.7id\">[Image description.]<\/a>[\/caption]\n<h2>Practice Terms Related to the Cardiovascular System<\/h2>\n[h5p id=\"52\"]\n<h2>Common Abbreviations for the Cardiovascular System<\/h2>\nMany terms and phrases related to the cardiovascular system are abbreviated. Learn these common abbreviations by expanding the list below.\n\n&nbsp;\n\n[h5p id=\"53\"]\n<h2>Diseases and Disorders of the Heart<\/h2>\n<h3>Cardiomyopathy<\/h3>\nThe heart of a well-trained athlete can be considerably larger than the average person's heart. This is because exercise results in an increase in muscle cells called [pb_glossary id=\"289\"]hypertrophy[\/pb_glossary]. Hearts of athletes can pump blood more effectively at lower rates than those of non-athletes. However, when an enlarged heart is not the result of exercise, it may be due to <strong>hypertrophic cardiomyopathy<\/strong>. The cause of an abnormally enlarged heart muscle is unknown, but the condition is often undiagnosed and can cause sudden death in apparently otherwise healthy young people.\n\nOther types of cardiomyopathy include:\n<ul>\n \t<li><strong>Dilated cardiomyopathy<\/strong>, which also has an unknown cause and is seen in people of any age. In this disorder, one of the ventricles of the heart is larger than normal.<\/li>\n \t<li><strong>Arrhythmogenic cardiomyopathy<\/strong>, an inherited condition that results in irregular heart rhythms.<\/li>\n \t<li><strong>Restrictive cardiomyopathy<\/strong>, which is a complication of other conditions which cause the myocardium to scar or stiffen (Centers for Disease Control and Prevention, 2019).<\/li>\n<\/ul>\nCardiomyopathy may also be caused by myocardial infarctions, myocardial infections, pregnancy, alcohol or cocaine abuse, autoimmune and endocrine diseases. Because the myocardium is responsible for contracting and pumping blood, patients with cardiomyopathy experience impaired heart function which may lead to heart failure (Centers for Disease Control and Prevention, n.d.-a). To learn more, visit the <a href=\"https:\/\/www.cdc.gov\/heartdisease\/cardiomyopathy.htm\">Centers for Disease Control and Prevention's web page on cardiomyopathy.<\/a>\n<h3 id=\"fig-ch20_01_08\">Heart Failure<\/h3>\n<strong>Heart failure<\/strong> is defined as the inability of the heart to pump enough blood to meet the needs of the body. It is also called <strong>congestive heart failure (CHF). <\/strong>This condition causes swelling in the lower extremities and shortness of breath, due to a buildup of fluid in the lungs. It may be caused by cardiomyopathy, and it may lead to [pb_glossary id=\"250\"]hypertension[\/pb_glossary] and heart valve disorders (Heart &amp; Stroke, n.d.). To learn more, visit the <a href=\"https:\/\/www.heart.org\/en\/health-topics\/heart-failure\/what-is-heart-failure\">American Heart Association's web page on heart failure<\/a>.\n<h3>Valvular Heart Disease<\/h3>\nThe four heart valves open and close at specific times during the cardiac cycle, in order to ensure that blood flows in only one direction through the heart. This requires that these valves open and close completely. Infections such as rheumatic disease or bacterial endocarditis can affect the heart valves and result in scar tissue formation which interferes with valve function. Other causes of heart valve disease include congenitally malformed valves, autoimmune diseases, and other cardiovascular diseases such as aortic aneurysms and atherosclerosis (Centers for Disease Control and Prevention, n.d.-b).\n\nHeart valve disease may be [pb_glossary id=\"258\"]asymptomatic[\/pb_glossary] or cause [pb_glossary id=\"295\"]dyspnea[\/pb_glossary], [pb_glossary id=\"411\"]arrhythmias[\/pb_glossary], fatigue and other symptoms. It is often detected when a [pb_glossary id=\"385\"]heart murmur[\/pb_glossary] is heard through a stethoscope (Centers for Disease Control and Prevention, n.d.-b).\n<ul>\n \t<li><strong>Mitral Valve <\/strong><b>Prolapse<\/b>\n<ul>\n \t<li>The mitral (bicuspid) valve is diseased or malformed and is not able to close completely, allowing the regurgitation of blood back into the left atrium during systole. Because some of the blood goes back into the atrium, insufficient blood is pumped out of the ventricle into the systemic circulation. This inability to close properly and the resulting regurgitation may also be found in other heart valves (Centers for Disease Control and Prevention, n.d.-b).<\/li>\n<\/ul>\n<\/li>\n \t<li><strong>Aortic Stenosis<\/strong>\n<ul>\n \t<li>The aortic valve is narrowed and hardened, preventing it from opening fully and allowing sufficient blood to travel to the systemic circulation. Any heart valve can be stenosed, but this disorder most often affects the aortic valve (Centers for Disease Control and Prevention, n.d.-b).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\nVisit the <a href=\"https:\/\/www.cdc.gov\/heartdisease\/valvular_disease.htm\">Center for Disease Control and Prevention's web page on valvular heart disease<\/a> to learn more.\n<h3>Aneurysms<\/h3>\nAn aneurysm is a defect in the wall of an artery in which the wall becomes thin and weak and starts to balloon out as blood pulses against the vessel wall. This can happen to any artery and even to the myocardial walls. Aneurysms sometimes occur in the portion of the aorta that is in the thorax (see <a href=\"#Figure9.8\">Figure 9.8<\/a>). If these aneurysms start to leak between layers of the vessel wall, the condition is known as aortic dissection. If an aortic or cardiac aneurysm bursts, there is sudden, massive internal bleeding (Centers for Disease Control and Prevention, n.d.-c).\n<figure>[caption id=\"\" align=\"aligncenter\" width=\"380\"]<img src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2124_Thoracic_Abdominal_Arteries.jpg\" alt=\"Thoracic aorta with branches labelled. Image description available.\" width=\"380\" height=\"359\"> <a id=\"Figure9.8\" href=\"\"><\/a>Figure 9.8. Arteries of the Thoracic and Abdominal Regions The thoracic aorta gives rise to the arteries of the visceral and parietal branches. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.8id\">[Image description.]<\/a>[\/caption]<\/figure>\nPeople who smoke or have [pb_glossary id=\"250\"]hypertension[\/pb_glossary], [pb_glossary id=\"407\"]hypercholesterolemia[\/pb_glossary], and\/or [pb_glossary id=\"403\"]atherosclerosis[\/pb_glossary] have an increased risk of developing aneurysms. Having a family history of aneurysms or certain genetic diseases may also increase a person's risk of developing an aneurysm.\n\nAneurysms can be asymptomatic and may be detected during diagnostic tests that are done for other reasons. They are sometimes repaired surgically and sometimes treated with medications such as [pb_glossary id=\"389\"]antihypertensives[\/pb_glossary] (Centers for Disease Control and Prevention, n.d.-c; National Heart, Lung, and Blood Institute, n.d.). Visit the <a href=\"https:\/\/www.nhlbi.nih.gov\/health-topics\/aneurysm\">National Heart, Lung, and Blood Institute's web page on aortic aneurysms<\/a> to learn more.\n<h3>Heart Defects<\/h3>\n<p id=\"fs-id2587120\">Fetal circulation is different from [pb_glossary id=\"627\"]postnatal[\/pb_glossary] circulation. There are two extra openings in the fetal heart, the [pb_glossary id=\"387\"]foramen ovale[\/pb_glossary] and the [pb_glossary id=\"388\"]ductus arteriosus[\/pb_glossary], which allow blood circulation that bypasses the immature fetal lungs. The fetal blood is reoxygenated by the mother's lungs and transported between mother and fetus via the placenta. These two openings usually close around the time of birth.<\/p>\nSeptal defects are commonly first detected through [pb_glossary id=\"244\"]auscultation[\/pb_glossary]. Unusual heart sounds may be detected because blood is not flowing and valves are not closing correctly. Medical imaging is ordered to confirm or rule out a diagnosis. In many cases, treatment may not be needed.\n<ul>\n \t<li id=\"fs-id1546810\"><strong>Patent ductus arteriosus<\/strong> is a congenital condition in which the ductus arteriosus fails to close. If untreated, the condition can result in congestive heart failure.<\/li>\n \t<li><strong>Patent foramen ovale <\/strong>is one type of atrial septal defect (ASD), due to a failure of the hole in the [pb_glossary id=\"386\"]interatrial septum[\/pb_glossary] to close at birth.\n<ul>\n \t<li>As much as 20 to 25% of the general population may have a patent foramen ovale. Most have the benign, asymptomatic version but in extreme cases, a surgical repair is required to close the opening permanently.<\/li>\n<\/ul>\n<\/li>\n \t<li><strong>Tetralogy of Fallot<\/strong> is a congenital condition that may also occur from exposure to unknown environmental factors; it occurs when there is an opening in the [pb_glossary id=\"401\"]interventricular septum[\/pb_glossary] caused by blockage of the pulmonary trunk, normally at the pulmonary semilunar valve. This allows blood that is relatively low in oxygen from the right ventricle to flow into the left ventricle and mix with the blood that is relatively high in oxygen.\n<ul>\n \t<li>Signs and symptoms include a distinct heart murmur, low blood oxygen percent saturation, [pb_glossary id=\"295\"]dyspnea[\/pb_glossary], [pb_glossary id=\"402\"]polycythemia[\/pb_glossary], clubbing of the fingers and toes, and in children, difficulty in feeding or failure to grow and develop.<\/li>\n \t<li>It is the most common cause of [pb_glossary id=\"246\"]cyanosis[\/pb_glossary] following birth. Other heart defects may also accompany this condition, which is typically confirmed by [pb_glossary id=\"247\"]echocardiography[\/pb_glossary] imaging.<\/li>\n<\/ul>\n<\/li>\n \t<li>In the case of severe septal defects, including both tetralogy of fallot and patent foramen ovale, failure of the heart to develop properly can lead to a condition commonly known as a<strong> blue baby.<\/strong> Regardless of normal skin pigmentation, individuals with this condition have an insufficient supply of oxygenated blood, which leads to [pb_glossary id=\"246\"]cyanosis[\/pb_glossary], especially when active.<\/li>\n<\/ul>\n[caption id=\"\" align=\"aligncenter\" width=\"655\"]<img src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2009_Congenital_Heart_Defects.jpg\" alt=\"This diagram shows the structure of the heart with different congenital defects. The top left panel shows patent foramen ovale, the top right panel shows coarctation of the aorta, the bottom left panel shows patent ductus ateriosus and the bottom right shows tetralogy of fallot.\" width=\"655\" height=\"397\"> <a id=\"Figure9.9\" href=\"\"><\/a>Figure 9.9. Congenital Heart Defects. (a) A patent foramen ovale defect is an abnormal opening in the interatrial septum, or more commonly, a failure of the foramen ovale to close. (b) Coarctation of the aorta is an abnormal narrowing of the aorta. (c) A patent ductus arteriosus is the failure of the ductus arteriosus to close. (d) Tetralogy of Fallot includes an abnormal opening in the interventricular septum. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.9id\">[Image description.]<\/a>[\/caption]\n<h2>Diseases Related to Coronary Circulation<\/h2>\n<h3>Coronary Artery Disease (CAD)<\/h3>\n<strong style=\"text-align: initial;font-size: 1em\">Coronary artery disease <\/strong><span style=\"text-align: initial;font-size: 1em\">occurs when the buildup of [pb_glossary id=\"404\"]plaque[\/pb_glossary] in the coronary arteries obstructs the flow of blood and decreases [pb_glossary id=\"400\"]compliance[\/pb_glossary] of the vessels. This condition is called [pb_glossary id=\"403\"]atherosclerosis[\/pb_glossary]. As the disease progresses and coronary blood vessels become more and more narrow, cells of the myocardium become [pb_glossary id=\"408\"]ischemic[\/pb_glossary] which causes symptoms of <\/span><span style=\"text-align: initial;font-size: 1em\">[pb_glossary id=\"406\"]angina pectoris[\/pb_glossary], in some patients. If untreated, coronary artery disease can lead to myocardial infarction (MI). <\/span>\n\n<span style=\"font-size: 1em;text-align: initial\">The image below shows the blockage of coronary arteries on an [pb_glossary id=\"405\"]angiogram[\/pb_glossary].<\/span>\n<figure id=\"fig-ch20_01_15\"><figcaption><\/figcaption>[caption id=\"\" align=\"aligncenter\" width=\"564\"]<img src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2016_Occluded_Coronay_Arteries.jpg\" alt=\"This photo shows a blockage in the coronary artery and in the circumflex artery.\" width=\"564\" height=\"564\"> <a id=\"Figure9.10\" href=\"\"><\/a>Figure 9.10. Angiogram of Atherosclerotic Coronary Arteries. In this coronary angiogram (X-ray), the dye makes visible two occluded coronary arteries. Such blockages can lead to decreased blood flow (ischemia) and insufficient oxygen (hypoxia) delivered to the cardiac tissues. If uncorrected, this can lead to cardiac muscle death (myocardial infarction). From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.10id\">[Image description.]<\/a>[\/caption]<\/figure>\n<p id=\"fs-id2046548\">CAD is progressive and chronic. Risk factors include smoking, family history, [pb_glossary id=\"250\"]hypertension[\/pb_glossary], obesity, diabetes, high alcohol consumption, lack of exercise, stress, and [pb_glossary id=\"249\"]hyperlipidemia[\/pb_glossary]. Treatments may include medication, changes to diet and exercise, angioplasty with a balloon catheter, insertion of a stent, or coronary artery bypass graft (CABG).<\/p>\n\n<ul>\n \t<li id=\"fs-id1263155\"><strong>Angioplasty<\/strong> is a procedure in which the [pb_glossary id=\"628\"]occlusion[\/pb_glossary] is mechanically widened with a balloon. A specialized catheter with an expandable tip is inserted into a blood vessel in the arm or leg, and then directed to the site of the occlusion. At this point, the balloon is inflated to compress the plaque material and to open the vessel to increase blood flow. Once the balloon is deflated and retracted, a stent consisting of a specialized mesh is typically inserted at the site of occlusion to reinforce the weakened and damaged walls and prevent re-occlusion.<\/li>\n \t<li><strong style=\"text-align: initial;font-size: 1em\">Coronary bypass surgery (Coronary artery bypass graft CABG)<\/strong><span style=\"text-align: initial;font-size: 1em\"> is a surgical procedure which grafts a replacement vessel obtained from another part of the body to bypass the occluded area. <\/span><\/li>\n<\/ul>\n<h3>Myocardial Infarction<\/h3>\n<section id=\"fs-id2717268\">\n<figure id=\"fig-ch20_01_04\"><\/figure>\n<\/section>\n<p id=\"fs-id1289761\"><strong>Myocardial infarction (MI)<\/strong> is the medical term for a heart attack.<\/p>\nA MI normally results from a lack of blood flow to a region of the heart, resulting in death of the cardiac muscle cells. A MI often occurs when a coronary artery is blocked by the buildup of atherosclerotic plaque. It can also occur when a piece of an atherosclerotic plaque breaks off and travels through the coronary arterial system until it lodges in one of the smaller vessels. MIs may be triggered by excessive exercise, in which the partially occluded artery is no longer able to pump sufficient quantities of blood, or severe stress, which may induce spasm of the smooth muscle in the walls of the vessel.\n<p id=\"fs-id2351428\">In the case of <strong>acute MI (AMI)<\/strong>, there is often sudden pain beneath the sternum (retrosternal pain) called angina pectoris, often radiating down the left arm in males but not in female patients. Other common signs and symptoms include [pb_glossary id=\"295\"]dyspnea[\/pb_glossary], [pb_glossary id=\"390\"]palpitations[\/pb_glossary], nausea and vomiting, [pb_glossary id=\"391\"]diaphoresis[\/pb_glossary], anxiety, and [pb_glossary id=\"392\"]syncope[\/pb_glossary]. Many of the symptoms are shared with other medical conditions, including anxiety attacks and simple indigestion, so differential diagnosis is critical.<\/p>\n<p id=\"fs-id2586043\">An MI can be confirmed by examining the patient's [pb_glossary id=\"481\"]ECG[\/pb_glossary].<\/p>\nOther diagnostic tests include:\n<ul>\n \t<li>[pb_glossary id=\"247\"]echocardiography[\/pb_glossary].<\/li>\n \t<li>[pb_glossary id=\"393\"]CT[\/pb_glossary].<\/li>\n \t<li>[pb_glossary id=\"394\"]MRI[\/pb_glossary].<\/li>\n \t<li>Common blood tests indicating an MI include elevated levels of [pb_glossary id=\"395\"]creatine kinase MB[\/pb_glossary] and [pb_glossary id=\"396\"]cardiac troponin[\/pb_glossary], both of which are released by damaged cardiac muscle cells.<\/li>\n<\/ul>\n<p id=\"fs-id2808942\">MIs may induce dangerous heart rhythms and even cardiac arrest. Important risk factors for MI include coronary artery disease, age, smoking, high blood levels of [pb_glossary id=\"397\"]LDL[\/pb_glossary], low levels of [pb_glossary id=\"398\"]HDL[\/pb_glossary], [pb_glossary id=\"250\"]hypertension[\/pb_glossary], [pb_glossary id=\"399\"]diabetes mellitus[\/pb_glossary], obesity, lack of physical exercise, chronic kidney disease, excessive alcohol consumption, and use of illegal drugs.<\/p>\n&nbsp;\n<div class=\"textbox textbox--key-takeaways\"><header class=\"textbox__header\">\n<h3 class=\"textbox__title\"><em>Did you know?<\/em><\/h3>\n<\/header>\n<div class=\"textbox__content\">\n\n<span class=\"tight\">It is estimated that between 22 and 64% of myocardial infarctions present without any symptoms.<\/span>\n\n<\/div>\n<\/div>\n<h2>Diseases of the (Electrical) Conduction System<\/h2>\n<h3>Arrhythmia<\/h3>\nThe heart's natural pacemaker, the sinoatrial (SA) node initiates an electrical impulse 60 to 90 times per minute in a resting adult. This impulse travels through the heart's conduction system in order to ensure a smooth, coordinated pumping action. This electrical activity can be detected and recorded through the skin using an [pb_glossary id=\"276\"]electrocardiograph[\/pb_glossary]. [pb_glossary id=\"411\"]Arrhythmias[\/pb_glossary] may occur when the SA node fails to initiate an impulse, or when the conduction system fails to transmit that impulse through the heart.\n\nIn the event that the electrical activity of the heart is severely disrupted, cessation of electrical activity or fibrillation may occur. In fibrillation, the heart beats in a wild, uncontrolled manner, which prevents it from being able to pump effectively.\n<ul>\n \t<li><strong>Atrial fibrillation<\/strong> is a serious condition, but as long as the ventricles continue to pump blood, the patient\u2019s life may not be in immediate danger.<\/li>\n \t<li><b>Ventricular fibrillation<\/b> is a medical emergency that requires life support, because the ventricles are not effectively pumping blood, left untreated ventricular fibrillation may lead to brain death.<\/li>\n<\/ul>\nThe most common treatment is <strong>defibrillation<\/strong> which uses special paddles to apply a charge to the heart from an external electrical source in an attempt to establish a normal sinus rhythm. A defibrillator effectively stops the heart so that the SA node can trigger a normal conduction cycle. <strong>External automated defibrillators (EADs<\/strong>) are being placed in areas frequented by large numbers of people, such as schools, restaurants, and airports. These devices contain simple and direct verbal instructions that can be followed by non-medical personnel in an attempt to save a life.\n\n&nbsp;\n<div class=\"textbox textbox--key-takeaways\"><header class=\"textbox__header\">\n<h3 class=\"textbox__title\"><em>Did you know?<\/em><\/h3>\n<\/header>\n<div class=\"textbox__content\">\n\nArrhythmia does <em>not<\/em> mean an absence of a heartbeat. That would be asystole, or flat line. Arrhythmia is defined as the absence of a <em>regular<\/em> rhythm, meaning that the heart rate is either too fast, too slow or just irregular.\n\n<\/div>\n<\/div>\n<h3 id=\"fs-id1775301\">Abnormal Heart Rates<\/h3>\n<strong>Bradycardia<\/strong> is the condition in which resting adult heart rate drops below 60 beats per minute (bpm). A client exhibiting signs and symptoms such as weakness, fatigue, dizziness, [pb_glossary id=\"392\"]syncope[\/pb_glossary], chest discomfort, palpitations, or respiratory distress may indicate that the heart is not providing sufficient oxygenated blood to the tissues. If the patient is not exhibiting symptoms then bradycardia is not considered clinically significant. The term <strong>relative bradycardia<\/strong> may be used with a patient who has a heart rate in the normal range but is still suffering from these symptoms. Most patients remain asymptomatic as long as the heart rate remains above 50 bpm.\n\n<strong> Tachycardia<\/strong> is the condition in which the resting rate is above 100 bpm. Tachycardia is not normal in a resting patient and may be detected in pregnant women or individuals experiencing extreme stress. Some individuals may remain [pb_glossary id=\"258\"]asymptomatic[\/pb_glossary], but when present, signs and symptoms may include dizziness, shortness of breath, rapid pulse, heart palpitations, chest pain, or syncope. Treatment depends upon the underlying cause but may include medications, [pb_glossary id=\"466\"]ablation[\/pb_glossary], [pb_glossary id=\"465\"] implantable cardioverter defibrillators[\/pb_glossary], or surgery.\n<h3>Heart Block<\/h3>\n<p id=\"fs-id2059534\">A <strong>heart block<\/strong> refers to an interruption in the normal conduction pathway. Heart blocks are generally named after the part of the conduction system that is causing the problem. For example, bundle branch blocks occur within either the left or right atrioventricular bundle branches.<\/p>\n<p id=\"fs-id1856568\">[pb_glossary id=\"412\"]AV[\/pb_glossary] blocks are often described by degrees. A <strong>first-degree or partial block<\/strong> indicates a delay in conduction between the SA and AV nodes. A <strong>second-degree or incomplete block<\/strong> occurs when some impulses from the SA node reach the AV node and continue, while others do not. In the <strong>third-degree or complete block<\/strong>, there is no correlation between atrial activity and ventricular activity. This means that none of the impulses generated by the SA node get transmitted to the rest of the heart and the AV node must take over as the primary pacemaker, initiating contractions at 40 to 60 bpm, which is adequate to maintain consciousness.<\/p>\n<p id=\"fs-id1499991\">In order to speed up the heart rate and restore full [pb_glossary id=\"413\"]sinus rhythm[\/pb_glossary], a cardiologist can implant an <strong>artificial pacemaker<\/strong>, which delivers electrical impulses to the heart muscle to ensure that the heart continues to contract and pump blood effectively. These artificial pacemakers are programmable by the cardiologists and can either provide stimulation temporarily upon demand or on a continuous basis. Some devices also contain built-in defibrillators.<\/p>\n\n[caption id=\"\" align=\"aligncenter\" width=\"779\"]<img src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2024_Cardiac_Arrhythmias.jpg\" alt=\"In this image the QT cycle for different heart conditions are shown. From top to bottom, the arrhythmias shown are second-degree partial block, atrial fibrillation, ventricular tachycardia, ventricular fibrillation and third degree block.\" width=\"779\" height=\"798\"> <a id=\"Figure9.11\" href=\"\"><\/a>Figure 9.11. Common ECG Abnormalities. (a) In a second-degree or partial block, one-half of the P waves are not followed by the QRS complex and T waves while the other half are. (b) In atrial fibrillation, the electrical pattern is abnormal prior to the QRS complex, and the frequency between the QRS complexes has increased. (c) In ventricular tachycardia, the shape of the QRS complex is abnormal. (d) In ventricular fibrillation, there is no normal electrical activity. (e) In a third-degree block, there is no correlation between atrial activity (the P wave) and ventricular activity (the QRS complex). From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.11id\">[Image description.]<\/a>[\/caption]\n<h2>Medical Terms in Context<\/h2>\n[h5p id=\"54\"]\n<h2>Medical Specialties Related to the Cardiovascular System<\/h2>\n<h3>Cardiologists and Thoracic Surgeons<\/h3>\nCardiologists are medical doctors that specialize in diagnosing and treating heart diseases. After completing medical school, cardiologists must complete at least six more years of training (Betts et al., 2013). Thoracic surgeons provide surgical treatments on the heart and other thoracic organs (National Cancer Institute, n.d.). For more information, visit the <a href=\"https:\/\/www.cardiosmart.org\/topics\/manage-your-care\/what-is-a-cardiologist\">American College of Cardiology Foundation's web page on cardiologists<\/a>.\n<h3>Cardiology Technologists<\/h3>\nCardiology technologists complete a college training program and perform diagnostic tests such as [pb_glossary id=\"277\"]electrocardiography[\/pb_glossary] and stress testing, as well as [pb_glossary id=\"464\"]pacemaker[\/pb_glossary] monitoring (Bureau of Labor Statistics, 2021). Please visit the <a href=\"https:\/\/www.bls.gov\/ooh\/healthcare\/diagnostic-medical-sonographers.htm\">Bureau of Labor Statistics' web page on cardiology technologists<\/a> for more information.\n<h3>Cardiovascular Perfusionists<\/h3>\nCardiovascular perfusionists complete a college training program and are responsible for operation of the heart-lung bypass machine during open heart surgery. They also monitor the patient's vitals and administer medications (New York State Education Department, 2020). For more information, please read <a href=\"http:\/\/www.abcp.org\/pd\/jobs.pdf\">this job description from the American Board of Cardiovascular Perfusion (PDF)<\/a>.\n<h2>Cardiovascular System Vocabulary<\/h2>\n<strong>Ablation <\/strong>\n\nThe removal or destruction of a body part or tissue or its function. Ablation may be performed by surgery, hormones, drugs, radiofrequency, heat, or other methods.\n\n<strong>Aneurysm<\/strong>\n\nWeakening of the wall of a blood vessel, causing it to thin and balloon out, and possibly eventually burst, resulting in internal bleeding.\n\n<strong>Angina pectoris <\/strong>\n\nChest pain. It may be a symptom of coronary artery disease and myocardial infarction.\n\n<strong>Angiogram<\/strong>\n\nAn x-ray or computer image (CT scan or MRI) of the blood vessels and blood flow in the body. A dye may be injected through a catheter (small tube) into an artery or vein to make the blood vessels easier to see.\n\n<strong>Antihypertensives <\/strong>\n\nA class of medications used to treat high blood pressure.\n\n<strong>Arrhythmia<\/strong>\n\nA deviation from the normal pattern of impulse conduction and contraction of the heart.\n\n<strong>Asymptomatic<\/strong>\n\nHaving no signs or symptoms of disease.\n\n<strong>Atherosclerosis<\/strong>\n\nA hardening of the arteries that involves the accumulation of plaque.\n\n<strong>Auscultation<\/strong>\n\nListening to the heart using a stethoscope.\n\n<strong>Atrioventricular (AV)<\/strong>\n\nThe area of the heart where the atria and ventricles meet.\n\n<strong>Atrioventricular (AV) valves<\/strong>\n\nMitral (bicuspid) valve that allows blood to flow from left atrium to left ventricle and tricuspid valve that allows blood to flow from right atrium to right ventricle.\n\n<strong>Bradycardia<\/strong>\n\nA condition in which the heart beats slower than 50 beats per minute.\n\n<strong>Cardiac<\/strong>\n\nHaving to do with the heart.\n\n<strong>Cardiac troponin<\/strong>\n\nThe regulatory protein for muscle contraction.\n\n<strong>Cardiogenic<\/strong>\n\nOriginating from the heart.\n\n<strong>Cardiologist<\/strong>\n\nA physician who studies and treats diseases of the heart.\n\n<strong>Cardiology<\/strong>\n\nThe study of the heart.\n\n<strong>Cardiomegaly<\/strong>\n\nEnlarged heart.\n\n<strong>Cardiomyopathy<\/strong>\n\nDisease of the heart muscle.\n\n<strong>Compliance<\/strong>\n\nThe ability of the blood vessels to dilate and constrict as needed.\n\n<strong>Computerized tomography (CT)<\/strong>\n\nA noninvasive imaging technique that uses computers to analyze several cross-sectional X-rays in order to reveal minute details about structures in the body.\n\n<strong>Congenital<\/strong>\n\nPresent at birth.\n\n<strong>Creatine kinase MB<\/strong>\n\nAn enzyme that catalyzes the conversion of creatine to phosphocreatine, consuming ATP.\n\n<strong>Cyanosis <\/strong>\n\nA condition in which the oxygen supply is restricted, causing the skin to look blue.\n\n<strong>Diabetes mellitus<\/strong>\n\nA disease in which the body does not control the amount of glucose (a type of sugar) in the blood and the kidneys make a large amount of urine. This disease occurs when the body does not make enough insulin or does not use it the way it should.\n\n<strong>Diaphoresis<\/strong>\n\nSweating.\n\n<strong>Diastole<\/strong>\n\nPeriod of time when the heart muscle is relaxed and the chambers fill with blood.\n\n<strong>Ductus arteriosus<\/strong>\n\nA temporary connection between pulmonary trunk and aorta in the fetal heart.\n\n<strong>Dyspnea<\/strong>\n\nDifficulty breathing.\n\n<strong>Echocardiogram<\/strong>\n\nA computer picture of the heart created by bouncing high-energy sound waves (ultrasound) off internal tissues or organs of the chest.\n\n<strong>Echocardiography<\/strong>\n\nA procedure that uses high-energy sound waves (ultrasound) to look at tissues and organs inside the chest.\n\n<strong>Electrocardiogram (ECG\/EKG)<\/strong>\n\nThe record of the heart's function produced by the electrocardiograph.\n\n<strong>Electrocardiograph<\/strong>\n\nThe instrument that generates an electrocardiogram (ECG); 10 electrodes are placed in standard locations on the patient's skin to record heart function.\n\n<strong>Electrocardiography<\/strong>\n\nThe science of recording the electrical activity of the heart.\n\n<strong>Endocarditis<\/strong>\n\nA condition in which the tissues lining the inside of the heart and the heart valves become inflamed.\n\n<strong>Foramen ovale <\/strong>\n\nAn opening between right and left atria, which is normal in the fetal heart.\n\n<strong>Great vessels <\/strong>\n\nInclude the superior vena cava, inferior vena cava, aorta and pulmonary trunk.\n\n<strong>Heart murmur<\/strong>\n\nAn abnormal heart sound.\n\n<strong>Heart rate<\/strong>\n\nThe number of times the heart beats within a certain time period, usually a minute.\n\n<strong>High-density lipoprotein (HDL)<\/strong>\n\nOften referred to as \"good\" cholesterol.\n\n<strong>Hypercholesterolemia <\/strong>\n\nHigher than normal levels of cholesterol in the blood.\n\n<strong>Hyperlipidemia <\/strong>\n\nExcessive fat in the blood.\n\n<strong>Hypertension <\/strong>\n\nAbnormally high blood pressure.\n\n<strong>Implantable cardioverter defibrillators (ICD)<\/strong>\n\nA small device placed by surgery in the chest or abdomen that is used to correct a heartbeat that is abnormal. Wires are passed through a vein to connect the device to the heart. When it detects abnormal heartbeats, it sends an electrical shock to the heart to restore the heartbeat to normal.\n\n<strong>Inferior vena cava<\/strong>\n\nOne of the two largest veins in the body. It carries deoxygenated blood from the torso and legs back to the heart.\n\n<strong>Interatrial septum<\/strong>\n\nThe wall separating the right and left atria.\n\n<strong>Interventricular septum<\/strong>\n\nThe wall of myocardium that separates the right and left ventricles.\n\n<strong>Ischemia<\/strong>\n\nLack of blood flow to body tissues.\n\n<strong>Low-density lipoprotein (LDL)<\/strong>\n\nOften referred to as 'bad' cholesterol.\n\n<strong>Magnetic Resonance Imaging (MRI)<\/strong>\n\nA procedure in which radio waves and a powerful magnet linked to a computer are used to create detailed pictures of areas inside the body.\n\n<strong>Mitral valve <\/strong>\n\nLocated at the opening between the left atrium and left ventricle; also known as the bicuspid valve.\n\n<strong>Myocardial infarction (MI)<\/strong>\n\nHeart attack, caused by lack of blood flow and oxygen to the heart.\n\n<strong>Myocarditis<\/strong>\n\nA rare condition in which the heart muscle becomes thick and inflamed and may also become weak.\n\n<strong>Occlusion<\/strong>\n\nA blockage.\n\n<strong>Pacemaker<\/strong>\n\nAn electronic device that is implanted in the body to monitor heart rate and rhythm. It gives the heart electrical stimulation when it does not beat normally.\n\n<strong>Palpitations<\/strong>\n\nA rapid or irregular heartbeat that a person can feel.\n\n<strong>Pericardial fluid<\/strong>\n\nWatery fluid produced in the serous and visceral pericardium surrounding the surface of the heart.\n\n<strong>Pericarditis<\/strong>\n\nInflammation of the (sac) surrounding the heart.\n\n<strong>Pericardiocentesis<\/strong>\n\nSurgical puncture to aspirate fluid from the (sac) surrounding the heart.\n\n<strong>Plaque<\/strong>\n\nA fatty material including cholesterol, connective tissue, white blood cells, and some smooth muscle cells.\n\n<strong>Polycythemia<\/strong>\n\nA rare disorder in which the bone marrow produces an abnormally large amount of blood cells.\n\n<strong>Pulmonary trunk <\/strong>\n\nThe very large artery referred to as a trunk, a term indicating that the vessel gives rise to several smaller arteries.\n\n<strong>Roots of the great vessels<\/strong>\n\nThe part of each great vessel (aorta, pulmonary trunk, inferior vena cava, superior vena cava) that connects to the base of the heart.\n\n<strong>Serous membrane<\/strong>\n\nOne of the thin membranes that cover the walls and organs in the thoracic and abdominopelvic cavities.\n\n<strong>Sinus rhythm<\/strong>\n\nThe normal electrical pattern followed by contraction of the heart.\n\n<strong>Sphygmomanometer<\/strong>\n\nA blood pressure cuff attached to a measuring device.\n\n<strong>Stethoscope<\/strong>\n\nAn instrument used to hear sounds produced by the heart, lungs, or other parts of the body.\n\n<strong>Superior vena cava<\/strong>\n\nOne of two large veins in the body, which carries deoxygenated blood from the head and upper extremities back to the heart.\n\n<strong>Syncope<\/strong>\n\nFainting.\n\n<strong>Systole<\/strong>\n\nPeriod of time when the heart muscle is contracting.\n\n<strong>Tachycardia<\/strong>\n\nA condition in which the resting rate is above 100 bpm.\n\n<strong>Valvuloplasty<\/strong>\n\nThe widening of a stenosed heart valve using a balloon catheter.\n<h2>Test Yourself<\/h2>\n[h5p id=\"55\"]\n\n&nbsp;\n<h2>References<\/h2>\nBureau of Labor Statistics. (2021). Medical sonographers and cardiovascular technologists and technicians. In <em>Occupational outlook handbook<\/em>. U.S. Department of Labor. <a href=\"https:\/\/www.bls.gov\/ooh\/healthcare\/diagnostic-medical-sonographers.htm\">https:\/\/www.bls.gov\/ooh\/healthcare\/diagnostic-medical-sonographers.htm <\/a>\n\nCenters for Disease Control and Prevention. (n.d.-a). <em>Cardiomyopathy<\/em>. CDC. <a href=\"https:\/\/www.cdc.gov\/heartdisease\/cardiomyopathy.htm\">https:\/\/www.cdc.gov\/heartdisease\/cardiomyopathy.htm<\/a>\n\nCenters for Disease Control and Prevention. (n.d.-b). <em>Valvular heart disease<\/em>. CDC. <a href=\"https:\/\/www.cdc.gov\/heartdisease\/valvular_disease.htm\">https:\/\/www.cdc.gov\/heartdisease\/valvular_disease.htm<\/a>\n\nCenters for Disease Control and Prevention. (n.d.-c). <em>Aortic aneurysm<\/em>. CDC. <a href=\"https:\/\/www.cdc.gov\/heartdisease\/aortic_aneurysm.htm\">https:\/\/www.cdc.gov\/heartdisease\/aortic_aneurysm.htm<\/a>\n\nCrashCourse. (2015, July 6). <em>The heart, part 1 - under pressure: Crash course A&amp;P #25 <\/em>[Video]. YouTube. <a href=\"https:\/\/youtu.be\/X9ZZ6tcxArI\">https:\/\/youtu.be\/X9ZZ6tcxArI<\/a>\n\nCrashCourse. (2015, July 13). <em>The heart, part 2 - heart throbs: Crash course A&amp;P #26<\/em> [Video]. YouTube. <a href=\"https:\/\/youtu.be\/FLBMwcvOaEo\">https:\/\/youtu.be\/FLBMwcvOaEo<\/a>\n\nNational Heart, Lung, and Blood Institute. (n.d.). <em>Aortic aneurysm<\/em>. National Institutes of Health, U.S. Department of Health and Human Services. <a href=\"https:\/\/www.nhlbi.nih.gov\/health-topics\/aneurysm\">https:\/\/www.nhlbi.nih.gov\/health-topics\/aneurysm<\/a>\n\nNational Cancer Institute. (n.d.). <em>Definition of thoracic surgeon. <\/em>National Institutes of Health, U.S. Department of Health and Human Services.. <a href=\"https:\/\/www.cancer.gov\/publications\/dictionaries\/cancer-terms\/def\/thoracic-surgeon\">https:\/\/www.cancer.gov\/publications\/dictionaries\/cancer-terms\/def\/thoracic-surgeon<\/a>\n\nNew York State Education Department. (2020). <em>Perfusionist<\/em>. Retrieved November 1, 2021, from <a href=\"http:\/\/www.op.nysed.gov\/careers\/perfprofile.htm\">http:\/\/www.op.nysed.gov\/careers\/perfprofile.htm<\/a>\n<h2>Image Descriptions<\/h2>\n<a id=\"Figure9.1id\" href=\"\"><\/a><strong>Figure 9.1 image description:<\/strong> This diagram shows the location of the heart in the thorax (sagittal and anterior views). The sagittal view labels read (from top, clockwise): first rib, aortic arch, thoracic arch, esophagus, inferior vena cava, diaphragm, thymus, trachea. The anterior view labels read (from top, clockwise): mediastinum, arch of aorta, pulmonary trunk, left auricle, left lung, left ventricle, pericardial cavity, apex of heart, edge of parietal pericardium, diaphragm, edge of parietal pleura, ribs, right ventricle, right atrium, right auricle, right lung, superior vena cava. <a href=\"#Figure9.1\">[Return to Figure 9.1].<\/a>\n\n<a id=\"Figure9.2id\" href=\"\"><\/a><strong>Figure 9.2 image description:<\/strong> This image shows a magnified view of the structure of the heart wall. Labels read (from top, clockwise): pericardial cavity, fibrous pericardium, parietal layer of serous pericardium, epicardium (visceral layer of serous pericardium), myocardium, endocardium. <a href=\"#Figure9.2\">[Return to Figure 9.2].<\/a>\n\n<a id=\"Figure9.3id\" href=\"\"><\/a><strong>Figure 9.3 image description:<\/strong> This diagram shows the network of blood vessels in the lungs. Labels read (from top, clockwise (left-side of the body): aortic arch, pulmonary trunk, left lung, left pulmonary arteries, left pulmonary vein, pulmonary capillaries, descending aorta, (right side of body) inferior vena cava, right pulmonary veins, right pulmonary arteries, right lung, superior vena cava, ascending aorta. <a href=\"#Figure9.3\">[Return to Figure 9.3].<\/a>\n\n<a id=\"Figure9.4id\" href=\"\"><\/a><strong>Figure 9.4 image description:<\/strong> The top panel shows the human heart with the arteries and veins labeled (from top, clockwise): aorta, left pulmonary arteries, pulmonary trunk, left atrium, left pulmonary veins, aortic semilunar valve, mitral valve, left ventricle, inferior vena cava, right ventricle, tricuspid valve, right atrium, pulmonary semilunar valve, right pulmonary veins, right pulmonary arteries, superior vena cava. The bottom panel shows a rough map of the human circulatory system. Labels read (from top, clockwise): systemic capillaries of upper body, systemic arteries to upper body, pulmonary trunk, left atrium, left ventricle, systemic arteries to lower body, systemic capillaries of lower body, systemic veins from lower body, right ventricle, right atrium, pulmonary capillaries in lungs, systemic veins from upper body. <a href=\"#Figure9.4\">[Return to Figure 9.4].<\/a>\n\n<a id=\"Figure9.5id\" href=\"\"><\/a><strong>Figure 9.5 image description:<\/strong> The top panel of this figure shows the anterior view of the heart while the bottom panel shows the posterior view of the heart. The different blood vessels are labeled. Anterior view labels (from top of diagram, clockwise): left coronary artery, pulmonary trunk, circumflex artery, anterior interventricular artery, great cardiac vein, small cardiac vein, anterior cardiac veins, atrial arteries, right atrium, right coronary artery, ascending aorta, aortic arch. Posterior view labels (from top of diagram, clockwise): coronary sinus, small cardiac vein, right coronary artery, marginal artery, middle cardiac vein, posterior cardiac vein, posterior interventricular artery, marginal artery, great cardiac vein, circumflex artery. <a href=\"#Figure9.5\">[Return to Figure 9.5].<\/a>\n\n<a id=\"Figure9.6id\" href=\"\"><\/a><strong>Figure 9.6 image description:<\/strong> This image shows the anterior view of the frontal section of the heart with the major parts labeled. Labels read (from top of diagram, clockwise) arch of aorta, Bachman's bundle, atrioventricular bundle (bundle of His), left ventricle, right and left bundle branches, Purkinje fibers, right ventricle, right atrium, posterior intermodal, middle intermodal, atrioventricular node, anterior intermodal, Sinoatrial node. <a href=\"#Figure9.6\">[Return to Figure 9.6].<\/a>\n\n<a id=\"Figure9.7id\" href=\"\"><\/a><strong>Figure 9.7 image description:<\/strong> This diagram shows the six different stages of heart contraction and relaxation along with the stages in the QT cycle. <a href=\"#Figure9.7\">[Return to Figure 9.7].<\/a>\n\n<a id=\"Figure9.8id\" href=\"\"><\/a><strong>Figure 9.8 image description:<\/strong> This diagram shows the arteries in the thoracic and abdominal cavity. Visceral branches of the thoracic aorta labels (from top): bronchial, esophageal, mediastinal, pericardial, thoracic aorta, aortic hiatus, celiac trunk, left gastric, splenic, common hepatic, superior mesenteric, abdominal aorta, inferior mesenteric, external iliac. Parietal (somatic) branches of thoracic aorta labels (from top): intercostal, superior phrenic, inferior phrenic, diaphragm, adrenal, renal, gonadal, lumbar, medial sacral, common iliac, internal iliac. <a href=\"#Figure9.8\">[Return to Figure 9.8].<\/a>\n\n<a id=\"Figure9.9id\" href=\"\"><\/a><strong>Figure 9.9 image description:<\/strong> This diagram shows the structure of the heart with different congenital defects. The top left panel shows patent foramen ovale (label reads foramen ovale fails to close), the top right panel shows coarctation of the aorta (label reads narrow segment of aorta), the bottom left panel shows patent ductus arteriosus (label reads Ductus arteriosus remains open) and the bottom right shows tetralogy of fallot (labels read aorta emerges from both ventricles, interventricular septal defect, enlarged right ventricle, stenosed pulmonary semilunar valve). <a href=\"#Figure9.9\">[Return to Figure 9.9].<\/a>\n\n<strong><a id=\"Figure9.10id\" href=\"\"><\/a>Figure <\/strong><strong>9.10 image description:<\/strong> An angiogram of atherosclerotic coronary arteries. The image shows blockages in the common trunk of the left coronary artery and circumflex artery. Blockages can cause ischemia, hypoxia, and myocardial infarction. <a href=\"\u201c#Figure9.10&quot;\">[Return to Figure 9.10].<\/a>\n\n<a id=\"Figure9.11id\" href=\"\"><\/a><strong>Figure 9.11 image description:<\/strong> In this image the QT cycle for different heart conditions are shown. From top to bottom, the arrhythmias shown are second-degree partial blocks (text reads: Note how half of the P waves are not followed by the QRS complex and T waves while the other half are. Question: what would you expect to happen to heart rate?), atrial fibrillation (text reads: Note the abnormal electric pattern prior to the QRS complexes. Also note how the frequency between the QRS complexes has increased. Question: What would you expect to happen to heart rate?), ventricular tachycardia (text reads: Note the unusual shape of the QRS complex, focusing on the S component. Question: What would you expect to happen to heart rate?), ventricular fibrillation (text reads: Note the total lack of normal electrical activity. Question: What would you expect to happen to heart rate?), and third degree block (text reads: Note that in a third-degree block some of the impulses initiated by the SA node do not reach the AV node while others do. Also note that the P waves are not followed by the QRS complex. Question: What would you expect to happen to heart rate?). <a href=\"#Figure9.11\">[Return to Figure 9.11].<\/a>\n<div class=\"textbox shaded\">Unless otherwise indicated, this chapter contains material adapted from <a href=\"https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/1-introduction\"><em>Anatomy and Physiology<\/em><\/a> (on <a href=\"https:\/\/openstax.org\/\">OpenStax<\/a>), by Betts et al. and is used under a <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0 international license<\/a>. Download and access this book for free at <a href=\"https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/1-introduction\">https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/1-introduction<\/a>.<\/div>\n&nbsp;","rendered":"<div class=\"textbox textbox--learning-objectives\">\n<header class=\"textbox__header\">\n<h3 class=\"textbox__title\"><em>Learning Objectives<\/em><\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n<li>Examine the anatomy of the heart<\/li>\n<li>Determine the main functions of the cardiovascular system<\/li>\n<li>Differentiate cardiovascular system medical terms and common abbreviations<\/li>\n<li>Recognize the medical specialties associated with the cardiovascular system<\/li>\n<li>Discover common diseases, disorders, and procedures related to the cardiovascular system<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<h2>Cardiovascular System Word Parts<\/h2>\n<p>Click on prefixes, combining forms, and suffixes to reveal a list of word parts to memorize for the cardiovascular system.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"h5p-49\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-49\" class=\"h5p-iframe\" data-content-id=\"49\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Cardiovascular System: Heart Word Parts\"><\/iframe><\/div>\n<\/div>\n<h2>Introduction to the Cardiovascular System<\/h2>\n<p id=\"fs-id1894016\">The cardiovascular system is made of three components: the heart, vessels, and blood. The heart is a fist-sized vital organ that has <em>one<\/em> job: to pump blood. If one assumes an average <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_369\">heart rate<\/a> of 75 beats per minute, a human heart would beat approximately 108,000 times in one day, more than 39 million times in one year, and nearly 3 billion times during a 75-year lifespan. At rest, each of the major pumping chambers of the heart ejects approximately 70 mL of blood per contraction in an adult. This would be equal to 5.25 liters of blood per minute and approximately 14,000 liters per day. Over one year, that would equal 10,000,000 liters of blood sent through roughly 100,000 km of blood vessels. In order to understand how that happens, it is necessary to understand the anatomy and physiology of the heart.<\/p>\n<h3>Watch this video:<\/h3>\n<div class=\"textbox shaded\">\n<p><iframe loading=\"lazy\" id=\"oembed-1\" title=\"The Heart, Part 1 - Under Pressure: Crash Course Anatomy &amp; Physiology #25\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/X9ZZ6tcxArI?start=2&#38;feature=oembed\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<p><em>Media 9.1. <a href=\"https:\/\/youtu.be\/X9ZZ6tcxArI\">The Heart, Part 1 &#8211; Under Pressure: Crash Course A&amp;P #25<\/a> [Online video]. Copyright 2015 by <a href=\"https:\/\/www.youtube.com\/channel\/UCX6b17PVsYBQ0ip5gyeme-Q\">CrashCourse<\/a>.<\/em><\/p>\n<\/div>\n<h2 id=\"fs-id2281225\">Practice Medical Terms Related to the Cardiovascular System<\/h2>\n<section>\n<div id=\"h5p-50\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-50\" class=\"h5p-iframe\" data-content-id=\"50\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Cardiovascular System: Medical Terms\"><\/iframe><\/div>\n<\/div>\n<h2>Anatomy of the Heart<\/h2>\n<h3 id=\"fs-id1892589\">Location<\/h3>\n<p>The human heart is located within the thoracic cavity, between the lungs in the space known as the <strong>mediastinum<\/strong>. <a href=\"#Figure9.1\">Figure 9.1<\/a> shows the position of the heart within the thoracic cavity. Within the mediastinum, the heart is separated from the other mediastinal structures by a tough membrane known as the pericardium, or pericardial sac, and sits in its own space called the <strong>pericardial cavity<\/strong>. The <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_370\">great vessels<\/a>, which carry blood to and from the heart, are attached to the superior surface of the heart, which is called the base. The base of the heart is located at the level of the third costal cartilage. The inferior tip of the heart, the apex, lies just to the left of the sternum between the junction of the fourth and fifth ribs.<\/p>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<h3 class=\"textbox__title\">Concept Check<\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n<li>On the diagram below (Figure 1), locate the <strong>mediastinum<\/strong>, the <strong>pericardial cavity<\/strong>, the <strong>base<\/strong> of the heart and the <strong>apex<\/strong> of the heart.<\/li>\n<li>Locate the largest vein in the body, the <strong>superior vena cava<\/strong>.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<figure id=\"fig-ch20_01_01\"><figcaption><\/figcaption><figure style=\"width: 666px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2001_Heart_Position_in_ThoraxN.jpg\" alt=\"Location of the heart in the thorax. Image description available.\" width=\"666\" height=\"605\" \/><figcaption class=\"wp-caption-text\"><a id=\"Figure9.1\" href=\"\"><\/a>Figure 9.1. Position of the Heart in the Thorax. The heart is located within the thoracic cavity, medially between the lungs in the mediastinum. It is about the size of a fist, is broad at the top, and tapers toward the base. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.1id\">[Image description.]<\/a><\/figcaption><\/figure>\n<\/figure>\n<\/section>\n<section id=\"fs-id3028596\">\n<h3 id=\"fs-id2959986\">Membranes and Layers of the Heart Walls<\/h3>\n<p>The heart and the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_373\">roots of the great vessels<\/a> are surrounded by a membrane known as the <strong>pericardium<\/strong> or <strong>pericardial sac<\/strong>. The pericardium consists of two distinct sub layers:<\/p>\n<ul>\n<li>The sturdy outer fibrous pericardium is made of tough, dense connective tissue that protects the heart and holds it in position.<\/li>\n<li>Separated by the <strong>pericardial<\/strong> <strong>cavity <\/strong>and containing pericardial fluid the inner <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_372\">serous<\/a> pericardium consists of two layers:\n<ul>\n<li>the outer <strong>parietal pericardium<\/strong>, which is fused to the fibrous pericardium.<\/li>\n<li>the inner <strong>visceral pericardium<\/strong>, or <strong>epicardium<\/strong>, which is fused to the heart and forms the outer layer of the heart wall.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p id=\"fs-id2418328\">The walls of the heart consist of three layers:<\/p>\n<ul>\n<li>The outer <strong>epicardium<\/strong>, which is another name for the visceral pericardium mentioned above.<\/li>\n<li>The thick, middle <strong>myocardium<\/strong>, which is made of muscle tissue and gives the heart its ability to contract.<\/li>\n<li>The inner <strong>endocardium<\/strong>, which lines the heart chambers and is the main component of the heart valves.<\/li>\n<\/ul>\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<h3 class=\"textbox__title\">Concept Check<\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n<li>Look at <a href=\"#Figure9.2\">Figure 9.2<\/a> below, and name the layers of the heart wall and surrounding membranes, starting with the innermost layer.<\/li>\n<li>As shown on the diagram, suggest why the <strong>myocardium<\/strong> layer is thicker than the <strong>endocardium<\/strong> layer.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<figure id=\"fig-ch20_01_04\">\n<figure style=\"width: 627px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2004_Heart_Wall.jpg\" alt=\"Magnified view of the heart's wall. Image description available.\" width=\"627\" height=\"435\" \/><figcaption class=\"wp-caption-text\"><a id=\"Figure9.2\" href=\"\"><\/a>Figure 9.2. Pericardial Membranes and Layers of the Heart Wall. The pericardial membrane that surrounds the heart consists of three layers and the pericardial cavity. The heart wall also consists of three layers. The pericardial membrane and the heart wall share the epicardium From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.2id\">[Image description.]<\/a><\/figcaption><\/figure>\n<\/figure>\n<h3>Internal Structures of the Heart<\/h3>\n<p>The heart consists of four chambers:<\/p>\n<ul>\n<li>The upper chambers are the right and left <strong>atria<\/strong> (singular: atrium).<\/li>\n<li>The lower chambers are the right and left <strong>ventricles.<\/strong><\/li>\n<\/ul>\n<p>The <strong>interventricular septum<\/strong> is a muscular wall that separates the right and left ventricles. The interatrial septum separates the right and left atria.<\/p>\n<p>The atrium and ventricle on each side of the heart are separated by an atrioventricular (AV) valve:<\/p>\n<ul>\n<li>The right AV valve, or <strong>tricuspid valve,<\/strong> separates the right atrium and right ventricle.<\/li>\n<li>The left AV valve, or <strong>bicuspid valve, <\/strong>separates the left ventricle and the left atrium. This valve is also called the <strong>mitral valve.<\/strong><\/li>\n<\/ul>\n<p>There are also two semilunar valves:<\/p>\n<ul>\n<li>The <strong>pulmonary valve<\/strong> separates the right ventricle from the pulmonary trunk.<\/li>\n<li>The <strong>aortic valve<\/strong> separates the left ventricle from the aorta.<\/li>\n<\/ul>\n<h2>Anatomy Labeling Activity<\/h2>\n<div id=\"h5p-51\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-51\" class=\"h5p-iframe\" data-content-id=\"51\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Cardiovascular System: The Heart Anatomy\"><\/iframe><\/div>\n<\/div>\n<\/section>\n<h2>Physiology of the Heart<\/h2>\n<section id=\"fs-id1987886\">In order for the heart to do its job of pumping blood to the lungs and the body, nutrients and oxygen must be supplied to the cells of the heart. The heart also needs to coordinate its contractions so that all parts are working together to pump blood effectively. To understand how all of this works together to give the heart its ability to pump blood, we will examine three interdependent aspects of heart function.<\/p>\n<ol>\n<li>Circulation through the heart: Blood is pumped by the heart in order to provide oxygen and nutrients to every cell in the body.<\/li>\n<li>The heart as an organ (coronary blood supply): The heart is an organ, made of cells and tissues which require their own blood supply.<\/li>\n<li>The heart&#8217;s electrical conduction system: The heart is able to independently generate and transmit instructions to the myocardium in order to make it contract and pump the blood.<\/li>\n<\/ol>\n<h3>1. Circulation Through the Heart: The Heart as a Pump<\/h3>\n<p id=\"fs-id2767147\">The heart pumps blood to two distinct but linked circulatory systems called the pulmonary and systemic circuits. The <strong>pulmonary circuit<\/strong> transports blood to and from the lungs, where it picks up oxygen and drops off carbon dioxide. The <strong>systemic circuit<\/strong> transports freshly oxygenated blood to virtually all of the tissues of the body and returns relatively deoxygenated blood and carbon dioxide to the heart to be sent back to the pulmonary circulation.<\/p>\n<ol>\n<li>Blood that is carrying carbon dioxide and waste products from the body tissues is returned to the <strong>right atrium<\/strong> via the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_375\">superior vena cava<\/a> and the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_376\">inferior vena cava<\/a>.<\/li>\n<li>From the right atrium, the deoxygenated blood moves through the <strong>tricuspid valve<\/strong> into the right ventricle.<\/li>\n<li>The <strong>right ventricle<\/strong> pumps deoxygenated blood through the <strong>pulmonary valve<\/strong> into the <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_421\">pulmonary trunk<\/a><\/strong>, which splits into the <strong>right and left pulmonary arteries<\/strong>, leading toward the lungs. These arteries branch many times before reaching the <strong>pulmonary capillaries<\/strong>, where gas exchange occurs: carbon dioxide exits the blood, and oxygen enters. The pulmonary arteries are the only arteries in the postnatal body that carries deoxygenated blood. Did you notice that they are often colored blue on diagrams of the heart?<\/li>\n<li>Freshly oxygenated blood returns from the lungs to the <strong>left atrium<\/strong> via the <strong>pulmonary veins<\/strong>. These veins are the only postnatal veins in the body that carry highly oxygenated blood and are often colored red on heart images.<\/li>\n<li>From the left atrium, the blood moves through the <strong>mitral valve<\/strong> into the <strong>left ventricle. <\/strong><\/li>\n<li>The left ventricle pumps blood through the <strong>aortic valve<\/strong>, into the <strong>aorta<\/strong>, delivering blood to all parts of the body.<\/li>\n<\/ol>\n<\/section>\n<div class=\"textbox textbox--key-takeaways\">\n<header class=\"textbox__header\">\n<h3 class=\"textbox__title\"><em>Did you know?<\/em><\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<p><span class=\"tight\">The heart sounds heard through a stethoscope are the sounds of the four heart valves opening and closing at specific times during one cardiac cycle.<\/span><\/p>\n<\/div>\n<\/div>\n<section>\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<h3 class=\"textbox__title\">Concept Check<\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n<li>On <a href=\"#Figure9.3\">Figure 9.3<\/a> below, use your finger to trace the pathway of blood flowing through the right side of the heart, naming each of the following structures as you encounter them: Superior and inferior venae cavae, right atrium, tricuspid valve, right ventricle, pulmonary valve, right and left pulmonary arteries.<\/li>\n<li>Suggest what would happen if the <strong>aorta<\/strong> experienced a blockage or constriction.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/section>\n<figure id=\"fig-ch20_01_03\">\n<figure id=\"attachment_92\" aria-describedby=\"caption-attachment-92\" style=\"width: 692px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-92\" src=\"https:\/\/pressbooks.ccconline.org\/accphysicalgeology\/wp-content\/uploads\/sites\/228\/2019\/09\/22489f4ba975acba9cff1daae384b2cacb46705a-1024x590.jpg\" alt=\"\" width=\"692\" height=\"398\" srcset=\"https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-content\/uploads\/sites\/228\/2019\/09\/22489f4ba975acba9cff1daae384b2cacb46705a-1024x590.jpg 1024w, https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-content\/uploads\/sites\/228\/2019\/09\/22489f4ba975acba9cff1daae384b2cacb46705a-300x173.jpg 300w, https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-content\/uploads\/sites\/228\/2019\/09\/22489f4ba975acba9cff1daae384b2cacb46705a-768x442.jpg 768w, https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-content\/uploads\/sites\/228\/2019\/09\/22489f4ba975acba9cff1daae384b2cacb46705a-65x37.jpg 65w, https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-content\/uploads\/sites\/228\/2019\/09\/22489f4ba975acba9cff1daae384b2cacb46705a-225x130.jpg 225w, https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-content\/uploads\/sites\/228\/2019\/09\/22489f4ba975acba9cff1daae384b2cacb46705a-350x202.jpg 350w, https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-content\/uploads\/sites\/228\/2019\/09\/22489f4ba975acba9cff1daae384b2cacb46705a.jpg 1507w\" sizes=\"auto, (max-width: 692px) 100vw, 692px\" \/><figcaption id=\"caption-attachment-92\" class=\"wp-caption-text\"><a id=\"Figure9.3\" href=\"\"><\/a>Figure 9.3. Pulmonary Circuit Blood exiting from the right ventricle flows into the pulmonary trunk, which bifurcates into the two pulmonary arteries. These vessels branch to supply blood to the pulmonary capillaries, where gas exchange occurs within the lung alveoli. Blood returns via the pulmonary veins to the left atrium. From Betts et al., 2013. Licensed under CC BY 4.0. [<a href=\"#Figure9.3id\">Image description<\/a>.]<\/figcaption><\/figure>\n<h4>Pulmonary Circuit<\/h4>\n<p>Blood exiting from the right ventricle flows into the pulmonary trunk, which bifurcates into the two pulmonary arteries. These vessels branch to supply blood to the pulmonary capillaries, where gas exchange occurs within the lung alveoli. Blood returns via the pulmonary veins to the left atrium.<\/p>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<h3 class=\"textbox__title\">Concept Check<\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<p>On <a href=\"#Figure9.4\">Figure 9.4<\/a> below, use your finger to trace the pathway of blood flowing through the left side of the heart, naming each of the following structures as you encounter them: right and left pulmonary veins, left atrium, mitral valve, left ventricle, aortic valve, aorta.<\/p>\n<\/div>\n<\/div>\n<figure style=\"width: 775px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2003_Dual_System_of_Human_Circulation.jpg\" alt=\"Diagram of heart and circulatory system showing direction of blood flow. Image description available.\" width=\"775\" height=\"855\" \/><figcaption class=\"wp-caption-text\"><a id=\"Figure9.4\" href=\"\"><\/a>Figure 9.4. Dual System of the Human Blood Circulation. Blood flows from the right atrium to the right ventricle, where it is pumped into the pulmonary circuit. The blood in the pulmonary artery branches is low in oxygen but relatively high in carbon dioxide. Gas exchange occurs in the pulmonary capillaries (oxygen into the blood, carbon dioxide out), and blood high in oxygen and low in carbon dioxide is returned to the left atrium. From here, blood enters the left ventricle, which pumps it into the systemic circuit. Following the exchange in the systemic capillaries (oxygen and nutrients out of the capillaries and carbon dioxide and wastes in), blood returns to the right atrium and the cycle is repeated. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.4id\">[Image description.]<\/a><\/figcaption><\/figure>\n<h4>Cardiac Cycle<\/h4>\n<p>The process of pumping and circulating blood is active, coordinated, and rhythmic. Each heartbeat represents one cycle of the heart receiving blood and ejecting blood.<\/p>\n<ul>\n<li><strong>Diastole<\/strong> is the portion of the cycle in which the heart is relaxed and the atria and ventricles are filling with blood. The AV valves are open so that blood can move from the atria to the ventricles.<\/li>\n<li><strong style=\"text-align: initial;font-size: 1em\">Systole<\/strong><span style=\"text-align: initial;font-size: 1em\"> is the portion of the cycle in which the heart contracts, AV valves slam shut, and the ventricles eject blood to the lungs and the body through the open semilunar valves. Once this phase ends, the semilunar valves close, in preparation for another filling phase.<\/span><\/li>\n<\/ul>\n<h3>2. The Heart as an Organ: The Coronary Blood Supply<\/h3>\n<p>Myocardial cells require their own blood supply to carry out their function of contracting and relaxing the heart in order to pump blood. Their own blood supply provides nutrients and oxygen and carries away carbon dioxide and waste. These functions are provided by the coronary arteries and coronary veins.<\/p>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<h3 class=\"textbox__title\">Concept Check<\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<p>On the <a href=\"#Figure9.5\">image<\/a> below, locate the three main coronary arteries:<\/p>\n<ul>\n<li><strong>Anterior interventricular artery<\/strong> (more commonly known as the <strong>left anterior descending artery, or LAD<\/strong>)<\/li>\n<li><strong>Circumflex artery (Cx)<\/strong><\/li>\n<li><strong>Right coronary artery (RCA)<\/strong><\/li>\n<\/ul>\n<p>Follow the path of each of these three arteries to try to determine which parts of the myocardium each artery (along with its many smaller branches) supplies with blood.<\/p>\n<\/div>\n<\/div>\n<figure style=\"width: 678px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"\" src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2014ab_Coronary_Blood_Vessels.jpg\" alt=\"Anterior and posterior views of the heart and its blood vessels. Image description available.\" width=\"678\" height=\"623\" \/><figcaption class=\"wp-caption-text\"><a id=\"Figure9.5\" href=\"\"><\/a>Figure 9.5 Coronary Circulation. The anterior view of the heart shows the prominent coronary surface vessels. The posterior view of the heart shows the prominent coronary surface vessels. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.5id\">[Image description.]<\/a><\/figcaption><\/figure>\n<h3>3. The Heart&#8217;s Electrical Conduction System<\/h3>\n<p>In order for all parts of the heart to work together to beat regularly and effectively, the heart has its own electrical system, which initiates and conducts each heartbeat through the entire myocardium. Specialized groups of heart cells perform this function all on their own, without requiring messages from the central nervous system.<\/figure>\n<h4>Watch this video:<\/h4>\n<div class=\"textbox shaded\">\n<p><iframe loading=\"lazy\" id=\"oembed-2\" title=\"The Heart, Part 2 - Heart Throbs: Crash Course Anatomy &amp; Physiology #26\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/FLBMwcvOaEo?feature=oembed&#38;rel=0&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<p><em>Media 9.2. <a href=\"https:\/\/youtu.be\/FLBMwcvOaEo\">The Heart, Part 2 &#8211; Heart Throbs: Crash Course A&amp;P #26<\/a> [Online video]. Copyright 2015 by <a href=\"https:\/\/www.youtube.com\/channel\/UCX6b17PVsYBQ0ip5gyeme-Q\">CrashCourse<\/a>.<\/em><\/p>\n<\/div>\n<figure style=\"width: 805px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"\" src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2018_Conduction_System_of_Heart.jpg\" alt=\"Anterior view of frontal section of the heart. Image description available.\" width=\"805\" height=\"540\" \/><figcaption class=\"wp-caption-text\"><a id=\"Figure9.6\" href=\"\"><\/a>Figure 9.6. Conduction System of the Heart. Specialized conducting components of the heart include the sinoatrial node, the internodal pathways, the atrioventricular node, the atrioventricular bundle, the right and left bundle branches, and the Purkinje fibers. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.6id\">[Image description.]<\/a><\/figcaption><\/figure>\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<h3 class=\"textbox__title\">Concept Check<\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<p>On the <a href=\"#Figure9.6\">image<\/a> above, trace the electrical impulse generated by the heart&#8217;s pacemaker (the <strong>sinoatrial node<\/strong>, or <strong>SA node<\/strong>) through the rest of the conduction system, including the <strong>atrioventricular (AV) node<\/strong>, the <strong>atrioventricular bundle (bundle of His)<\/strong>, the <strong>right and left bundle branches<\/strong>, and the <strong>Purkinje fibers<\/strong>.<\/p>\n<\/div>\n<\/div>\n<p>We can detect and record the electrical activity of the heart&#8217;s conduction system using an electrocardiogram (ECG or EKG). <a href=\"#Figure9.7\">Figure 9.7<\/a> shows the electrical impulse originating in the SA node (step 2) and traveling through the heart&#8217;s conduction system, allowing the heart to complete one cardiac cycle. Each waveform on the ECG tracing represents electricity moving through and affecting a different part of the heart. Did you notice that the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_410\">AV valves<\/a> close when the electrical impulse reaches the ventricles, just before systole occurs?<\/p>\n<figure style=\"width: 2206px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2023_ECG_Tracing_with_Heart_ContractionN.jpg\" alt=\"ECG tracing correlated to the cardiac cycle. Image description available.\" width=\"2206\" height=\"1613\" \/><figcaption class=\"wp-caption-text\"><a id=\"Figure9.7\" href=\"\"><\/a>Figure 9.7. ECG Tracing Correlated to the Cardiac Cycle. This diagram correlates an ECG tracing with the electrical and mechanical events of a heart contraction. Each segment of an ECG tracing corresponds to one event in the cardiac cycle. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.7id\">[Image description.]<\/a><\/figcaption><\/figure>\n<h2>Practice Terms Related to the Cardiovascular System<\/h2>\n<div id=\"h5p-52\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-52\" class=\"h5p-iframe\" data-content-id=\"52\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Cardiovascular System: Terms not easily broken down into word parts\"><\/iframe><\/div>\n<\/div>\n<h2>Common Abbreviations for the Cardiovascular System<\/h2>\n<p>Many terms and phrases related to the cardiovascular system are abbreviated. Learn these common abbreviations by expanding the list below.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"h5p-53\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-53\" class=\"h5p-iframe\" data-content-id=\"53\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Cardiovascular System: Abbreviations\"><\/iframe><\/div>\n<\/div>\n<h2>Diseases and Disorders of the Heart<\/h2>\n<h3>Cardiomyopathy<\/h3>\n<p>The heart of a well-trained athlete can be considerably larger than the average person&#8217;s heart. This is because exercise results in an increase in muscle cells called <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_289\">hypertrophy<\/a>. Hearts of athletes can pump blood more effectively at lower rates than those of non-athletes. However, when an enlarged heart is not the result of exercise, it may be due to <strong>hypertrophic cardiomyopathy<\/strong>. The cause of an abnormally enlarged heart muscle is unknown, but the condition is often undiagnosed and can cause sudden death in apparently otherwise healthy young people.<\/p>\n<p>Other types of cardiomyopathy include:<\/p>\n<ul>\n<li><strong>Dilated cardiomyopathy<\/strong>, which also has an unknown cause and is seen in people of any age. In this disorder, one of the ventricles of the heart is larger than normal.<\/li>\n<li><strong>Arrhythmogenic cardiomyopathy<\/strong>, an inherited condition that results in irregular heart rhythms.<\/li>\n<li><strong>Restrictive cardiomyopathy<\/strong>, which is a complication of other conditions which cause the myocardium to scar or stiffen (Centers for Disease Control and Prevention, 2019).<\/li>\n<\/ul>\n<p>Cardiomyopathy may also be caused by myocardial infarctions, myocardial infections, pregnancy, alcohol or cocaine abuse, autoimmune and endocrine diseases. Because the myocardium is responsible for contracting and pumping blood, patients with cardiomyopathy experience impaired heart function which may lead to heart failure (Centers for Disease Control and Prevention, n.d.-a). To learn more, visit the <a href=\"https:\/\/www.cdc.gov\/heartdisease\/cardiomyopathy.htm\">Centers for Disease Control and Prevention&#8217;s web page on cardiomyopathy.<\/a><\/p>\n<h3 id=\"fig-ch20_01_08\">Heart Failure<\/h3>\n<p><strong>Heart failure<\/strong> is defined as the inability of the heart to pump enough blood to meet the needs of the body. It is also called <strong>congestive heart failure (CHF). <\/strong>This condition causes swelling in the lower extremities and shortness of breath, due to a buildup of fluid in the lungs. It may be caused by cardiomyopathy, and it may lead to <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_250\">hypertension<\/a> and heart valve disorders (Heart &amp; Stroke, n.d.). To learn more, visit the <a href=\"https:\/\/www.heart.org\/en\/health-topics\/heart-failure\/what-is-heart-failure\">American Heart Association&#8217;s web page on heart failure<\/a>.<\/p>\n<h3>Valvular Heart Disease<\/h3>\n<p>The four heart valves open and close at specific times during the cardiac cycle, in order to ensure that blood flows in only one direction through the heart. This requires that these valves open and close completely. Infections such as rheumatic disease or bacterial endocarditis can affect the heart valves and result in scar tissue formation which interferes with valve function. Other causes of heart valve disease include congenitally malformed valves, autoimmune diseases, and other cardiovascular diseases such as aortic aneurysms and atherosclerosis (Centers for Disease Control and Prevention, n.d.-b).<\/p>\n<p>Heart valve disease may be <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_258\">asymptomatic<\/a> or cause <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_295\">dyspnea<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_411\">arrhythmias<\/a>, fatigue and other symptoms. It is often detected when a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_385\">heart murmur<\/a> is heard through a stethoscope (Centers for Disease Control and Prevention, n.d.-b).<\/p>\n<ul>\n<li><strong>Mitral Valve <\/strong><b>Prolapse<\/b>\n<ul>\n<li>The mitral (bicuspid) valve is diseased or malformed and is not able to close completely, allowing the regurgitation of blood back into the left atrium during systole. Because some of the blood goes back into the atrium, insufficient blood is pumped out of the ventricle into the systemic circulation. This inability to close properly and the resulting regurgitation may also be found in other heart valves (Centers for Disease Control and Prevention, n.d.-b).<\/li>\n<\/ul>\n<\/li>\n<li><strong>Aortic Stenosis<\/strong>\n<ul>\n<li>The aortic valve is narrowed and hardened, preventing it from opening fully and allowing sufficient blood to travel to the systemic circulation. Any heart valve can be stenosed, but this disorder most often affects the aortic valve (Centers for Disease Control and Prevention, n.d.-b).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>Visit the <a href=\"https:\/\/www.cdc.gov\/heartdisease\/valvular_disease.htm\">Center for Disease Control and Prevention&#8217;s web page on valvular heart disease<\/a> to learn more.<\/p>\n<h3>Aneurysms<\/h3>\n<p>An aneurysm is a defect in the wall of an artery in which the wall becomes thin and weak and starts to balloon out as blood pulses against the vessel wall. This can happen to any artery and even to the myocardial walls. Aneurysms sometimes occur in the portion of the aorta that is in the thorax (see <a href=\"#Figure9.8\">Figure 9.8<\/a>). If these aneurysms start to leak between layers of the vessel wall, the condition is known as aortic dissection. If an aortic or cardiac aneurysm bursts, there is sudden, massive internal bleeding (Centers for Disease Control and Prevention, n.d.-c).<\/p>\n<figure>\n<figure style=\"width: 380px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2124_Thoracic_Abdominal_Arteries.jpg\" alt=\"Thoracic aorta with branches labelled. Image description available.\" width=\"380\" height=\"359\" \/><figcaption class=\"wp-caption-text\"><a id=\"Figure9.8\" href=\"\"><\/a>Figure 9.8. Arteries of the Thoracic and Abdominal Regions The thoracic aorta gives rise to the arteries of the visceral and parietal branches. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.8id\">[Image description.]<\/a><\/figcaption><\/figure>\n<\/figure>\n<p>People who smoke or have <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_250\">hypertension<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_407\">hypercholesterolemia<\/a>, and\/or <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_403\">atherosclerosis<\/a> have an increased risk of developing aneurysms. Having a family history of aneurysms or certain genetic diseases may also increase a person&#8217;s risk of developing an aneurysm.<\/p>\n<p>Aneurysms can be asymptomatic and may be detected during diagnostic tests that are done for other reasons. They are sometimes repaired surgically and sometimes treated with medications such as <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_389\">antihypertensives<\/a> (Centers for Disease Control and Prevention, n.d.-c; National Heart, Lung, and Blood Institute, n.d.). Visit the <a href=\"https:\/\/www.nhlbi.nih.gov\/health-topics\/aneurysm\">National Heart, Lung, and Blood Institute&#8217;s web page on aortic aneurysms<\/a> to learn more.<\/p>\n<h3>Heart Defects<\/h3>\n<p id=\"fs-id2587120\">Fetal circulation is different from <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_627\">postnatal<\/a> circulation. There are two extra openings in the fetal heart, the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_387\">foramen ovale<\/a> and the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_388\">ductus arteriosus<\/a>, which allow blood circulation that bypasses the immature fetal lungs. The fetal blood is reoxygenated by the mother&#8217;s lungs and transported between mother and fetus via the placenta. These two openings usually close around the time of birth.<\/p>\n<p>Septal defects are commonly first detected through <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_244\">auscultation<\/a>. Unusual heart sounds may be detected because blood is not flowing and valves are not closing correctly. Medical imaging is ordered to confirm or rule out a diagnosis. In many cases, treatment may not be needed.<\/p>\n<ul>\n<li id=\"fs-id1546810\"><strong>Patent ductus arteriosus<\/strong> is a congenital condition in which the ductus arteriosus fails to close. If untreated, the condition can result in congestive heart failure.<\/li>\n<li><strong>Patent foramen ovale <\/strong>is one type of atrial septal defect (ASD), due to a failure of the hole in the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_386\">interatrial septum<\/a> to close at birth.\n<ul>\n<li>As much as 20 to 25% of the general population may have a patent foramen ovale. Most have the benign, asymptomatic version but in extreme cases, a surgical repair is required to close the opening permanently.<\/li>\n<\/ul>\n<\/li>\n<li><strong>Tetralogy of Fallot<\/strong> is a congenital condition that may also occur from exposure to unknown environmental factors; it occurs when there is an opening in the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_401\">interventricular septum<\/a> caused by blockage of the pulmonary trunk, normally at the pulmonary semilunar valve. This allows blood that is relatively low in oxygen from the right ventricle to flow into the left ventricle and mix with the blood that is relatively high in oxygen.\n<ul>\n<li>Signs and symptoms include a distinct heart murmur, low blood oxygen percent saturation, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_295\">dyspnea<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_402\">polycythemia<\/a>, clubbing of the fingers and toes, and in children, difficulty in feeding or failure to grow and develop.<\/li>\n<li>It is the most common cause of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_246\">cyanosis<\/a> following birth. Other heart defects may also accompany this condition, which is typically confirmed by <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_247\">echocardiography<\/a> imaging.<\/li>\n<\/ul>\n<\/li>\n<li>In the case of severe septal defects, including both tetralogy of fallot and patent foramen ovale, failure of the heart to develop properly can lead to a condition commonly known as a<strong> blue baby.<\/strong> Regardless of normal skin pigmentation, individuals with this condition have an insufficient supply of oxygenated blood, which leads to <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_246\">cyanosis<\/a>, especially when active.<\/li>\n<\/ul>\n<figure style=\"width: 655px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2009_Congenital_Heart_Defects.jpg\" alt=\"This diagram shows the structure of the heart with different congenital defects. The top left panel shows patent foramen ovale, the top right panel shows coarctation of the aorta, the bottom left panel shows patent ductus ateriosus and the bottom right shows tetralogy of fallot.\" width=\"655\" height=\"397\" \/><figcaption class=\"wp-caption-text\"><a id=\"Figure9.9\" href=\"\"><\/a>Figure 9.9. Congenital Heart Defects. (a) A patent foramen ovale defect is an abnormal opening in the interatrial septum, or more commonly, a failure of the foramen ovale to close. (b) Coarctation of the aorta is an abnormal narrowing of the aorta. (c) A patent ductus arteriosus is the failure of the ductus arteriosus to close. (d) Tetralogy of Fallot includes an abnormal opening in the interventricular septum. From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.9id\">[Image description.]<\/a><\/figcaption><\/figure>\n<h2>Diseases Related to Coronary Circulation<\/h2>\n<h3>Coronary Artery Disease (CAD)<\/h3>\n<p><strong style=\"text-align: initial;font-size: 1em\">Coronary artery disease <\/strong><span style=\"text-align: initial;font-size: 1em\">occurs when the buildup of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_404\">plaque<\/a> in the coronary arteries obstructs the flow of blood and decreases <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_400\">compliance<\/a> of the vessels. This condition is called <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_403\">atherosclerosis<\/a>. As the disease progresses and coronary blood vessels become more and more narrow, cells of the myocardium become <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_408\">ischemic<\/a> which causes symptoms of <\/span><span style=\"text-align: initial;font-size: 1em\"><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_406\">angina pectoris<\/a>, in some patients. If untreated, coronary artery disease can lead to myocardial infarction (MI). <\/span><\/p>\n<p><span style=\"font-size: 1em;text-align: initial\">The image below shows the blockage of coronary arteries on an <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_405\">angiogram<\/a>.<\/span><\/p>\n<figure id=\"fig-ch20_01_15\"><figcaption><\/figcaption><figure style=\"width: 564px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2016_Occluded_Coronay_Arteries.jpg\" alt=\"This photo shows a blockage in the coronary artery and in the circumflex artery.\" width=\"564\" height=\"564\" \/><figcaption class=\"wp-caption-text\"><a id=\"Figure9.10\" href=\"\"><\/a>Figure 9.10. Angiogram of Atherosclerotic Coronary Arteries. In this coronary angiogram (X-ray), the dye makes visible two occluded coronary arteries. Such blockages can lead to decreased blood flow (ischemia) and insufficient oxygen (hypoxia) delivered to the cardiac tissues. If uncorrected, this can lead to cardiac muscle death (myocardial infarction). From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.10id\">[Image description.]<\/a><\/figcaption><\/figure>\n<\/figure>\n<p id=\"fs-id2046548\">CAD is progressive and chronic. Risk factors include smoking, family history, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_250\">hypertension<\/a>, obesity, diabetes, high alcohol consumption, lack of exercise, stress, and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_249\">hyperlipidemia<\/a>. Treatments may include medication, changes to diet and exercise, angioplasty with a balloon catheter, insertion of a stent, or coronary artery bypass graft (CABG).<\/p>\n<ul>\n<li id=\"fs-id1263155\"><strong>Angioplasty<\/strong> is a procedure in which the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_628\">occlusion<\/a> is mechanically widened with a balloon. A specialized catheter with an expandable tip is inserted into a blood vessel in the arm or leg, and then directed to the site of the occlusion. At this point, the balloon is inflated to compress the plaque material and to open the vessel to increase blood flow. Once the balloon is deflated and retracted, a stent consisting of a specialized mesh is typically inserted at the site of occlusion to reinforce the weakened and damaged walls and prevent re-occlusion.<\/li>\n<li><strong style=\"text-align: initial;font-size: 1em\">Coronary bypass surgery (Coronary artery bypass graft CABG)<\/strong><span style=\"text-align: initial;font-size: 1em\"> is a surgical procedure which grafts a replacement vessel obtained from another part of the body to bypass the occluded area. <\/span><\/li>\n<\/ul>\n<h3>Myocardial Infarction<\/h3>\n<section id=\"fs-id2717268\">\n<figure><\/figure>\n<\/section>\n<p id=\"fs-id1289761\"><strong>Myocardial infarction (MI)<\/strong> is the medical term for a heart attack.<\/p>\n<p>A MI normally results from a lack of blood flow to a region of the heart, resulting in death of the cardiac muscle cells. A MI often occurs when a coronary artery is blocked by the buildup of atherosclerotic plaque. It can also occur when a piece of an atherosclerotic plaque breaks off and travels through the coronary arterial system until it lodges in one of the smaller vessels. MIs may be triggered by excessive exercise, in which the partially occluded artery is no longer able to pump sufficient quantities of blood, or severe stress, which may induce spasm of the smooth muscle in the walls of the vessel.<\/p>\n<p id=\"fs-id2351428\">In the case of <strong>acute MI (AMI)<\/strong>, there is often sudden pain beneath the sternum (retrosternal pain) called angina pectoris, often radiating down the left arm in males but not in female patients. Other common signs and symptoms include <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_295\">dyspnea<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_390\">palpitations<\/a>, nausea and vomiting, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_391\">diaphoresis<\/a>, anxiety, and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_392\">syncope<\/a>. Many of the symptoms are shared with other medical conditions, including anxiety attacks and simple indigestion, so differential diagnosis is critical.<\/p>\n<p id=\"fs-id2586043\">An MI can be confirmed by examining the patient&#8217;s <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_481\">ECG<\/a>.<\/p>\n<p>Other diagnostic tests include:<\/p>\n<ul>\n<li><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_247\">echocardiography<\/a>.<\/li>\n<li><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_393\">CT<\/a>.<\/li>\n<li><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_394\">MRI<\/a>.<\/li>\n<li>Common blood tests indicating an MI include elevated levels of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_395\">creatine kinase MB<\/a> and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_396\">cardiac troponin<\/a>, both of which are released by damaged cardiac muscle cells.<\/li>\n<\/ul>\n<p id=\"fs-id2808942\">MIs may induce dangerous heart rhythms and even cardiac arrest. Important risk factors for MI include coronary artery disease, age, smoking, high blood levels of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_397\">LDL<\/a>, low levels of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_398\">HDL<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_250\">hypertension<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_399\">diabetes mellitus<\/a>, obesity, lack of physical exercise, chronic kidney disease, excessive alcohol consumption, and use of illegal drugs.<\/p>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--key-takeaways\">\n<header class=\"textbox__header\">\n<h3 class=\"textbox__title\"><em>Did you know?<\/em><\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<p><span class=\"tight\">It is estimated that between 22 and 64% of myocardial infarctions present without any symptoms.<\/span><\/p>\n<\/div>\n<\/div>\n<h2>Diseases of the (Electrical) Conduction System<\/h2>\n<h3>Arrhythmia<\/h3>\n<p>The heart&#8217;s natural pacemaker, the sinoatrial (SA) node initiates an electrical impulse 60 to 90 times per minute in a resting adult. This impulse travels through the heart&#8217;s conduction system in order to ensure a smooth, coordinated pumping action. This electrical activity can be detected and recorded through the skin using an <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_276\">electrocardiograph<\/a>. <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_411\">Arrhythmias<\/a> may occur when the SA node fails to initiate an impulse, or when the conduction system fails to transmit that impulse through the heart.<\/p>\n<p>In the event that the electrical activity of the heart is severely disrupted, cessation of electrical activity or fibrillation may occur. In fibrillation, the heart beats in a wild, uncontrolled manner, which prevents it from being able to pump effectively.<\/p>\n<ul>\n<li><strong>Atrial fibrillation<\/strong> is a serious condition, but as long as the ventricles continue to pump blood, the patient\u2019s life may not be in immediate danger.<\/li>\n<li><b>Ventricular fibrillation<\/b> is a medical emergency that requires life support, because the ventricles are not effectively pumping blood, left untreated ventricular fibrillation may lead to brain death.<\/li>\n<\/ul>\n<p>The most common treatment is <strong>defibrillation<\/strong> which uses special paddles to apply a charge to the heart from an external electrical source in an attempt to establish a normal sinus rhythm. A defibrillator effectively stops the heart so that the SA node can trigger a normal conduction cycle. <strong>External automated defibrillators (EADs<\/strong>) are being placed in areas frequented by large numbers of people, such as schools, restaurants, and airports. These devices contain simple and direct verbal instructions that can be followed by non-medical personnel in an attempt to save a life.<\/p>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--key-takeaways\">\n<header class=\"textbox__header\">\n<h3 class=\"textbox__title\"><em>Did you know?<\/em><\/h3>\n<\/header>\n<div class=\"textbox__content\">\n<p>Arrhythmia does <em>not<\/em> mean an absence of a heartbeat. That would be asystole, or flat line. Arrhythmia is defined as the absence of a <em>regular<\/em> rhythm, meaning that the heart rate is either too fast, too slow or just irregular.<\/p>\n<\/div>\n<\/div>\n<h3 id=\"fs-id1775301\">Abnormal Heart Rates<\/h3>\n<p><strong>Bradycardia<\/strong> is the condition in which resting adult heart rate drops below 60 beats per minute (bpm). A client exhibiting signs and symptoms such as weakness, fatigue, dizziness, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_392\">syncope<\/a>, chest discomfort, palpitations, or respiratory distress may indicate that the heart is not providing sufficient oxygenated blood to the tissues. If the patient is not exhibiting symptoms then bradycardia is not considered clinically significant. The term <strong>relative bradycardia<\/strong> may be used with a patient who has a heart rate in the normal range but is still suffering from these symptoms. Most patients remain asymptomatic as long as the heart rate remains above 50 bpm.<\/p>\n<p><strong> Tachycardia<\/strong> is the condition in which the resting rate is above 100 bpm. Tachycardia is not normal in a resting patient and may be detected in pregnant women or individuals experiencing extreme stress. Some individuals may remain <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_258\">asymptomatic<\/a>, but when present, signs and symptoms may include dizziness, shortness of breath, rapid pulse, heart palpitations, chest pain, or syncope. Treatment depends upon the underlying cause but may include medications, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_466\">ablation<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_465\"> implantable cardioverter defibrillators<\/a>, or surgery.<\/p>\n<h3>Heart Block<\/h3>\n<p id=\"fs-id2059534\">A <strong>heart block<\/strong> refers to an interruption in the normal conduction pathway. Heart blocks are generally named after the part of the conduction system that is causing the problem. For example, bundle branch blocks occur within either the left or right atrioventricular bundle branches.<\/p>\n<p id=\"fs-id1856568\"><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_412\">AV<\/a> blocks are often described by degrees. A <strong>first-degree or partial block<\/strong> indicates a delay in conduction between the SA and AV nodes. A <strong>second-degree or incomplete block<\/strong> occurs when some impulses from the SA node reach the AV node and continue, while others do not. In the <strong>third-degree or complete block<\/strong>, there is no correlation between atrial activity and ventricular activity. This means that none of the impulses generated by the SA node get transmitted to the rest of the heart and the AV node must take over as the primary pacemaker, initiating contractions at 40 to 60 bpm, which is adequate to maintain consciousness.<\/p>\n<p id=\"fs-id1499991\">In order to speed up the heart rate and restore full <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_413\">sinus rhythm<\/a>, a cardiologist can implant an <strong>artificial pacemaker<\/strong>, which delivers electrical impulses to the heart muscle to ensure that the heart continues to contract and pump blood effectively. These artificial pacemakers are programmable by the cardiologists and can either provide stimulation temporarily upon demand or on a continuous basis. Some devices also contain built-in defibrillators.<\/p>\n<figure style=\"width: 779px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/opentextbc.ca\/anatomyandphysiology\/wp-content\/uploads\/sites\/142\/2016\/03\/2024_Cardiac_Arrhythmias.jpg\" alt=\"In this image the QT cycle for different heart conditions are shown. From top to bottom, the arrhythmias shown are second-degree partial block, atrial fibrillation, ventricular tachycardia, ventricular fibrillation and third degree block.\" width=\"779\" height=\"798\" \/><figcaption class=\"wp-caption-text\"><a id=\"Figure9.11\" href=\"\"><\/a>Figure 9.11. Common ECG Abnormalities. (a) In a second-degree or partial block, one-half of the P waves are not followed by the QRS complex and T waves while the other half are. (b) In atrial fibrillation, the electrical pattern is abnormal prior to the QRS complex, and the frequency between the QRS complexes has increased. (c) In ventricular tachycardia, the shape of the QRS complex is abnormal. (d) In ventricular fibrillation, there is no normal electrical activity. (e) In a third-degree block, there is no correlation between atrial activity (the P wave) and ventricular activity (the QRS complex). From Betts et al., 2013. Licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0<\/a>. <a href=\"#Figure9.11id\">[Image description.]<\/a><\/figcaption><\/figure>\n<h2>Medical Terms in Context<\/h2>\n<div id=\"h5p-54\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-54\" class=\"h5p-iframe\" data-content-id=\"54\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Cardiovascular System: Consultation Report\"><\/iframe><\/div>\n<\/div>\n<h2>Medical Specialties Related to the Cardiovascular System<\/h2>\n<h3>Cardiologists and Thoracic Surgeons<\/h3>\n<p>Cardiologists are medical doctors that specialize in diagnosing and treating heart diseases. After completing medical school, cardiologists must complete at least six more years of training (Betts et al., 2013). Thoracic surgeons provide surgical treatments on the heart and other thoracic organs (National Cancer Institute, n.d.). For more information, visit the <a href=\"https:\/\/www.cardiosmart.org\/topics\/manage-your-care\/what-is-a-cardiologist\">American College of Cardiology Foundation&#8217;s web page on cardiologists<\/a>.<\/p>\n<h3>Cardiology Technologists<\/h3>\n<p>Cardiology technologists complete a college training program and perform diagnostic tests such as <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_277\">electrocardiography<\/a> and stress testing, as well as <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_93_464\">pacemaker<\/a> monitoring (Bureau of Labor Statistics, 2021). Please visit the <a href=\"https:\/\/www.bls.gov\/ooh\/healthcare\/diagnostic-medical-sonographers.htm\">Bureau of Labor Statistics&#8217; web page on cardiology technologists<\/a> for more information.<\/p>\n<h3>Cardiovascular Perfusionists<\/h3>\n<p>Cardiovascular perfusionists complete a college training program and are responsible for operation of the heart-lung bypass machine during open heart surgery. They also monitor the patient&#8217;s vitals and administer medications (New York State Education Department, 2020). For more information, please read <a href=\"http:\/\/www.abcp.org\/pd\/jobs.pdf\">this job description from the American Board of Cardiovascular Perfusion (PDF)<\/a>.<\/p>\n<h2>Cardiovascular System Vocabulary<\/h2>\n<p><strong>Ablation <\/strong><\/p>\n<p>The removal or destruction of a body part or tissue or its function. Ablation may be performed by surgery, hormones, drugs, radiofrequency, heat, or other methods.<\/p>\n<p><strong>Aneurysm<\/strong><\/p>\n<p>Weakening of the wall of a blood vessel, causing it to thin and balloon out, and possibly eventually burst, resulting in internal bleeding.<\/p>\n<p><strong>Angina pectoris <\/strong><\/p>\n<p>Chest pain. It may be a symptom of coronary artery disease and myocardial infarction.<\/p>\n<p><strong>Angiogram<\/strong><\/p>\n<p>An x-ray or computer image (CT scan or MRI) of the blood vessels and blood flow in the body. A dye may be injected through a catheter (small tube) into an artery or vein to make the blood vessels easier to see.<\/p>\n<p><strong>Antihypertensives <\/strong><\/p>\n<p>A class of medications used to treat high blood pressure.<\/p>\n<p><strong>Arrhythmia<\/strong><\/p>\n<p>A deviation from the normal pattern of impulse conduction and contraction of the heart.<\/p>\n<p><strong>Asymptomatic<\/strong><\/p>\n<p>Having no signs or symptoms of disease.<\/p>\n<p><strong>Atherosclerosis<\/strong><\/p>\n<p>A hardening of the arteries that involves the accumulation of plaque.<\/p>\n<p><strong>Auscultation<\/strong><\/p>\n<p>Listening to the heart using a stethoscope.<\/p>\n<p><strong>Atrioventricular (AV)<\/strong><\/p>\n<p>The area of the heart where the atria and ventricles meet.<\/p>\n<p><strong>Atrioventricular (AV) valves<\/strong><\/p>\n<p>Mitral (bicuspid) valve that allows blood to flow from left atrium to left ventricle and tricuspid valve that allows blood to flow from right atrium to right ventricle.<\/p>\n<p><strong>Bradycardia<\/strong><\/p>\n<p>A condition in which the heart beats slower than 50 beats per minute.<\/p>\n<p><strong>Cardiac<\/strong><\/p>\n<p>Having to do with the heart.<\/p>\n<p><strong>Cardiac troponin<\/strong><\/p>\n<p>The regulatory protein for muscle contraction.<\/p>\n<p><strong>Cardiogenic<\/strong><\/p>\n<p>Originating from the heart.<\/p>\n<p><strong>Cardiologist<\/strong><\/p>\n<p>A physician who studies and treats diseases of the heart.<\/p>\n<p><strong>Cardiology<\/strong><\/p>\n<p>The study of the heart.<\/p>\n<p><strong>Cardiomegaly<\/strong><\/p>\n<p>Enlarged heart.<\/p>\n<p><strong>Cardiomyopathy<\/strong><\/p>\n<p>Disease of the heart muscle.<\/p>\n<p><strong>Compliance<\/strong><\/p>\n<p>The ability of the blood vessels to dilate and constrict as needed.<\/p>\n<p><strong>Computerized tomography (CT)<\/strong><\/p>\n<p>A noninvasive imaging technique that uses computers to analyze several cross-sectional X-rays in order to reveal minute details about structures in the body.<\/p>\n<p><strong>Congenital<\/strong><\/p>\n<p>Present at birth.<\/p>\n<p><strong>Creatine kinase MB<\/strong><\/p>\n<p>An enzyme that catalyzes the conversion of creatine to phosphocreatine, consuming ATP.<\/p>\n<p><strong>Cyanosis <\/strong><\/p>\n<p>A condition in which the oxygen supply is restricted, causing the skin to look blue.<\/p>\n<p><strong>Diabetes mellitus<\/strong><\/p>\n<p>A disease in which the body does not control the amount of glucose (a type of sugar) in the blood and the kidneys make a large amount of urine. This disease occurs when the body does not make enough insulin or does not use it the way it should.<\/p>\n<p><strong>Diaphoresis<\/strong><\/p>\n<p>Sweating.<\/p>\n<p><strong>Diastole<\/strong><\/p>\n<p>Period of time when the heart muscle is relaxed and the chambers fill with blood.<\/p>\n<p><strong>Ductus arteriosus<\/strong><\/p>\n<p>A temporary connection between pulmonary trunk and aorta in the fetal heart.<\/p>\n<p><strong>Dyspnea<\/strong><\/p>\n<p>Difficulty breathing.<\/p>\n<p><strong>Echocardiogram<\/strong><\/p>\n<p>A computer picture of the heart created by bouncing high-energy sound waves (ultrasound) off internal tissues or organs of the chest.<\/p>\n<p><strong>Echocardiography<\/strong><\/p>\n<p>A procedure that uses high-energy sound waves (ultrasound) to look at tissues and organs inside the chest.<\/p>\n<p><strong>Electrocardiogram (ECG\/EKG)<\/strong><\/p>\n<p>The record of the heart&#8217;s function produced by the electrocardiograph.<\/p>\n<p><strong>Electrocardiograph<\/strong><\/p>\n<p>The instrument that generates an electrocardiogram (ECG); 10 electrodes are placed in standard locations on the patient&#8217;s skin to record heart function.<\/p>\n<p><strong>Electrocardiography<\/strong><\/p>\n<p>The science of recording the electrical activity of the heart.<\/p>\n<p><strong>Endocarditis<\/strong><\/p>\n<p>A condition in which the tissues lining the inside of the heart and the heart valves become inflamed.<\/p>\n<p><strong>Foramen ovale <\/strong><\/p>\n<p>An opening between right and left atria, which is normal in the fetal heart.<\/p>\n<p><strong>Great vessels <\/strong><\/p>\n<p>Include the superior vena cava, inferior vena cava, aorta and pulmonary trunk.<\/p>\n<p><strong>Heart murmur<\/strong><\/p>\n<p>An abnormal heart sound.<\/p>\n<p><strong>Heart rate<\/strong><\/p>\n<p>The number of times the heart beats within a certain time period, usually a minute.<\/p>\n<p><strong>High-density lipoprotein (HDL)<\/strong><\/p>\n<p>Often referred to as &#8220;good&#8221; cholesterol.<\/p>\n<p><strong>Hypercholesterolemia <\/strong><\/p>\n<p>Higher than normal levels of cholesterol in the blood.<\/p>\n<p><strong>Hyperlipidemia <\/strong><\/p>\n<p>Excessive fat in the blood.<\/p>\n<p><strong>Hypertension <\/strong><\/p>\n<p>Abnormally high blood pressure.<\/p>\n<p><strong>Implantable cardioverter defibrillators (ICD)<\/strong><\/p>\n<p>A small device placed by surgery in the chest or abdomen that is used to correct a heartbeat that is abnormal. Wires are passed through a vein to connect the device to the heart. When it detects abnormal heartbeats, it sends an electrical shock to the heart to restore the heartbeat to normal.<\/p>\n<p><strong>Inferior vena cava<\/strong><\/p>\n<p>One of the two largest veins in the body. It carries deoxygenated blood from the torso and legs back to the heart.<\/p>\n<p><strong>Interatrial septum<\/strong><\/p>\n<p>The wall separating the right and left atria.<\/p>\n<p><strong>Interventricular septum<\/strong><\/p>\n<p>The wall of myocardium that separates the right and left ventricles.<\/p>\n<p><strong>Ischemia<\/strong><\/p>\n<p>Lack of blood flow to body tissues.<\/p>\n<p><strong>Low-density lipoprotein (LDL)<\/strong><\/p>\n<p>Often referred to as &#8216;bad&#8217; cholesterol.<\/p>\n<p><strong>Magnetic Resonance Imaging (MRI)<\/strong><\/p>\n<p>A procedure in which radio waves and a powerful magnet linked to a computer are used to create detailed pictures of areas inside the body.<\/p>\n<p><strong>Mitral valve <\/strong><\/p>\n<p>Located at the opening between the left atrium and left ventricle; also known as the bicuspid valve.<\/p>\n<p><strong>Myocardial infarction (MI)<\/strong><\/p>\n<p>Heart attack, caused by lack of blood flow and oxygen to the heart.<\/p>\n<p><strong>Myocarditis<\/strong><\/p>\n<p>A rare condition in which the heart muscle becomes thick and inflamed and may also become weak.<\/p>\n<p><strong>Occlusion<\/strong><\/p>\n<p>A blockage.<\/p>\n<p><strong>Pacemaker<\/strong><\/p>\n<p>An electronic device that is implanted in the body to monitor heart rate and rhythm. It gives the heart electrical stimulation when it does not beat normally.<\/p>\n<p><strong>Palpitations<\/strong><\/p>\n<p>A rapid or irregular heartbeat that a person can feel.<\/p>\n<p><strong>Pericardial fluid<\/strong><\/p>\n<p>Watery fluid produced in the serous and visceral pericardium surrounding the surface of the heart.<\/p>\n<p><strong>Pericarditis<\/strong><\/p>\n<p>Inflammation of the (sac) surrounding the heart.<\/p>\n<p><strong>Pericardiocentesis<\/strong><\/p>\n<p>Surgical puncture to aspirate fluid from the (sac) surrounding the heart.<\/p>\n<p><strong>Plaque<\/strong><\/p>\n<p>A fatty material including cholesterol, connective tissue, white blood cells, and some smooth muscle cells.<\/p>\n<p><strong>Polycythemia<\/strong><\/p>\n<p>A rare disorder in which the bone marrow produces an abnormally large amount of blood cells.<\/p>\n<p><strong>Pulmonary trunk <\/strong><\/p>\n<p>The very large artery referred to as a trunk, a term indicating that the vessel gives rise to several smaller arteries.<\/p>\n<p><strong>Roots of the great vessels<\/strong><\/p>\n<p>The part of each great vessel (aorta, pulmonary trunk, inferior vena cava, superior vena cava) that connects to the base of the heart.<\/p>\n<p><strong>Serous membrane<\/strong><\/p>\n<p>One of the thin membranes that cover the walls and organs in the thoracic and abdominopelvic cavities.<\/p>\n<p><strong>Sinus rhythm<\/strong><\/p>\n<p>The normal electrical pattern followed by contraction of the heart.<\/p>\n<p><strong>Sphygmomanometer<\/strong><\/p>\n<p>A blood pressure cuff attached to a measuring device.<\/p>\n<p><strong>Stethoscope<\/strong><\/p>\n<p>An instrument used to hear sounds produced by the heart, lungs, or other parts of the body.<\/p>\n<p><strong>Superior vena cava<\/strong><\/p>\n<p>One of two large veins in the body, which carries deoxygenated blood from the head and upper extremities back to the heart.<\/p>\n<p><strong>Syncope<\/strong><\/p>\n<p>Fainting.<\/p>\n<p><strong>Systole<\/strong><\/p>\n<p>Period of time when the heart muscle is contracting.<\/p>\n<p><strong>Tachycardia<\/strong><\/p>\n<p>A condition in which the resting rate is above 100 bpm.<\/p>\n<p><strong>Valvuloplasty<\/strong><\/p>\n<p>The widening of a stenosed heart valve using a balloon catheter.<\/p>\n<h2>Test Yourself<\/h2>\n<div id=\"h5p-55\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-55\" class=\"h5p-iframe\" data-content-id=\"55\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Cardiovascular System: Test Yourself\"><\/iframe><\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<h2>References<\/h2>\n<p>Bureau of Labor Statistics. (2021). Medical sonographers and cardiovascular technologists and technicians. In <em>Occupational outlook handbook<\/em>. U.S. Department of Labor. <a href=\"https:\/\/www.bls.gov\/ooh\/healthcare\/diagnostic-medical-sonographers.htm\">https:\/\/www.bls.gov\/ooh\/healthcare\/diagnostic-medical-sonographers.htm <\/a><\/p>\n<p>Centers for Disease Control and Prevention. (n.d.-a). <em>Cardiomyopathy<\/em>. CDC. <a href=\"https:\/\/www.cdc.gov\/heartdisease\/cardiomyopathy.htm\">https:\/\/www.cdc.gov\/heartdisease\/cardiomyopathy.htm<\/a><\/p>\n<p>Centers for Disease Control and Prevention. (n.d.-b). <em>Valvular heart disease<\/em>. CDC. <a href=\"https:\/\/www.cdc.gov\/heartdisease\/valvular_disease.htm\">https:\/\/www.cdc.gov\/heartdisease\/valvular_disease.htm<\/a><\/p>\n<p>Centers for Disease Control and Prevention. (n.d.-c). <em>Aortic aneurysm<\/em>. CDC. <a href=\"https:\/\/www.cdc.gov\/heartdisease\/aortic_aneurysm.htm\">https:\/\/www.cdc.gov\/heartdisease\/aortic_aneurysm.htm<\/a><\/p>\n<p>CrashCourse. (2015, July 6). <em>The heart, part 1 &#8211; under pressure: Crash course A&amp;P #25 <\/em>[Video]. YouTube. <a href=\"https:\/\/youtu.be\/X9ZZ6tcxArI\">https:\/\/youtu.be\/X9ZZ6tcxArI<\/a><\/p>\n<p>CrashCourse. (2015, July 13). <em>The heart, part 2 &#8211; heart throbs: Crash course A&amp;P #26<\/em> [Video]. YouTube. <a href=\"https:\/\/youtu.be\/FLBMwcvOaEo\">https:\/\/youtu.be\/FLBMwcvOaEo<\/a><\/p>\n<p>National Heart, Lung, and Blood Institute. (n.d.). <em>Aortic aneurysm<\/em>. National Institutes of Health, U.S. Department of Health and Human Services. <a href=\"https:\/\/www.nhlbi.nih.gov\/health-topics\/aneurysm\">https:\/\/www.nhlbi.nih.gov\/health-topics\/aneurysm<\/a><\/p>\n<p>National Cancer Institute. (n.d.). <em>Definition of thoracic surgeon. <\/em>National Institutes of Health, U.S. Department of Health and Human Services.. <a href=\"https:\/\/www.cancer.gov\/publications\/dictionaries\/cancer-terms\/def\/thoracic-surgeon\">https:\/\/www.cancer.gov\/publications\/dictionaries\/cancer-terms\/def\/thoracic-surgeon<\/a><\/p>\n<p>New York State Education Department. (2020). <em>Perfusionist<\/em>. Retrieved November 1, 2021, from <a href=\"http:\/\/www.op.nysed.gov\/careers\/perfprofile.htm\">http:\/\/www.op.nysed.gov\/careers\/perfprofile.htm<\/a><\/p>\n<h2>Image Descriptions<\/h2>\n<p><a id=\"Figure9.1id\" href=\"\"><\/a><strong>Figure 9.1 image description:<\/strong> This diagram shows the location of the heart in the thorax (sagittal and anterior views). The sagittal view labels read (from top, clockwise): first rib, aortic arch, thoracic arch, esophagus, inferior vena cava, diaphragm, thymus, trachea. The anterior view labels read (from top, clockwise): mediastinum, arch of aorta, pulmonary trunk, left auricle, left lung, left ventricle, pericardial cavity, apex of heart, edge of parietal pericardium, diaphragm, edge of parietal pleura, ribs, right ventricle, right atrium, right auricle, right lung, superior vena cava. <a href=\"#Figure9.1\">[Return to Figure 9.1].<\/a><\/p>\n<p><a id=\"Figure9.2id\" href=\"\"><\/a><strong>Figure 9.2 image description:<\/strong> This image shows a magnified view of the structure of the heart wall. Labels read (from top, clockwise): pericardial cavity, fibrous pericardium, parietal layer of serous pericardium, epicardium (visceral layer of serous pericardium), myocardium, endocardium. <a href=\"#Figure9.2\">[Return to Figure 9.2].<\/a><\/p>\n<p><a id=\"Figure9.3id\" href=\"\"><\/a><strong>Figure 9.3 image description:<\/strong> This diagram shows the network of blood vessels in the lungs. Labels read (from top, clockwise (left-side of the body): aortic arch, pulmonary trunk, left lung, left pulmonary arteries, left pulmonary vein, pulmonary capillaries, descending aorta, (right side of body) inferior vena cava, right pulmonary veins, right pulmonary arteries, right lung, superior vena cava, ascending aorta. <a href=\"#Figure9.3\">[Return to Figure 9.3].<\/a><\/p>\n<p><a id=\"Figure9.4id\" href=\"\"><\/a><strong>Figure 9.4 image description:<\/strong> The top panel shows the human heart with the arteries and veins labeled (from top, clockwise): aorta, left pulmonary arteries, pulmonary trunk, left atrium, left pulmonary veins, aortic semilunar valve, mitral valve, left ventricle, inferior vena cava, right ventricle, tricuspid valve, right atrium, pulmonary semilunar valve, right pulmonary veins, right pulmonary arteries, superior vena cava. The bottom panel shows a rough map of the human circulatory system. Labels read (from top, clockwise): systemic capillaries of upper body, systemic arteries to upper body, pulmonary trunk, left atrium, left ventricle, systemic arteries to lower body, systemic capillaries of lower body, systemic veins from lower body, right ventricle, right atrium, pulmonary capillaries in lungs, systemic veins from upper body. <a href=\"#Figure9.4\">[Return to Figure 9.4].<\/a><\/p>\n<p><a id=\"Figure9.5id\" href=\"\"><\/a><strong>Figure 9.5 image description:<\/strong> The top panel of this figure shows the anterior view of the heart while the bottom panel shows the posterior view of the heart. The different blood vessels are labeled. Anterior view labels (from top of diagram, clockwise): left coronary artery, pulmonary trunk, circumflex artery, anterior interventricular artery, great cardiac vein, small cardiac vein, anterior cardiac veins, atrial arteries, right atrium, right coronary artery, ascending aorta, aortic arch. Posterior view labels (from top of diagram, clockwise): coronary sinus, small cardiac vein, right coronary artery, marginal artery, middle cardiac vein, posterior cardiac vein, posterior interventricular artery, marginal artery, great cardiac vein, circumflex artery. <a href=\"#Figure9.5\">[Return to Figure 9.5].<\/a><\/p>\n<p><a id=\"Figure9.6id\" href=\"\"><\/a><strong>Figure 9.6 image description:<\/strong> This image shows the anterior view of the frontal section of the heart with the major parts labeled. Labels read (from top of diagram, clockwise) arch of aorta, Bachman&#8217;s bundle, atrioventricular bundle (bundle of His), left ventricle, right and left bundle branches, Purkinje fibers, right ventricle, right atrium, posterior intermodal, middle intermodal, atrioventricular node, anterior intermodal, Sinoatrial node. <a href=\"#Figure9.6\">[Return to Figure 9.6].<\/a><\/p>\n<p><a id=\"Figure9.7id\" href=\"\"><\/a><strong>Figure 9.7 image description:<\/strong> This diagram shows the six different stages of heart contraction and relaxation along with the stages in the QT cycle. <a href=\"#Figure9.7\">[Return to Figure 9.7].<\/a><\/p>\n<p><a id=\"Figure9.8id\" href=\"\"><\/a><strong>Figure 9.8 image description:<\/strong> This diagram shows the arteries in the thoracic and abdominal cavity. Visceral branches of the thoracic aorta labels (from top): bronchial, esophageal, mediastinal, pericardial, thoracic aorta, aortic hiatus, celiac trunk, left gastric, splenic, common hepatic, superior mesenteric, abdominal aorta, inferior mesenteric, external iliac. Parietal (somatic) branches of thoracic aorta labels (from top): intercostal, superior phrenic, inferior phrenic, diaphragm, adrenal, renal, gonadal, lumbar, medial sacral, common iliac, internal iliac. <a href=\"#Figure9.8\">[Return to Figure 9.8].<\/a><\/p>\n<p><a id=\"Figure9.9id\" href=\"\"><\/a><strong>Figure 9.9 image description:<\/strong> This diagram shows the structure of the heart with different congenital defects. The top left panel shows patent foramen ovale (label reads foramen ovale fails to close), the top right panel shows coarctation of the aorta (label reads narrow segment of aorta), the bottom left panel shows patent ductus arteriosus (label reads Ductus arteriosus remains open) and the bottom right shows tetralogy of fallot (labels read aorta emerges from both ventricles, interventricular septal defect, enlarged right ventricle, stenosed pulmonary semilunar valve). <a href=\"#Figure9.9\">[Return to Figure 9.9].<\/a><\/p>\n<p><strong><a id=\"Figure9.10id\" href=\"\"><\/a>Figure <\/strong><strong>9.10 image description:<\/strong> An angiogram of atherosclerotic coronary arteries. The image shows blockages in the common trunk of the left coronary artery and circumflex artery. Blockages can cause ischemia, hypoxia, and myocardial infarction. <a href=\"\u201c#Figure9.10&quot;\">[Return to Figure 9.10].<\/a><\/p>\n<p><a id=\"Figure9.11id\" href=\"\"><\/a><strong>Figure 9.11 image description:<\/strong> In this image the QT cycle for different heart conditions are shown. From top to bottom, the arrhythmias shown are second-degree partial blocks (text reads: Note how half of the P waves are not followed by the QRS complex and T waves while the other half are. Question: what would you expect to happen to heart rate?), atrial fibrillation (text reads: Note the abnormal electric pattern prior to the QRS complexes. Also note how the frequency between the QRS complexes has increased. Question: What would you expect to happen to heart rate?), ventricular tachycardia (text reads: Note the unusual shape of the QRS complex, focusing on the S component. Question: What would you expect to happen to heart rate?), ventricular fibrillation (text reads: Note the total lack of normal electrical activity. Question: What would you expect to happen to heart rate?), and third degree block (text reads: Note that in a third-degree block some of the impulses initiated by the SA node do not reach the AV node while others do. Also note that the P waves are not followed by the QRS complex. Question: What would you expect to happen to heart rate?). <a href=\"#Figure9.11\">[Return to Figure 9.11].<\/a><\/p>\n<div class=\"textbox shaded\">Unless otherwise indicated, this chapter contains material adapted from <a href=\"https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/1-introduction\"><em>Anatomy and Physiology<\/em><\/a> (on <a href=\"https:\/\/openstax.org\/\">OpenStax<\/a>), by Betts et al. and is used under a <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY 4.0 international license<\/a>. Download and access this book for free at <a href=\"https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/1-introduction\">https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/1-introduction<\/a>.<\/div>\n<p>&nbsp;<\/p>\n<div class=\"glossary\"><span class=\"screen-reader-text\" id=\"definition\">definition<\/span><template id=\"term_93_369\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_369\"><div tabindex=\"-1\"><p>The number of times the heart beats within a certain time period, usually a minute (National Cancer Institute, n.d.)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_370\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_370\"><div tabindex=\"-1\"><p>Include the superior vena cava, inferior vena cava, aorta and pulmonary trunk (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_373\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_373\"><div tabindex=\"-1\"><p>The part of each great vessel (aorta, pulmonary trunk, inferior vena cava, superior vena cava) that connects to the base of the heart (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_372\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_372\"><div tabindex=\"-1\"><p>One of the thin membranes that cover the walls and organs in the thoracic and abdominopelvic cavities (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_375\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_375\"><div tabindex=\"-1\"><p>One of two large veins in the body, which carries deoxygenated blood from the head and upper extremities back to the heart (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_376\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_376\"><div tabindex=\"-1\"><p>One of the two largest veins in the body. It carries deoxygenated blood from the torso and legs back to the heart (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_421\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_421\"><div tabindex=\"-1\"><p>The very large artery referred to as a trunk, a term indicating that the vessel gives rise to several smaller arteries (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_410\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_410\"><div tabindex=\"-1\"><p>Mitral (bicuspid) valve that allows blood to flow from left atrium to left ventricle and tricuspid valve that allows blood to flow from right atrium to right ventricle (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_289\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_289\"><div tabindex=\"-1\"><p>The enlargement of muscles (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_250\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_250\"><div tabindex=\"-1\"><p>Abnormally high blood pressure (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_258\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_258\"><div tabindex=\"-1\"><p>Having no signs or symptoms of disease (National Cancer Institute, n.d.)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_295\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_295\"><div tabindex=\"-1\"><p>Difficulty breathing (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_411\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_411\"><div tabindex=\"-1\"><p>A deviation from the normal pattern of impulse conduction and contraction of the heart (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_385\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_385\"><div tabindex=\"-1\"><p>An abnormal heart sound (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_407\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_407\"><div tabindex=\"-1\"><p>Higher than normal levels of cholesterol in the blood (National Library of Medicine, 2021)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_403\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_403\"><div tabindex=\"-1\"><p>A hardening of the arteries that involves the accumulation of plaque (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_389\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_389\"><div tabindex=\"-1\"><p>A class of medications used to treat high blood pressure (National Cancer Institute, n.d.)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_627\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_627\"><div tabindex=\"-1\"><p>Pertaining to after birth (National Library of Medicine, 2021)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_387\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_387\"><div tabindex=\"-1\"><p>An opening between right and left atria, which is normal in the fetal heart (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_388\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_388\"><div tabindex=\"-1\"><p>A temporary connection between pulmonary trunk and aorta in the fetal heart (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_244\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_244\"><div tabindex=\"-1\"><p>Listening to the heart using a stethoscope (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_386\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_386\"><div tabindex=\"-1\"><p>The wall separating the right and left atria (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_401\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_401\"><div tabindex=\"-1\"><p>The wall of myocardium that separates the right and left ventricles (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_402\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_402\"><div tabindex=\"-1\"><p>A rare disorder in which the bone marrow produces an abnormally large amount of blood cells (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_246\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_246\"><div tabindex=\"-1\"><p>A condition in which the oxygen supply is restricted, causing the skin to look blue (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_247\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_247\"><div tabindex=\"-1\"><p>A procedure that uses high-energy sound waves (ultrasound) to look at tissues and organs inside the chest (National Cancer Institute, n.d.)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_404\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_404\"><div tabindex=\"-1\"><p>A fatty material including cholesterol, connective tissue, white blood cells, and some smooth muscle cells (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_400\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_400\"><div tabindex=\"-1\"><p>The ability of the blood vessels to dilate and constrict as needed (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_408\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_408\"><div tabindex=\"-1\"><p>Lack of blood flow to body tissues (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_406\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_406\"><div tabindex=\"-1\"><p>Chest pain. It may be a symptom of coronary artery disease and myocardial infarction (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_405\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_405\"><div tabindex=\"-1\"><p>An x-ray or computer image (CT scan or MRI) of the blood vessels and blood flow in the body. A dye may be injected through a catheter (small tube) into an artery or vein to make the blood vessels easier to see (National Cancer Institute, n.d.)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_249\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_249\"><div tabindex=\"-1\"><p>Excessive fat in the blood (National Library of Medicine, 2021)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_628\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_628\"><div tabindex=\"-1\"><p>A blockage (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_390\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_390\"><div tabindex=\"-1\"><p>A rapid or irregular heartbeat that a person can feel (National Cancer Institute, n.d.)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_391\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_391\"><div tabindex=\"-1\"><p>Sweating (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_392\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_392\"><div tabindex=\"-1\"><p>Fainting (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_481\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_481\"><div tabindex=\"-1\"><p>A type of bone marrow disease that causes an excessive production of immature erythrocytes (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_393\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_393\"><div tabindex=\"-1\"><p>A noninvasive imaging technique that uses computers to analyze several cross-sectional X-rays in order to reveal minute details about structures in the body (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_394\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_394\"><div tabindex=\"-1\"><p>A procedure in which radio waves and a powerful magnet linked to a computer are used to create detailed pictures of areas inside the body (National Cancer Institute, n.d.)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_395\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_395\"><div tabindex=\"-1\"><p>An enzyme that catalyzes the conversion of creatine to phosphocreatine, consuming ATP (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_396\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_396\"><div tabindex=\"-1\"><p>The regulatory protein for muscle contraction (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_397\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_397\"><div tabindex=\"-1\"><p>Often referred to as 'bad' cholesterol (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_398\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_398\"><div tabindex=\"-1\"><p>Often referred to as \"good\" cholesterol (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_399\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_399\"><div tabindex=\"-1\"><p>A disease in which the body does not control the amount of glucose (a type of sugar) in the blood and the kidneys make a large amount of urine. This disease occurs when the body does not make enough insulin or does not use it the way it should (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_276\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_276\"><div tabindex=\"-1\"><p>The instrument that generates an electrocardiogram (ECG); 10 electrodes are placed in standard locations on the patient's skin to record heart function (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_466\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_466\"><div tabindex=\"-1\"><p>The removal or destruction of a body part or tissue or its function. Ablation may be performed by surgery, hormones, drugs, radiofrequency, heat, or other methods (National Cancer Institute, n.d.)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_465\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_465\"><div tabindex=\"-1\"><p>A small device placed by surgery in the chest or abdomen that is used to correct a heartbeat that is abnormal. Wires are passed through a vein to connect the device to the heart. When it detects abnormal heartbeats, it sends an electrical shock to the heart to restore the heartbeat to normal (National Cancer Institute, n.d.)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_412\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_412\"><div tabindex=\"-1\"><p>The area of the heart where the atria and ventricles meet (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_413\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_413\"><div tabindex=\"-1\"><p>The normal electrical pattern followed by contraction of the heart (Betts et al., 2013)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_277\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_277\"><div tabindex=\"-1\"><p>The science of recording the electrical activity of the heart (National Library of Medicine, 2021)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_93_464\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_93_464\"><div tabindex=\"-1\"><p>An electronic device that is implanted in the body to monitor heart rate and rhythm. It gives the heart electrical stimulation when it does not beat normally (National Cancer Institute, n.d.)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><\/div>","protected":false},"author":32,"menu_order":9,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-93","chapter","type-chapter","status-publish","hentry"],"part":19,"_links":{"self":[{"href":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-json\/pressbooks\/v2\/chapters\/93","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-json\/wp\/v2\/users\/32"}],"version-history":[{"count":3,"href":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-json\/pressbooks\/v2\/chapters\/93\/revisions"}],"predecessor-version":[{"id":1502,"href":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-json\/pressbooks\/v2\/chapters\/93\/revisions\/1502"}],"part":[{"href":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-json\/pressbooks\/v2\/parts\/19"}],"metadata":[{"href":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-json\/pressbooks\/v2\/chapters\/93\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-json\/wp\/v2\/media?parent=93"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-json\/pressbooks\/v2\/chapter-type?post=93"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-json\/wp\/v2\/contributor?post=93"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/acchpr1040\/wp-json\/wp\/v2\/license?post=93"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}