Getting Rid of Wastes<\/h1>\r\n<\/div>\r\nThe many chimneys on these houses are one way that the inhabitants of the home get rid of the wastes they produce. The chimneys expel waste gases that are created when they burn fuel in their furnace or fireplace. Think about the other wastes that people create in their homes and how we dispose of them. Solid trash and recyclables may go to the curb in a trash can, or in a recycling bin for pick up and transport to a landfill or recycling centre. Wastewater from sinks, showers, toilets, and the washing machine goes into a main sewer pipe and out of the house to join the community\u2019s sanitary sewer system.\r\n\r\nLike a busy home, your body also produces a lot of wastes that must be eliminated. Like a home,\u00a0the way\u00a0your body gets rid of wastes depends on the nature of the waste products. Some\u00a0human body\u00a0wastes are gases, some are solids, and some are in a\u00a0liquid\u00a0state. Getting rid of body wastes is called excretion, and there are a number of different\u00a0organs of excretion in the human body.\r\n\r\nExcretion<\/h3>\r\n<\/div>\r\n[pb_glossary id=\"4705\"]Excretion[\/pb_glossary]<\/strong>\u00a0is the process of removing wastes and excess\u00a0water\u00a0from the body. It is an essential process in all living things, and it is one of the major ways the\u00a0human body\u00a0maintains\u00a0[pb_glossary id=\"5761\"]homeostasis[\/pb_glossary]. It also helps prevent damage to the body. Wastes include by-products of [pb_glossary id=\"5773\"]metabolism[\/pb_glossary] \u2014 some of which are toxic \u2014 and other non-useful materials, such as used up and broken down components. Some of the specific waste products that must be excreted from the body include carbon dioxide from\u00a0[pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary], [pb_glossary id=\"4707\"]ammonia[\/pb_glossary] and\u00a0[pb_glossary id=\"4708\"]urea[\/pb_glossary]<\/strong>\u00a0from\u00a0protein\u00a0catabolism, and\u00a0[pb_glossary id=\"4709\"]uric\u00a0acid<\/strong>[\/pb_glossary]\u00a0from\u00a0nucleic acid\u00a0catabolism.\r\n\r\nExcretory Organs<\/h3>\r\n<\/div>\r\nOrgans of excretion include the [pb_glossary id=\"3521\"]skin[\/pb_glossary], [pb_glossary id=\"2989\"]liver[\/pb_glossary], [pb_glossary id=\"4560\"]large intestine[\/pb_glossary], [pb_glossary id=\"2990\"]lungs[\/pb_glossary], and [pb_glossary id=\"2988\"]kidneys[\/pb_glossary] (see Figure 16.2.2). Together, these organs make up the [pb_glossary id=\"5999\"]excretory system[\/pb_glossary]<\/strong>.\u00a0They all\u00a0excrete wastes, but they don\u2019t work together in the same way that organs do in most other body systems. Each of the excretory organs \u201cdoes its own thing\u201d more-or-less independently of the others, but all are necessary to successfully excrete the full range of wastes from the\u00a0human body.\r\n\r\n[h5p id=\"628\"]\r\n\r\n\r\nFigure 16.2.2 Internal organs of excretion are identified in this illustration. They include the skin, liver, large intestine, lungs, and kidneys.<\/em>\r\n\r\n<\/div>\r\nSkin<\/h2>\r\n[caption id=\"attachment_4712\" align=\"alignright\" width=\"421\"]![\"16.2.3](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/gym_room_fitness_equipment_cardiovascular_exercise_elliptical_bike_cardio_training_sports_equipment_bodybuilding-825364-2.jpg\")
Figure 16.2.3 The purpose of sweat production is mainly to cool the body and prevent overheating, but it also contributes to excretion.<\/em>[\/caption]\r\n\r\nThe [pb_glossary id=\"3521\"]skin[\/pb_glossary] is part of the integumentary system, but it also plays a role in excretion through the production of [pb_glossary id=\"4711\"]sweat[\/pb_glossary] by sweat glands in the dermis. Although the main role of sweat production is to cool the body and maintain temperature [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary], sweating also eliminates excess water and salts, as well as a small amount of urea. When sweating is copious, as in Figure 16.2.3, ingestion of salts and water may be helpful to maintain homeostasis in the body.\r\nLiver<\/h2>\r\n[caption id=\"attachment_4713\" align=\"alignleft\" width=\"333\"]![\"16.2.4](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/liver-2934612_1280-2.png\")
Figure 16.2.4 The liver is an organ of excretion.<\/em>[\/caption]\r\n\r\nThe liver (shown in Figure 16.2.4) has numerous major functions, including secreting [pb_glossary id=\"4599\"]bile[\/pb_glossary] for digestion of lipids, synthesizing many proteins and other compounds, storing [pb_glossary id=\"327\"]glycogen[\/pb_glossary] and other substances, and secreting endocrine hormones. In addition to all of these functions, the liver is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. For example, the liver transforms [pb_glossary id=\"4707\"]ammonia[\/pb_glossary] \u2014 a poisonous by-product of protein [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] \u2014 into [pb_glossary id=\"4708\"]urea[\/pb_glossary], which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary],<\/strong>\u00a0a byproduct of [pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary] [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] that forms when red\u00a0blood\u00a0cells\u00a0die. Bile travels to the\u00a0small intestine\u00a0and is then excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the\u00a0[pb_glossary id=\"4560\"]large intestine[\/pb_glossary].\r\nLarge Intestine<\/h2>\r\nThe [pb_glossary id=\"4560\"]large intestine[\/pb_glossary] is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. The large intestine also collects wastes from throughout the body. [pb_glossary id=\"4599\"]Bile[\/pb_glossary] secreted into the gastrointestinal tract, for example, contains the waste product [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] from the liver. Bilirubin is a brown pigment that gives human [pb_glossary id=\"4636\"]feces[\/pb_glossary] its characteristic brown colour.\r\nLungs<\/h2>\r\nThe lungs are part of the respiratory system (shown in Figure 16.2.5), but they are also important organs of excretion. They are responsible for the excretion of gaseous wastes from the body. The main waste gas excreted by the lungs is carbon dioxide, which is a waste product of [pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary] in cells throughout the body. Carbon dioxide is diffused from the blood into the air in the tiny air sacs called [pb_glossary id=\"4311\"]alveoli[\/pb_glossary] in the lungs (shown in the inset diagram). By expelling carbon dioxide from the blood, the lungs help maintain acid-base [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary]. In fact, it is the pH of blood that controls the rate of breathing. Water vapor is also picked up from the lungs and other organs of the respiratory tract as the exhaled air passes over their moist linings, and the water vapor is excreted along with the carbon dioxide. Trace levels of some other waste gases are exhaled, as well.\r\n\r\n[caption id=\"attachment_8003\" align=\"aligncenter\" width=\"699\"]![\"16.2.5](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/1024px-Respiratory_System_Illustration-2.png\")
Figure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.[\/caption]\r\nKidneys<\/h2>\r\nThe paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0[pb_glossary id=\"4717\"]urine[\/pb_glossary]<\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0[pb_glossary id=\"4718\"]Nephrons[\/pb_glossary]<\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.\r\n\r\n[caption id=\"attachment_4719\" align=\"aligncenter\" width=\"512\"]![\"16.2.6](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/512px-Urinary_System_Female-2.png\")
Figure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em>[\/caption]\r\n\r\nBy producing and excreting urine, the kidneys play vital roles in body-wide [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary]. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.\r\n\r\n\r\n16.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- [pb_glossary id=\"4705\"]Excretion[\/pb_glossary] is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary].<\/li>\r\n \t
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the [pb_glossary id=\"5999\"]excretory system[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"3521\"]skin[\/pb_glossary] plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of [pb_glossary id=\"4708\"]urea[\/pb_glossary], a byproduct of\u00a0protein\u00a0catabolism.<\/li>\r\n \t
- The [pb_glossary id=\"2989\"]liver[\/pb_glossary] is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] \u2014 a waste product of [pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary] [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] \u2014 in bile. Bile then travels to the\u00a0[pb_glossary id=\"4559\"]small intestine[\/pb_glossary], and is eventually excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the [pb_glossary id=\"4560\"]large intestine[\/pb_glossary].<\/li>\r\n \t
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in [pb_glossary id=\"4599\"]bile[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"2990\"]lungs[\/pb_glossary] are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0[pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary]\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\r\n \t
- The paired [pb_glossary id=\"2988\"]kidneys[\/pb_glossary] are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called [pb_glossary id=\"4718\"]nephrons[\/pb_glossary]\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as [pb_glossary id=\"4717\"]urine[\/pb_glossary]. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is excretion, and what is its significance?<\/li>\r\n \t
- [h5p id=\"629\"]<\/li>\r\n \t
- Describe the excretory functions of the liver.<\/li>\r\n \t
- What are\u00a0the main excretory functions of the large intestine?<\/li>\r\n \t
- List organs of the urinary system.<\/li>\r\n \t
- Describe the physical states in which the wastes from the human body are excreted.<\/li>\r\n \t
- Give one example of why ridding the body of excess water is important.<\/li>\r\n \t
- What gives feces its brown colour? Why is that substance produced?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be\r\nWhy Can We Regrow A Liver (But Not A Limb)? MITK12Videos, 2015.<\/p>\r\n
https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
Are Sports Drinks Good For You? | Fit or Fiction, POPSUGAR Fitness, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be\r\n
Why do we sweat? - John Murnan, TED-Ed, 2018.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n
Attributions<\/h2>\r\nFigure 16.2.1<\/strong>\r\n\r\nChimneys\/ Kingston upon Hull, England<\/span><\/a> [photo] by Angela Baker<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\r\n\r\nFigure 16.2.2<\/strong>\r\n\r\n \t- Sweat or rain?<\/a> by Kullez<\/a> on Flickr<\/a> is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0\/).<\/li>\r\n \t
- Kidney front - white<\/a> from www.medicalgraphics.de<\/a> is used under a CC BY-ND 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nd\/4.0\/) license.<\/li>\r\n \t
- File:Liver Cirrhosis.png<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- File:Human lungs.png<\/a> by Sharanyaudupa<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- Tags: Offal Marking Medical Intestine Liver<\/a> by Elionas2<\/a> on Pixabay<\/a> is used under the Pixabay license<\/a> (https:\/\/pixabay.com\/service\/license\/).<\/li>\r\n<\/ul>\r\n<\/div>\r\nFigure 16.2.3<\/strong>\r\n\r\n\r\ngym_room_fitness_equipment_cardiovascular_exercise_elliptical_bike_cardio_training_sports_equipment_bodybuilding-825364<\/a> from Pxhere<\/a> is used under a CC0 1.0<\/a> Universal public domain dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/).\r\n\r\nFigure 16.2.4<\/strong>\r\n\r\nTags: Liver Organ Anatomy<\/a> by zachvanstone8<\/a> on Pixabay<\/a> is used under the Pixabay License<\/a> (https:\/\/pixabay.com\/service\/license\/).\r\n\r\nFigure 16.2.5<\/strong>\r\n\r\nLung_and_diaphragm<\/a> by Terese Winslow\/ National Cancer Institute<\/a> on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 16.2.6<\/strong>\r\n\r\n512px-Urinary_System_(Female)<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\n\r\nReferences<\/span>\r\n
MITK12Videos. (2015, June 4). Why can we regrow a liver (but not a limb)? https:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be<\/p>\r\n
POPSUGAR Fitness. (2014, February 7). Are sports drinks good for you? | Fit or Fiction. YouTube. https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
TED-Ed. (2018, May 15). Why do we sweat? - John Murnan. YouTube. https:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be<\/p>\r\n\r\n<\/div>","rendered":"
<\/p>\n![\"16.2.1](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2019\/06\/Chimneys-by-angela-baker-awlR2geeTGs-unsplash-scaled-3.jpg\")
Figure 16.2.1 Chimney view.<\/em><\/figcaption><\/figure>\n\nGetting Rid of Wastes<\/h1>\n<\/div>\n
The many chimneys on these houses are one way that the inhabitants of the home get rid of the wastes they produce. The chimneys expel waste gases that are created when they burn fuel in their furnace or fireplace. Think about the other wastes that people create in their homes and how we dispose of them. Solid trash and recyclables may go to the curb in a trash can, or in a recycling bin for pick up and transport to a landfill or recycling centre. Wastewater from sinks, showers, toilets, and the washing machine goes into a main sewer pipe and out of the house to join the community\u2019s sanitary sewer system.<\/p>\n
Like a busy home, your body also produces a lot of wastes that must be eliminated. Like a home,\u00a0the way\u00a0your body gets rid of wastes depends on the nature of the waste products. Some\u00a0human body\u00a0wastes are gases, some are solids, and some are in a\u00a0liquid\u00a0state. Getting rid of body wastes is called excretion, and there are a number of different\u00a0organs of excretion in the human body.<\/p>\n
\nExcretion<\/h3>\n<\/div>\n
Excretion<\/a><\/strong>\u00a0is the process of removing wastes and excess\u00a0water\u00a0from the body. It is an essential process in all living things, and it is one of the major ways the\u00a0human body\u00a0maintains\u00a0homeostasis<\/a>. It also helps prevent damage to the body. Wastes include by-products of metabolism<\/a> \u2014 some of which are toxic \u2014 and other non-useful materials, such as used up and broken down components. Some of the specific waste products that must be excreted from the body include carbon dioxide from\u00a0cellular respiration<\/a>, ammonia<\/a> and\u00a0urea<\/a><\/strong>\u00a0from\u00a0protein\u00a0catabolism, and\u00a0uric\u00a0acid<\/strong><\/a>\u00a0from\u00a0nucleic acid\u00a0catabolism.<\/p>\n\nExcretory Organs<\/h3>\n<\/div>\n
Organs of excretion include the skin<\/a>, liver<\/a>, large intestine<\/a>, lungs<\/a>, and kidneys<\/a> (see Figure 16.2.2). Together, these organs make up the excretory system<\/a><\/strong>.\u00a0They all\u00a0excrete wastes, but they don\u2019t work together in the same way that organs do in most other body systems. Each of the excretory organs \u201cdoes its own thing\u201d more-or-less independently of the others, but all are necessary to successfully excrete the full range of wastes from the\u00a0human body.<\/p>\n\n<\/div>\n<\/div>\n\nFigure 16.2.2 Internal organs of excretion are identified in this illustration. They include the skin, liver, large intestine, lungs, and kidneys.<\/em><\/p>\n<\/div>\nSkin<\/h2>\nFigure 16.2.3 The purpose of sweat production is mainly to cool the body and prevent overheating, but it also contributes to excretion.<\/em><\/figcaption><\/figure>\nThe skin<\/a> is part of the integumentary system, but it also plays a role in excretion through the production of sweat<\/a> by sweat glands in the dermis. Although the main role of sweat production is to cool the body and maintain temperature homeostasis<\/a>, sweating also eliminates excess water and salts, as well as a small amount of urea. When sweating is copious, as in Figure 16.2.3, ingestion of salts and water may be helpful to maintain homeostasis in the body.<\/p>\nLiver<\/h2>\nFigure 16.2.4 The liver is an organ of excretion.<\/em><\/figcaption><\/figure>\nThe liver (shown in Figure 16.2.4) has numerous major functions, including secreting bile<\/a> for digestion of lipids, synthesizing many proteins and other compounds, storing glycogen and other substances, and secreting endocrine hormones. In addition to all of these functions, the liver is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. For example, the liver transforms ammonia<\/a> \u2014 a poisonous by-product of protein catabolism<\/a> \u2014 into urea<\/a>, which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein bilirubin<\/a>,<\/strong>\u00a0a byproduct of hemoglobin<\/a> catabolism<\/a> that forms when red\u00a0blood\u00a0cells\u00a0die. Bile travels to the\u00a0small intestine\u00a0and is then excreted in feces<\/a> by the\u00a0large intestine<\/a>.<\/p>\nLarge Intestine<\/h2>\n
The large intestine<\/a> is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. The large intestine also collects wastes from throughout the body. Bile<\/a> secreted into the gastrointestinal tract, for example, contains the waste product bilirubin<\/a> from the liver. Bilirubin is a brown pigment that gives human feces<\/a> its characteristic brown colour.<\/p>\nLungs<\/h2>\n
The lungs are part of the respiratory system (shown in Figure 16.2.5), but they are also important organs of excretion. They are responsible for the excretion of gaseous wastes from the body. The main waste gas excreted by the lungs is carbon dioxide, which is a waste product of cellular respiration<\/a> in cells throughout the body. Carbon dioxide is diffused from the blood into the air in the tiny air sacs called alveoli<\/a> in the lungs (shown in the inset diagram). By expelling carbon dioxide from the blood, the lungs help maintain acid-base homeostasis<\/a>. In fact, it is the pH of blood that controls the rate of breathing. Water vapor is also picked up from the lungs and other organs of the respiratory tract as the exhaled air passes over their moist linings, and the water vapor is excreted along with the carbon dioxide. Trace levels of some other waste gases are exhaled, as well.<\/p>\nFigure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.<\/figcaption><\/figure>\nKidneys<\/h2>\n
The paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0urine<\/a><\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0Nephrons<\/a><\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.<\/p>\nFigure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em><\/figcaption><\/figure>\nBy producing and excreting urine, the kidneys play vital roles in body-wide homeostasis<\/a>. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.<\/p>\n\n\n\n16.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- Excretion<\/a> is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains homeostasis<\/a>.<\/li>\n
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the excretory system<\/a>.<\/li>\n
- The skin<\/a> plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of urea<\/a>, a byproduct of\u00a0protein\u00a0catabolism.<\/li>\n
- The liver<\/a> is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes bilirubin<\/a> \u2014 a waste product of hemoglobin<\/a> catabolism<\/a> \u2014 in bile. Bile then travels to the\u00a0small intestine<\/a>, and is eventually excreted in feces<\/a> by the large intestine<\/a>.<\/li>\n
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in bile<\/a>.<\/li>\n
- The lungs<\/a> are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0cellular respiration<\/a>\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\n
- The paired kidneys<\/a> are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called nephrons<\/a>\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine<\/a>. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n16.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- What is excretion, and what is its significance?<\/li>\n
- \n\n
Excretion<\/h3>\r\n<\/div>\r\n[pb_glossary id=\"4705\"]Excretion[\/pb_glossary]<\/strong>\u00a0is the process of removing wastes and excess\u00a0water\u00a0from the body. It is an essential process in all living things, and it is one of the major ways the\u00a0human body\u00a0maintains\u00a0[pb_glossary id=\"5761\"]homeostasis[\/pb_glossary]. It also helps prevent damage to the body. Wastes include by-products of [pb_glossary id=\"5773\"]metabolism[\/pb_glossary] \u2014 some of which are toxic \u2014 and other non-useful materials, such as used up and broken down components. Some of the specific waste products that must be excreted from the body include carbon dioxide from\u00a0[pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary], [pb_glossary id=\"4707\"]ammonia[\/pb_glossary] and\u00a0[pb_glossary id=\"4708\"]urea[\/pb_glossary]<\/strong>\u00a0from\u00a0protein\u00a0catabolism, and\u00a0[pb_glossary id=\"4709\"]uric\u00a0acid<\/strong>[\/pb_glossary]\u00a0from\u00a0nucleic acid\u00a0catabolism.\r\n\r\nExcretory Organs<\/h3>\r\n<\/div>\r\nOrgans of excretion include the [pb_glossary id=\"3521\"]skin[\/pb_glossary], [pb_glossary id=\"2989\"]liver[\/pb_glossary], [pb_glossary id=\"4560\"]large intestine[\/pb_glossary], [pb_glossary id=\"2990\"]lungs[\/pb_glossary], and [pb_glossary id=\"2988\"]kidneys[\/pb_glossary] (see Figure 16.2.2). Together, these organs make up the [pb_glossary id=\"5999\"]excretory system[\/pb_glossary]<\/strong>.\u00a0They all\u00a0excrete wastes, but they don\u2019t work together in the same way that organs do in most other body systems. Each of the excretory organs \u201cdoes its own thing\u201d more-or-less independently of the others, but all are necessary to successfully excrete the full range of wastes from the\u00a0human body.\r\n\r\n[h5p id=\"628\"]\r\n\r\n\r\nFigure 16.2.2 Internal organs of excretion are identified in this illustration. They include the skin, liver, large intestine, lungs, and kidneys.<\/em>\r\n\r\n<\/div>\r\nSkin<\/h2>\r\n[caption id=\"attachment_4712\" align=\"alignright\" width=\"421\"] Figure 16.2.3 The purpose of sweat production is mainly to cool the body and prevent overheating, but it also contributes to excretion.<\/em>[\/caption]\r\n\r\nThe [pb_glossary id=\"3521\"]skin[\/pb_glossary] is part of the integumentary system, but it also plays a role in excretion through the production of [pb_glossary id=\"4711\"]sweat[\/pb_glossary] by sweat glands in the dermis. Although the main role of sweat production is to cool the body and maintain temperature [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary], sweating also eliminates excess water and salts, as well as a small amount of urea. When sweating is copious, as in Figure 16.2.3, ingestion of salts and water may be helpful to maintain homeostasis in the body.\r\nLiver<\/h2>\r\n[caption id=\"attachment_4713\" align=\"alignleft\" width=\"333\"] Figure 16.2.4 The liver is an organ of excretion.<\/em>[\/caption]\r\n\r\nThe liver (shown in Figure 16.2.4) has numerous major functions, including secreting [pb_glossary id=\"4599\"]bile[\/pb_glossary] for digestion of lipids, synthesizing many proteins and other compounds, storing [pb_glossary id=\"327\"]glycogen[\/pb_glossary] and other substances, and secreting endocrine hormones. In addition to all of these functions, the liver is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. For example, the liver transforms [pb_glossary id=\"4707\"]ammonia[\/pb_glossary] \u2014 a poisonous by-product of protein [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] \u2014 into [pb_glossary id=\"4708\"]urea[\/pb_glossary], which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary],<\/strong>\u00a0a byproduct of [pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary] [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] that forms when red\u00a0blood\u00a0cells\u00a0die. Bile travels to the\u00a0small intestine\u00a0and is then excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the\u00a0[pb_glossary id=\"4560\"]large intestine[\/pb_glossary].\r\nLarge Intestine<\/h2>\r\nThe [pb_glossary id=\"4560\"]large intestine[\/pb_glossary] is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. The large intestine also collects wastes from throughout the body. [pb_glossary id=\"4599\"]Bile[\/pb_glossary] secreted into the gastrointestinal tract, for example, contains the waste product [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] from the liver. Bilirubin is a brown pigment that gives human [pb_glossary id=\"4636\"]feces[\/pb_glossary] its characteristic brown colour.\r\nLungs<\/h2>\r\nThe lungs are part of the respiratory system (shown in Figure 16.2.5), but they are also important organs of excretion. They are responsible for the excretion of gaseous wastes from the body. The main waste gas excreted by the lungs is carbon dioxide, which is a waste product of [pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary] in cells throughout the body. Carbon dioxide is diffused from the blood into the air in the tiny air sacs called [pb_glossary id=\"4311\"]alveoli[\/pb_glossary] in the lungs (shown in the inset diagram). By expelling carbon dioxide from the blood, the lungs help maintain acid-base [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary]. In fact, it is the pH of blood that controls the rate of breathing. Water vapor is also picked up from the lungs and other organs of the respiratory tract as the exhaled air passes over their moist linings, and the water vapor is excreted along with the carbon dioxide. Trace levels of some other waste gases are exhaled, as well.\r\n\r\n[caption id=\"attachment_8003\" align=\"aligncenter\" width=\"699\"] Figure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.[\/caption]\r\nKidneys<\/h2>\r\nThe paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0[pb_glossary id=\"4717\"]urine[\/pb_glossary]<\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0[pb_glossary id=\"4718\"]Nephrons[\/pb_glossary]<\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.\r\n\r\n[caption id=\"attachment_4719\" align=\"aligncenter\" width=\"512\"] Figure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em>[\/caption]\r\n\r\nBy producing and excreting urine, the kidneys play vital roles in body-wide [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary]. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.\r\n\r\n\r\n16.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- [pb_glossary id=\"4705\"]Excretion[\/pb_glossary] is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary].<\/li>\r\n \t
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the [pb_glossary id=\"5999\"]excretory system[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"3521\"]skin[\/pb_glossary] plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of [pb_glossary id=\"4708\"]urea[\/pb_glossary], a byproduct of\u00a0protein\u00a0catabolism.<\/li>\r\n \t
- The [pb_glossary id=\"2989\"]liver[\/pb_glossary] is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] \u2014 a waste product of [pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary] [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] \u2014 in bile. Bile then travels to the\u00a0[pb_glossary id=\"4559\"]small intestine[\/pb_glossary], and is eventually excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the [pb_glossary id=\"4560\"]large intestine[\/pb_glossary].<\/li>\r\n \t
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in [pb_glossary id=\"4599\"]bile[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"2990\"]lungs[\/pb_glossary] are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0[pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary]\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\r\n \t
- The paired [pb_glossary id=\"2988\"]kidneys[\/pb_glossary] are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called [pb_glossary id=\"4718\"]nephrons[\/pb_glossary]\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as [pb_glossary id=\"4717\"]urine[\/pb_glossary]. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is excretion, and what is its significance?<\/li>\r\n \t
- [h5p id=\"629\"]<\/li>\r\n \t
- Describe the excretory functions of the liver.<\/li>\r\n \t
- What are\u00a0the main excretory functions of the large intestine?<\/li>\r\n \t
- List organs of the urinary system.<\/li>\r\n \t
- Describe the physical states in which the wastes from the human body are excreted.<\/li>\r\n \t
- Give one example of why ridding the body of excess water is important.<\/li>\r\n \t
- What gives feces its brown colour? Why is that substance produced?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be\r\nWhy Can We Regrow A Liver (But Not A Limb)? MITK12Videos, 2015.<\/p>\r\n
https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
Are Sports Drinks Good For You? | Fit or Fiction, POPSUGAR Fitness, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be\r\n
Why do we sweat? - John Murnan, TED-Ed, 2018.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n
Attributions<\/h2>\r\nFigure 16.2.1<\/strong>\r\n\r\nChimneys\/ Kingston upon Hull, England<\/span><\/a> [photo] by Angela Baker<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\r\n\r\nFigure 16.2.2<\/strong>\r\n\r\n \t- Sweat or rain?<\/a> by Kullez<\/a> on Flickr<\/a> is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0\/).<\/li>\r\n \t
- Kidney front - white<\/a> from www.medicalgraphics.de<\/a> is used under a CC BY-ND 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nd\/4.0\/) license.<\/li>\r\n \t
- File:Liver Cirrhosis.png<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- File:Human lungs.png<\/a> by Sharanyaudupa<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- Tags: Offal Marking Medical Intestine Liver<\/a> by Elionas2<\/a> on Pixabay<\/a> is used under the Pixabay license<\/a> (https:\/\/pixabay.com\/service\/license\/).<\/li>\r\n<\/ul>\r\n<\/div>\r\nFigure 16.2.3<\/strong>\r\n\r\n\r\ngym_room_fitness_equipment_cardiovascular_exercise_elliptical_bike_cardio_training_sports_equipment_bodybuilding-825364<\/a> from Pxhere<\/a> is used under a CC0 1.0<\/a> Universal public domain dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/).\r\n\r\nFigure 16.2.4<\/strong>\r\n\r\nTags: Liver Organ Anatomy<\/a> by zachvanstone8<\/a> on Pixabay<\/a> is used under the Pixabay License<\/a> (https:\/\/pixabay.com\/service\/license\/).\r\n\r\nFigure 16.2.5<\/strong>\r\n\r\nLung_and_diaphragm<\/a> by Terese Winslow\/ National Cancer Institute<\/a> on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 16.2.6<\/strong>\r\n\r\n512px-Urinary_System_(Female)<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\n\r\nReferences<\/span>\r\n
MITK12Videos. (2015, June 4). Why can we regrow a liver (but not a limb)? https:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be<\/p>\r\n
POPSUGAR Fitness. (2014, February 7). Are sports drinks good for you? | Fit or Fiction. YouTube. https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
TED-Ed. (2018, May 15). Why do we sweat? - John Murnan. YouTube. https:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be<\/p>\r\n\r\n<\/div>","rendered":"
<\/p>\nFigure 16.2.1 Chimney view.<\/em><\/figcaption><\/figure>\n\nGetting Rid of Wastes<\/h1>\n<\/div>\n
The many chimneys on these houses are one way that the inhabitants of the home get rid of the wastes they produce. The chimneys expel waste gases that are created when they burn fuel in their furnace or fireplace. Think about the other wastes that people create in their homes and how we dispose of them. Solid trash and recyclables may go to the curb in a trash can, or in a recycling bin for pick up and transport to a landfill or recycling centre. Wastewater from sinks, showers, toilets, and the washing machine goes into a main sewer pipe and out of the house to join the community\u2019s sanitary sewer system.<\/p>\n
Like a busy home, your body also produces a lot of wastes that must be eliminated. Like a home,\u00a0the way\u00a0your body gets rid of wastes depends on the nature of the waste products. Some\u00a0human body\u00a0wastes are gases, some are solids, and some are in a\u00a0liquid\u00a0state. Getting rid of body wastes is called excretion, and there are a number of different\u00a0organs of excretion in the human body.<\/p>\n
\nExcretion<\/h3>\n<\/div>\n
Excretion<\/a><\/strong>\u00a0is the process of removing wastes and excess\u00a0water\u00a0from the body. It is an essential process in all living things, and it is one of the major ways the\u00a0human body\u00a0maintains\u00a0homeostasis<\/a>. It also helps prevent damage to the body. Wastes include by-products of metabolism<\/a> \u2014 some of which are toxic \u2014 and other non-useful materials, such as used up and broken down components. Some of the specific waste products that must be excreted from the body include carbon dioxide from\u00a0cellular respiration<\/a>, ammonia<\/a> and\u00a0urea<\/a><\/strong>\u00a0from\u00a0protein\u00a0catabolism, and\u00a0uric\u00a0acid<\/strong><\/a>\u00a0from\u00a0nucleic acid\u00a0catabolism.<\/p>\n\nExcretory Organs<\/h3>\n<\/div>\n
Organs of excretion include the skin<\/a>, liver<\/a>, large intestine<\/a>, lungs<\/a>, and kidneys<\/a> (see Figure 16.2.2). Together, these organs make up the excretory system<\/a><\/strong>.\u00a0They all\u00a0excrete wastes, but they don\u2019t work together in the same way that organs do in most other body systems. Each of the excretory organs \u201cdoes its own thing\u201d more-or-less independently of the others, but all are necessary to successfully excrete the full range of wastes from the\u00a0human body.<\/p>\n\n<\/div>\n<\/div>\n\nFigure 16.2.2 Internal organs of excretion are identified in this illustration. They include the skin, liver, large intestine, lungs, and kidneys.<\/em><\/p>\n<\/div>\nSkin<\/h2>\nFigure 16.2.3 The purpose of sweat production is mainly to cool the body and prevent overheating, but it also contributes to excretion.<\/em><\/figcaption><\/figure>\nThe skin<\/a> is part of the integumentary system, but it also plays a role in excretion through the production of sweat<\/a> by sweat glands in the dermis. Although the main role of sweat production is to cool the body and maintain temperature homeostasis<\/a>, sweating also eliminates excess water and salts, as well as a small amount of urea. When sweating is copious, as in Figure 16.2.3, ingestion of salts and water may be helpful to maintain homeostasis in the body.<\/p>\nLiver<\/h2>\nFigure 16.2.4 The liver is an organ of excretion.<\/em><\/figcaption><\/figure>\nThe liver (shown in Figure 16.2.4) has numerous major functions, including secreting bile<\/a> for digestion of lipids, synthesizing many proteins and other compounds, storing glycogen and other substances, and secreting endocrine hormones. In addition to all of these functions, the liver is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. For example, the liver transforms ammonia<\/a> \u2014 a poisonous by-product of protein catabolism<\/a> \u2014 into urea<\/a>, which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein bilirubin<\/a>,<\/strong>\u00a0a byproduct of hemoglobin<\/a> catabolism<\/a> that forms when red\u00a0blood\u00a0cells\u00a0die. Bile travels to the\u00a0small intestine\u00a0and is then excreted in feces<\/a> by the\u00a0large intestine<\/a>.<\/p>\nLarge Intestine<\/h2>\n
The large intestine<\/a> is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. The large intestine also collects wastes from throughout the body. Bile<\/a> secreted into the gastrointestinal tract, for example, contains the waste product bilirubin<\/a> from the liver. Bilirubin is a brown pigment that gives human feces<\/a> its characteristic brown colour.<\/p>\nLungs<\/h2>\n
The lungs are part of the respiratory system (shown in Figure 16.2.5), but they are also important organs of excretion. They are responsible for the excretion of gaseous wastes from the body. The main waste gas excreted by the lungs is carbon dioxide, which is a waste product of cellular respiration<\/a> in cells throughout the body. Carbon dioxide is diffused from the blood into the air in the tiny air sacs called alveoli<\/a> in the lungs (shown in the inset diagram). By expelling carbon dioxide from the blood, the lungs help maintain acid-base homeostasis<\/a>. In fact, it is the pH of blood that controls the rate of breathing. Water vapor is also picked up from the lungs and other organs of the respiratory tract as the exhaled air passes over their moist linings, and the water vapor is excreted along with the carbon dioxide. Trace levels of some other waste gases are exhaled, as well.<\/p>\nFigure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.<\/figcaption><\/figure>\nKidneys<\/h2>\n
The paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0urine<\/a><\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0Nephrons<\/a><\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.<\/p>\nFigure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em><\/figcaption><\/figure>\nBy producing and excreting urine, the kidneys play vital roles in body-wide homeostasis<\/a>. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.<\/p>\n\n\n\n16.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- Excretion<\/a> is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains homeostasis<\/a>.<\/li>\n
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the excretory system<\/a>.<\/li>\n
- The skin<\/a> plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of urea<\/a>, a byproduct of\u00a0protein\u00a0catabolism.<\/li>\n
- The liver<\/a> is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes bilirubin<\/a> \u2014 a waste product of hemoglobin<\/a> catabolism<\/a> \u2014 in bile. Bile then travels to the\u00a0small intestine<\/a>, and is eventually excreted in feces<\/a> by the large intestine<\/a>.<\/li>\n
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in bile<\/a>.<\/li>\n
- The lungs<\/a> are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0cellular respiration<\/a>\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\n
- The paired kidneys<\/a> are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called nephrons<\/a>\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine<\/a>. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n16.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- What is excretion, and what is its significance?<\/li>\n
- \n\n
Excretory Organs<\/h3>\r\n<\/div>\r\nOrgans of excretion include the [pb_glossary id=\"3521\"]skin[\/pb_glossary], [pb_glossary id=\"2989\"]liver[\/pb_glossary], [pb_glossary id=\"4560\"]large intestine[\/pb_glossary], [pb_glossary id=\"2990\"]lungs[\/pb_glossary], and [pb_glossary id=\"2988\"]kidneys[\/pb_glossary] (see Figure 16.2.2). Together, these organs make up the [pb_glossary id=\"5999\"]excretory system[\/pb_glossary]<\/strong>.\u00a0They all\u00a0excrete wastes, but they don\u2019t work together in the same way that organs do in most other body systems. Each of the excretory organs \u201cdoes its own thing\u201d more-or-less independently of the others, but all are necessary to successfully excrete the full range of wastes from the\u00a0human body.\r\n\r\n[h5p id=\"628\"]\r\n\r\n\r\nFigure 16.2.2 Internal organs of excretion are identified in this illustration. They include the skin, liver, large intestine, lungs, and kidneys.<\/em>\r\n\r\n<\/div>\r\nSkin<\/h2>\r\n[caption id=\"attachment_4712\" align=\"alignright\" width=\"421\"] Figure 16.2.3 The purpose of sweat production is mainly to cool the body and prevent overheating, but it also contributes to excretion.<\/em>[\/caption]\r\n\r\nThe [pb_glossary id=\"3521\"]skin[\/pb_glossary] is part of the integumentary system, but it also plays a role in excretion through the production of [pb_glossary id=\"4711\"]sweat[\/pb_glossary] by sweat glands in the dermis. Although the main role of sweat production is to cool the body and maintain temperature [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary], sweating also eliminates excess water and salts, as well as a small amount of urea. When sweating is copious, as in Figure 16.2.3, ingestion of salts and water may be helpful to maintain homeostasis in the body.\r\nLiver<\/h2>\r\n[caption id=\"attachment_4713\" align=\"alignleft\" width=\"333\"] Figure 16.2.4 The liver is an organ of excretion.<\/em>[\/caption]\r\n\r\nThe liver (shown in Figure 16.2.4) has numerous major functions, including secreting [pb_glossary id=\"4599\"]bile[\/pb_glossary] for digestion of lipids, synthesizing many proteins and other compounds, storing [pb_glossary id=\"327\"]glycogen[\/pb_glossary] and other substances, and secreting endocrine hormones. In addition to all of these functions, the liver is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. For example, the liver transforms [pb_glossary id=\"4707\"]ammonia[\/pb_glossary] \u2014 a poisonous by-product of protein [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] \u2014 into [pb_glossary id=\"4708\"]urea[\/pb_glossary], which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary],<\/strong>\u00a0a byproduct of [pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary] [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] that forms when red\u00a0blood\u00a0cells\u00a0die. Bile travels to the\u00a0small intestine\u00a0and is then excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the\u00a0[pb_glossary id=\"4560\"]large intestine[\/pb_glossary].\r\nLarge Intestine<\/h2>\r\nThe [pb_glossary id=\"4560\"]large intestine[\/pb_glossary] is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. The large intestine also collects wastes from throughout the body. [pb_glossary id=\"4599\"]Bile[\/pb_glossary] secreted into the gastrointestinal tract, for example, contains the waste product [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] from the liver. Bilirubin is a brown pigment that gives human [pb_glossary id=\"4636\"]feces[\/pb_glossary] its characteristic brown colour.\r\nLungs<\/h2>\r\nThe lungs are part of the respiratory system (shown in Figure 16.2.5), but they are also important organs of excretion. They are responsible for the excretion of gaseous wastes from the body. The main waste gas excreted by the lungs is carbon dioxide, which is a waste product of [pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary] in cells throughout the body. Carbon dioxide is diffused from the blood into the air in the tiny air sacs called [pb_glossary id=\"4311\"]alveoli[\/pb_glossary] in the lungs (shown in the inset diagram). By expelling carbon dioxide from the blood, the lungs help maintain acid-base [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary]. In fact, it is the pH of blood that controls the rate of breathing. Water vapor is also picked up from the lungs and other organs of the respiratory tract as the exhaled air passes over their moist linings, and the water vapor is excreted along with the carbon dioxide. Trace levels of some other waste gases are exhaled, as well.\r\n\r\n[caption id=\"attachment_8003\" align=\"aligncenter\" width=\"699\"] Figure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.[\/caption]\r\nKidneys<\/h2>\r\nThe paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0[pb_glossary id=\"4717\"]urine[\/pb_glossary]<\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0[pb_glossary id=\"4718\"]Nephrons[\/pb_glossary]<\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.\r\n\r\n[caption id=\"attachment_4719\" align=\"aligncenter\" width=\"512\"] Figure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em>[\/caption]\r\n\r\nBy producing and excreting urine, the kidneys play vital roles in body-wide [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary]. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.\r\n\r\n\r\n16.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- [pb_glossary id=\"4705\"]Excretion[\/pb_glossary] is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary].<\/li>\r\n \t
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the [pb_glossary id=\"5999\"]excretory system[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"3521\"]skin[\/pb_glossary] plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of [pb_glossary id=\"4708\"]urea[\/pb_glossary], a byproduct of\u00a0protein\u00a0catabolism.<\/li>\r\n \t
- The [pb_glossary id=\"2989\"]liver[\/pb_glossary] is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] \u2014 a waste product of [pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary] [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] \u2014 in bile. Bile then travels to the\u00a0[pb_glossary id=\"4559\"]small intestine[\/pb_glossary], and is eventually excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the [pb_glossary id=\"4560\"]large intestine[\/pb_glossary].<\/li>\r\n \t
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in [pb_glossary id=\"4599\"]bile[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"2990\"]lungs[\/pb_glossary] are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0[pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary]\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\r\n \t
- The paired [pb_glossary id=\"2988\"]kidneys[\/pb_glossary] are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called [pb_glossary id=\"4718\"]nephrons[\/pb_glossary]\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as [pb_glossary id=\"4717\"]urine[\/pb_glossary]. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is excretion, and what is its significance?<\/li>\r\n \t
- [h5p id=\"629\"]<\/li>\r\n \t
- Describe the excretory functions of the liver.<\/li>\r\n \t
- What are\u00a0the main excretory functions of the large intestine?<\/li>\r\n \t
- List organs of the urinary system.<\/li>\r\n \t
- Describe the physical states in which the wastes from the human body are excreted.<\/li>\r\n \t
- Give one example of why ridding the body of excess water is important.<\/li>\r\n \t
- What gives feces its brown colour? Why is that substance produced?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be\r\nWhy Can We Regrow A Liver (But Not A Limb)? MITK12Videos, 2015.<\/p>\r\n
https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
Are Sports Drinks Good For You? | Fit or Fiction, POPSUGAR Fitness, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be\r\n
Why do we sweat? - John Murnan, TED-Ed, 2018.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n
Attributions<\/h2>\r\nFigure 16.2.1<\/strong>\r\n\r\nChimneys\/ Kingston upon Hull, England<\/span><\/a> [photo] by Angela Baker<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\r\n\r\nFigure 16.2.2<\/strong>\r\n\r\n \t- Sweat or rain?<\/a> by Kullez<\/a> on Flickr<\/a> is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0\/).<\/li>\r\n \t
- Kidney front - white<\/a> from www.medicalgraphics.de<\/a> is used under a CC BY-ND 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nd\/4.0\/) license.<\/li>\r\n \t
- File:Liver Cirrhosis.png<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- File:Human lungs.png<\/a> by Sharanyaudupa<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- Tags: Offal Marking Medical Intestine Liver<\/a> by Elionas2<\/a> on Pixabay<\/a> is used under the Pixabay license<\/a> (https:\/\/pixabay.com\/service\/license\/).<\/li>\r\n<\/ul>\r\n<\/div>\r\nFigure 16.2.3<\/strong>\r\n\r\n\r\ngym_room_fitness_equipment_cardiovascular_exercise_elliptical_bike_cardio_training_sports_equipment_bodybuilding-825364<\/a> from Pxhere<\/a> is used under a CC0 1.0<\/a> Universal public domain dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/).\r\n\r\nFigure 16.2.4<\/strong>\r\n\r\nTags: Liver Organ Anatomy<\/a> by zachvanstone8<\/a> on Pixabay<\/a> is used under the Pixabay License<\/a> (https:\/\/pixabay.com\/service\/license\/).\r\n\r\nFigure 16.2.5<\/strong>\r\n\r\nLung_and_diaphragm<\/a> by Terese Winslow\/ National Cancer Institute<\/a> on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 16.2.6<\/strong>\r\n\r\n512px-Urinary_System_(Female)<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\n\r\nReferences<\/span>\r\n
MITK12Videos. (2015, June 4). Why can we regrow a liver (but not a limb)? https:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be<\/p>\r\n
POPSUGAR Fitness. (2014, February 7). Are sports drinks good for you? | Fit or Fiction. YouTube. https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
TED-Ed. (2018, May 15). Why do we sweat? - John Murnan. YouTube. https:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be<\/p>\r\n\r\n<\/div>","rendered":"
<\/p>\nFigure 16.2.1 Chimney view.<\/em><\/figcaption><\/figure>\n\nGetting Rid of Wastes<\/h1>\n<\/div>\n
The many chimneys on these houses are one way that the inhabitants of the home get rid of the wastes they produce. The chimneys expel waste gases that are created when they burn fuel in their furnace or fireplace. Think about the other wastes that people create in their homes and how we dispose of them. Solid trash and recyclables may go to the curb in a trash can, or in a recycling bin for pick up and transport to a landfill or recycling centre. Wastewater from sinks, showers, toilets, and the washing machine goes into a main sewer pipe and out of the house to join the community\u2019s sanitary sewer system.<\/p>\n
Like a busy home, your body also produces a lot of wastes that must be eliminated. Like a home,\u00a0the way\u00a0your body gets rid of wastes depends on the nature of the waste products. Some\u00a0human body\u00a0wastes are gases, some are solids, and some are in a\u00a0liquid\u00a0state. Getting rid of body wastes is called excretion, and there are a number of different\u00a0organs of excretion in the human body.<\/p>\n
\nExcretion<\/h3>\n<\/div>\n
Excretion<\/a><\/strong>\u00a0is the process of removing wastes and excess\u00a0water\u00a0from the body. It is an essential process in all living things, and it is one of the major ways the\u00a0human body\u00a0maintains\u00a0homeostasis<\/a>. It also helps prevent damage to the body. Wastes include by-products of metabolism<\/a> \u2014 some of which are toxic \u2014 and other non-useful materials, such as used up and broken down components. Some of the specific waste products that must be excreted from the body include carbon dioxide from\u00a0cellular respiration<\/a>, ammonia<\/a> and\u00a0urea<\/a><\/strong>\u00a0from\u00a0protein\u00a0catabolism, and\u00a0uric\u00a0acid<\/strong><\/a>\u00a0from\u00a0nucleic acid\u00a0catabolism.<\/p>\n\nExcretory Organs<\/h3>\n<\/div>\n
Organs of excretion include the skin<\/a>, liver<\/a>, large intestine<\/a>, lungs<\/a>, and kidneys<\/a> (see Figure 16.2.2). Together, these organs make up the excretory system<\/a><\/strong>.\u00a0They all\u00a0excrete wastes, but they don\u2019t work together in the same way that organs do in most other body systems. Each of the excretory organs \u201cdoes its own thing\u201d more-or-less independently of the others, but all are necessary to successfully excrete the full range of wastes from the\u00a0human body.<\/p>\n\n<\/div>\n<\/div>\n\nFigure 16.2.2 Internal organs of excretion are identified in this illustration. They include the skin, liver, large intestine, lungs, and kidneys.<\/em><\/p>\n<\/div>\nSkin<\/h2>\nFigure 16.2.3 The purpose of sweat production is mainly to cool the body and prevent overheating, but it also contributes to excretion.<\/em><\/figcaption><\/figure>\nThe skin<\/a> is part of the integumentary system, but it also plays a role in excretion through the production of sweat<\/a> by sweat glands in the dermis. Although the main role of sweat production is to cool the body and maintain temperature homeostasis<\/a>, sweating also eliminates excess water and salts, as well as a small amount of urea. When sweating is copious, as in Figure 16.2.3, ingestion of salts and water may be helpful to maintain homeostasis in the body.<\/p>\nLiver<\/h2>\nFigure 16.2.4 The liver is an organ of excretion.<\/em><\/figcaption><\/figure>\nThe liver (shown in Figure 16.2.4) has numerous major functions, including secreting bile<\/a> for digestion of lipids, synthesizing many proteins and other compounds, storing glycogen and other substances, and secreting endocrine hormones. In addition to all of these functions, the liver is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. For example, the liver transforms ammonia<\/a> \u2014 a poisonous by-product of protein catabolism<\/a> \u2014 into urea<\/a>, which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein bilirubin<\/a>,<\/strong>\u00a0a byproduct of hemoglobin<\/a> catabolism<\/a> that forms when red\u00a0blood\u00a0cells\u00a0die. Bile travels to the\u00a0small intestine\u00a0and is then excreted in feces<\/a> by the\u00a0large intestine<\/a>.<\/p>\nLarge Intestine<\/h2>\n
The large intestine<\/a> is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. The large intestine also collects wastes from throughout the body. Bile<\/a> secreted into the gastrointestinal tract, for example, contains the waste product bilirubin<\/a> from the liver. Bilirubin is a brown pigment that gives human feces<\/a> its characteristic brown colour.<\/p>\nLungs<\/h2>\n
The lungs are part of the respiratory system (shown in Figure 16.2.5), but they are also important organs of excretion. They are responsible for the excretion of gaseous wastes from the body. The main waste gas excreted by the lungs is carbon dioxide, which is a waste product of cellular respiration<\/a> in cells throughout the body. Carbon dioxide is diffused from the blood into the air in the tiny air sacs called alveoli<\/a> in the lungs (shown in the inset diagram). By expelling carbon dioxide from the blood, the lungs help maintain acid-base homeostasis<\/a>. In fact, it is the pH of blood that controls the rate of breathing. Water vapor is also picked up from the lungs and other organs of the respiratory tract as the exhaled air passes over their moist linings, and the water vapor is excreted along with the carbon dioxide. Trace levels of some other waste gases are exhaled, as well.<\/p>\nFigure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.<\/figcaption><\/figure>\nKidneys<\/h2>\n
The paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0urine<\/a><\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0Nephrons<\/a><\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.<\/p>\nFigure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em><\/figcaption><\/figure>\nBy producing and excreting urine, the kidneys play vital roles in body-wide homeostasis<\/a>. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.<\/p>\n\n\n\n16.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- Excretion<\/a> is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains homeostasis<\/a>.<\/li>\n
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the excretory system<\/a>.<\/li>\n
- The skin<\/a> plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of urea<\/a>, a byproduct of\u00a0protein\u00a0catabolism.<\/li>\n
- The liver<\/a> is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes bilirubin<\/a> \u2014 a waste product of hemoglobin<\/a> catabolism<\/a> \u2014 in bile. Bile then travels to the\u00a0small intestine<\/a>, and is eventually excreted in feces<\/a> by the large intestine<\/a>.<\/li>\n
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in bile<\/a>.<\/li>\n
- The lungs<\/a> are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0cellular respiration<\/a>\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\n
- The paired kidneys<\/a> are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called nephrons<\/a>\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine<\/a>. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n16.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- What is excretion, and what is its significance?<\/li>\n
- \n\n
Skin<\/h2>\r\n[caption id=\"attachment_4712\" align=\"alignright\" width=\"421\"] Figure 16.2.3 The purpose of sweat production is mainly to cool the body and prevent overheating, but it also contributes to excretion.<\/em>[\/caption]\r\n\r\nThe [pb_glossary id=\"3521\"]skin[\/pb_glossary] is part of the integumentary system, but it also plays a role in excretion through the production of [pb_glossary id=\"4711\"]sweat[\/pb_glossary] by sweat glands in the dermis. Although the main role of sweat production is to cool the body and maintain temperature [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary], sweating also eliminates excess water and salts, as well as a small amount of urea. When sweating is copious, as in Figure 16.2.3, ingestion of salts and water may be helpful to maintain homeostasis in the body.\r\nLiver<\/h2>\r\n[caption id=\"attachment_4713\" align=\"alignleft\" width=\"333\"] Figure 16.2.4 The liver is an organ of excretion.<\/em>[\/caption]\r\n\r\nThe liver (shown in Figure 16.2.4) has numerous major functions, including secreting [pb_glossary id=\"4599\"]bile[\/pb_glossary] for digestion of lipids, synthesizing many proteins and other compounds, storing [pb_glossary id=\"327\"]glycogen[\/pb_glossary] and other substances, and secreting endocrine hormones. In addition to all of these functions, the liver is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. For example, the liver transforms [pb_glossary id=\"4707\"]ammonia[\/pb_glossary] \u2014 a poisonous by-product of protein [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] \u2014 into [pb_glossary id=\"4708\"]urea[\/pb_glossary], which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary],<\/strong>\u00a0a byproduct of [pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary] [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] that forms when red\u00a0blood\u00a0cells\u00a0die. Bile travels to the\u00a0small intestine\u00a0and is then excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the\u00a0[pb_glossary id=\"4560\"]large intestine[\/pb_glossary].\r\nLarge Intestine<\/h2>\r\nThe [pb_glossary id=\"4560\"]large intestine[\/pb_glossary] is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. The large intestine also collects wastes from throughout the body. [pb_glossary id=\"4599\"]Bile[\/pb_glossary] secreted into the gastrointestinal tract, for example, contains the waste product [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] from the liver. Bilirubin is a brown pigment that gives human [pb_glossary id=\"4636\"]feces[\/pb_glossary] its characteristic brown colour.\r\nLungs<\/h2>\r\nThe lungs are part of the respiratory system (shown in Figure 16.2.5), but they are also important organs of excretion. They are responsible for the excretion of gaseous wastes from the body. The main waste gas excreted by the lungs is carbon dioxide, which is a waste product of [pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary] in cells throughout the body. Carbon dioxide is diffused from the blood into the air in the tiny air sacs called [pb_glossary id=\"4311\"]alveoli[\/pb_glossary] in the lungs (shown in the inset diagram). By expelling carbon dioxide from the blood, the lungs help maintain acid-base [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary]. In fact, it is the pH of blood that controls the rate of breathing. Water vapor is also picked up from the lungs and other organs of the respiratory tract as the exhaled air passes over their moist linings, and the water vapor is excreted along with the carbon dioxide. Trace levels of some other waste gases are exhaled, as well.\r\n\r\n[caption id=\"attachment_8003\" align=\"aligncenter\" width=\"699\"] Figure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.[\/caption]\r\nKidneys<\/h2>\r\nThe paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0[pb_glossary id=\"4717\"]urine[\/pb_glossary]<\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0[pb_glossary id=\"4718\"]Nephrons[\/pb_glossary]<\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.\r\n\r\n[caption id=\"attachment_4719\" align=\"aligncenter\" width=\"512\"] Figure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em>[\/caption]\r\n\r\nBy producing and excreting urine, the kidneys play vital roles in body-wide [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary]. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.\r\n\r\n\r\n16.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- [pb_glossary id=\"4705\"]Excretion[\/pb_glossary] is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary].<\/li>\r\n \t
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the [pb_glossary id=\"5999\"]excretory system[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"3521\"]skin[\/pb_glossary] plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of [pb_glossary id=\"4708\"]urea[\/pb_glossary], a byproduct of\u00a0protein\u00a0catabolism.<\/li>\r\n \t
- The [pb_glossary id=\"2989\"]liver[\/pb_glossary] is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] \u2014 a waste product of [pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary] [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] \u2014 in bile. Bile then travels to the\u00a0[pb_glossary id=\"4559\"]small intestine[\/pb_glossary], and is eventually excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the [pb_glossary id=\"4560\"]large intestine[\/pb_glossary].<\/li>\r\n \t
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in [pb_glossary id=\"4599\"]bile[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"2990\"]lungs[\/pb_glossary] are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0[pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary]\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\r\n \t
- The paired [pb_glossary id=\"2988\"]kidneys[\/pb_glossary] are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called [pb_glossary id=\"4718\"]nephrons[\/pb_glossary]\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as [pb_glossary id=\"4717\"]urine[\/pb_glossary]. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is excretion, and what is its significance?<\/li>\r\n \t
- [h5p id=\"629\"]<\/li>\r\n \t
- Describe the excretory functions of the liver.<\/li>\r\n \t
- What are\u00a0the main excretory functions of the large intestine?<\/li>\r\n \t
- List organs of the urinary system.<\/li>\r\n \t
- Describe the physical states in which the wastes from the human body are excreted.<\/li>\r\n \t
- Give one example of why ridding the body of excess water is important.<\/li>\r\n \t
- What gives feces its brown colour? Why is that substance produced?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be\r\nWhy Can We Regrow A Liver (But Not A Limb)? MITK12Videos, 2015.<\/p>\r\n
https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
Are Sports Drinks Good For You? | Fit or Fiction, POPSUGAR Fitness, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be\r\n
Why do we sweat? - John Murnan, TED-Ed, 2018.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n
Attributions<\/h2>\r\nFigure 16.2.1<\/strong>\r\n\r\nChimneys\/ Kingston upon Hull, England<\/span><\/a> [photo] by Angela Baker<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\r\n\r\nFigure 16.2.2<\/strong>\r\n\r\n \t- Sweat or rain?<\/a> by Kullez<\/a> on Flickr<\/a> is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0\/).<\/li>\r\n \t
- Kidney front - white<\/a> from www.medicalgraphics.de<\/a> is used under a CC BY-ND 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nd\/4.0\/) license.<\/li>\r\n \t
- File:Liver Cirrhosis.png<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- File:Human lungs.png<\/a> by Sharanyaudupa<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- Tags: Offal Marking Medical Intestine Liver<\/a> by Elionas2<\/a> on Pixabay<\/a> is used under the Pixabay license<\/a> (https:\/\/pixabay.com\/service\/license\/).<\/li>\r\n<\/ul>\r\n<\/div>\r\nFigure 16.2.3<\/strong>\r\n\r\n\r\ngym_room_fitness_equipment_cardiovascular_exercise_elliptical_bike_cardio_training_sports_equipment_bodybuilding-825364<\/a> from Pxhere<\/a> is used under a CC0 1.0<\/a> Universal public domain dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/).\r\n\r\nFigure 16.2.4<\/strong>\r\n\r\nTags: Liver Organ Anatomy<\/a> by zachvanstone8<\/a> on Pixabay<\/a> is used under the Pixabay License<\/a> (https:\/\/pixabay.com\/service\/license\/).\r\n\r\nFigure 16.2.5<\/strong>\r\n\r\nLung_and_diaphragm<\/a> by Terese Winslow\/ National Cancer Institute<\/a> on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 16.2.6<\/strong>\r\n\r\n512px-Urinary_System_(Female)<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\n\r\nReferences<\/span>\r\n
MITK12Videos. (2015, June 4). Why can we regrow a liver (but not a limb)? https:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be<\/p>\r\n
POPSUGAR Fitness. (2014, February 7). Are sports drinks good for you? | Fit or Fiction. YouTube. https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
TED-Ed. (2018, May 15). Why do we sweat? - John Murnan. YouTube. https:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be<\/p>\r\n\r\n<\/div>","rendered":"
<\/p>\nFigure 16.2.1 Chimney view.<\/em><\/figcaption><\/figure>\n\nGetting Rid of Wastes<\/h1>\n<\/div>\n
The many chimneys on these houses are one way that the inhabitants of the home get rid of the wastes they produce. The chimneys expel waste gases that are created when they burn fuel in their furnace or fireplace. Think about the other wastes that people create in their homes and how we dispose of them. Solid trash and recyclables may go to the curb in a trash can, or in a recycling bin for pick up and transport to a landfill or recycling centre. Wastewater from sinks, showers, toilets, and the washing machine goes into a main sewer pipe and out of the house to join the community\u2019s sanitary sewer system.<\/p>\n
Like a busy home, your body also produces a lot of wastes that must be eliminated. Like a home,\u00a0the way\u00a0your body gets rid of wastes depends on the nature of the waste products. Some\u00a0human body\u00a0wastes are gases, some are solids, and some are in a\u00a0liquid\u00a0state. Getting rid of body wastes is called excretion, and there are a number of different\u00a0organs of excretion in the human body.<\/p>\n
\nExcretion<\/h3>\n<\/div>\n
Excretion<\/a><\/strong>\u00a0is the process of removing wastes and excess\u00a0water\u00a0from the body. It is an essential process in all living things, and it is one of the major ways the\u00a0human body\u00a0maintains\u00a0homeostasis<\/a>. It also helps prevent damage to the body. Wastes include by-products of metabolism<\/a> \u2014 some of which are toxic \u2014 and other non-useful materials, such as used up and broken down components. Some of the specific waste products that must be excreted from the body include carbon dioxide from\u00a0cellular respiration<\/a>, ammonia<\/a> and\u00a0urea<\/a><\/strong>\u00a0from\u00a0protein\u00a0catabolism, and\u00a0uric\u00a0acid<\/strong><\/a>\u00a0from\u00a0nucleic acid\u00a0catabolism.<\/p>\n\nExcretory Organs<\/h3>\n<\/div>\n
Organs of excretion include the skin<\/a>, liver<\/a>, large intestine<\/a>, lungs<\/a>, and kidneys<\/a> (see Figure 16.2.2). Together, these organs make up the excretory system<\/a><\/strong>.\u00a0They all\u00a0excrete wastes, but they don\u2019t work together in the same way that organs do in most other body systems. Each of the excretory organs \u201cdoes its own thing\u201d more-or-less independently of the others, but all are necessary to successfully excrete the full range of wastes from the\u00a0human body.<\/p>\n\n<\/div>\n<\/div>\n\nFigure 16.2.2 Internal organs of excretion are identified in this illustration. They include the skin, liver, large intestine, lungs, and kidneys.<\/em><\/p>\n<\/div>\nSkin<\/h2>\nFigure 16.2.3 The purpose of sweat production is mainly to cool the body and prevent overheating, but it also contributes to excretion.<\/em><\/figcaption><\/figure>\nThe skin<\/a> is part of the integumentary system, but it also plays a role in excretion through the production of sweat<\/a> by sweat glands in the dermis. Although the main role of sweat production is to cool the body and maintain temperature homeostasis<\/a>, sweating also eliminates excess water and salts, as well as a small amount of urea. When sweating is copious, as in Figure 16.2.3, ingestion of salts and water may be helpful to maintain homeostasis in the body.<\/p>\nLiver<\/h2>\nFigure 16.2.4 The liver is an organ of excretion.<\/em><\/figcaption><\/figure>\nThe liver (shown in Figure 16.2.4) has numerous major functions, including secreting bile<\/a> for digestion of lipids, synthesizing many proteins and other compounds, storing glycogen and other substances, and secreting endocrine hormones. In addition to all of these functions, the liver is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. For example, the liver transforms ammonia<\/a> \u2014 a poisonous by-product of protein catabolism<\/a> \u2014 into urea<\/a>, which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein bilirubin<\/a>,<\/strong>\u00a0a byproduct of hemoglobin<\/a> catabolism<\/a> that forms when red\u00a0blood\u00a0cells\u00a0die. Bile travels to the\u00a0small intestine\u00a0and is then excreted in feces<\/a> by the\u00a0large intestine<\/a>.<\/p>\nLarge Intestine<\/h2>\n
The large intestine<\/a> is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. The large intestine also collects wastes from throughout the body. Bile<\/a> secreted into the gastrointestinal tract, for example, contains the waste product bilirubin<\/a> from the liver. Bilirubin is a brown pigment that gives human feces<\/a> its characteristic brown colour.<\/p>\nLungs<\/h2>\n
The lungs are part of the respiratory system (shown in Figure 16.2.5), but they are also important organs of excretion. They are responsible for the excretion of gaseous wastes from the body. The main waste gas excreted by the lungs is carbon dioxide, which is a waste product of cellular respiration<\/a> in cells throughout the body. Carbon dioxide is diffused from the blood into the air in the tiny air sacs called alveoli<\/a> in the lungs (shown in the inset diagram). By expelling carbon dioxide from the blood, the lungs help maintain acid-base homeostasis<\/a>. In fact, it is the pH of blood that controls the rate of breathing. Water vapor is also picked up from the lungs and other organs of the respiratory tract as the exhaled air passes over their moist linings, and the water vapor is excreted along with the carbon dioxide. Trace levels of some other waste gases are exhaled, as well.<\/p>\nFigure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.<\/figcaption><\/figure>\nKidneys<\/h2>\n
The paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0urine<\/a><\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0Nephrons<\/a><\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.<\/p>\nFigure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em><\/figcaption><\/figure>\nBy producing and excreting urine, the kidneys play vital roles in body-wide homeostasis<\/a>. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.<\/p>\n\n\n\n16.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- Excretion<\/a> is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains homeostasis<\/a>.<\/li>\n
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the excretory system<\/a>.<\/li>\n
- The skin<\/a> plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of urea<\/a>, a byproduct of\u00a0protein\u00a0catabolism.<\/li>\n
- The liver<\/a> is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes bilirubin<\/a> \u2014 a waste product of hemoglobin<\/a> catabolism<\/a> \u2014 in bile. Bile then travels to the\u00a0small intestine<\/a>, and is eventually excreted in feces<\/a> by the large intestine<\/a>.<\/li>\n
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in bile<\/a>.<\/li>\n
- The lungs<\/a> are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0cellular respiration<\/a>\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\n
- The paired kidneys<\/a> are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called nephrons<\/a>\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine<\/a>. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n16.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- What is excretion, and what is its significance?<\/li>\n
- \n\n
Figure 16.2.4 The liver is an organ of excretion.<\/em>[\/caption]\r\n\r\nThe liver (shown in Figure 16.2.4) has numerous major functions, including secreting [pb_glossary id=\"4599\"]bile[\/pb_glossary] for digestion of lipids, synthesizing many proteins and other compounds, storing [pb_glossary id=\"327\"]glycogen[\/pb_glossary] and other substances, and secreting endocrine hormones. In addition to all of these functions, the liver is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. For example, the liver transforms [pb_glossary id=\"4707\"]ammonia[\/pb_glossary] \u2014 a poisonous by-product of protein [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] \u2014 into [pb_glossary id=\"4708\"]urea[\/pb_glossary], which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary],<\/strong>\u00a0a byproduct of [pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary] [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] that forms when red\u00a0blood\u00a0cells\u00a0die. Bile travels to the\u00a0small intestine\u00a0and is then excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the\u00a0[pb_glossary id=\"4560\"]large intestine[\/pb_glossary].\r\nLarge Intestine<\/h2>\r\nThe [pb_glossary id=\"4560\"]large intestine[\/pb_glossary] is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. The large intestine also collects wastes from throughout the body. [pb_glossary id=\"4599\"]Bile[\/pb_glossary] secreted into the gastrointestinal tract, for example, contains the waste product [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] from the liver. Bilirubin is a brown pigment that gives human [pb_glossary id=\"4636\"]feces[\/pb_glossary] its characteristic brown colour.\r\nLungs<\/h2>\r\nThe lungs are part of the respiratory system (shown in Figure 16.2.5), but they are also important organs of excretion. They are responsible for the excretion of gaseous wastes from the body. The main waste gas excreted by the lungs is carbon dioxide, which is a waste product of [pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary] in cells throughout the body. Carbon dioxide is diffused from the blood into the air in the tiny air sacs called [pb_glossary id=\"4311\"]alveoli[\/pb_glossary] in the lungs (shown in the inset diagram). By expelling carbon dioxide from the blood, the lungs help maintain acid-base [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary]. In fact, it is the pH of blood that controls the rate of breathing. Water vapor is also picked up from the lungs and other organs of the respiratory tract as the exhaled air passes over their moist linings, and the water vapor is excreted along with the carbon dioxide. Trace levels of some other waste gases are exhaled, as well.\r\n\r\n[caption id=\"attachment_8003\" align=\"aligncenter\" width=\"699\"] Figure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.[\/caption]\r\nKidneys<\/h2>\r\nThe paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0[pb_glossary id=\"4717\"]urine[\/pb_glossary]<\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0[pb_glossary id=\"4718\"]Nephrons[\/pb_glossary]<\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.\r\n\r\n[caption id=\"attachment_4719\" align=\"aligncenter\" width=\"512\"] Figure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em>[\/caption]\r\n\r\nBy producing and excreting urine, the kidneys play vital roles in body-wide [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary]. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.\r\n\r\n\r\n16.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- [pb_glossary id=\"4705\"]Excretion[\/pb_glossary] is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary].<\/li>\r\n \t
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the [pb_glossary id=\"5999\"]excretory system[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"3521\"]skin[\/pb_glossary] plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of [pb_glossary id=\"4708\"]urea[\/pb_glossary], a byproduct of\u00a0protein\u00a0catabolism.<\/li>\r\n \t
- The [pb_glossary id=\"2989\"]liver[\/pb_glossary] is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] \u2014 a waste product of [pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary] [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] \u2014 in bile. Bile then travels to the\u00a0[pb_glossary id=\"4559\"]small intestine[\/pb_glossary], and is eventually excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the [pb_glossary id=\"4560\"]large intestine[\/pb_glossary].<\/li>\r\n \t
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in [pb_glossary id=\"4599\"]bile[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"2990\"]lungs[\/pb_glossary] are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0[pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary]\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\r\n \t
- The paired [pb_glossary id=\"2988\"]kidneys[\/pb_glossary] are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called [pb_glossary id=\"4718\"]nephrons[\/pb_glossary]\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as [pb_glossary id=\"4717\"]urine[\/pb_glossary]. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is excretion, and what is its significance?<\/li>\r\n \t
- [h5p id=\"629\"]<\/li>\r\n \t
- Describe the excretory functions of the liver.<\/li>\r\n \t
- What are\u00a0the main excretory functions of the large intestine?<\/li>\r\n \t
- List organs of the urinary system.<\/li>\r\n \t
- Describe the physical states in which the wastes from the human body are excreted.<\/li>\r\n \t
- Give one example of why ridding the body of excess water is important.<\/li>\r\n \t
- What gives feces its brown colour? Why is that substance produced?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be\r\nWhy Can We Regrow A Liver (But Not A Limb)? MITK12Videos, 2015.<\/p>\r\n
https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
Are Sports Drinks Good For You? | Fit or Fiction, POPSUGAR Fitness, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be\r\n
Why do we sweat? - John Murnan, TED-Ed, 2018.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n
Attributions<\/h2>\r\nFigure 16.2.1<\/strong>\r\n\r\nChimneys\/ Kingston upon Hull, England<\/span><\/a> [photo] by Angela Baker<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\r\n\r\nFigure 16.2.2<\/strong>\r\n\r\n \t- Sweat or rain?<\/a> by Kullez<\/a> on Flickr<\/a> is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0\/).<\/li>\r\n \t
- Kidney front - white<\/a> from www.medicalgraphics.de<\/a> is used under a CC BY-ND 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nd\/4.0\/) license.<\/li>\r\n \t
- File:Liver Cirrhosis.png<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- File:Human lungs.png<\/a> by Sharanyaudupa<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- Tags: Offal Marking Medical Intestine Liver<\/a> by Elionas2<\/a> on Pixabay<\/a> is used under the Pixabay license<\/a> (https:\/\/pixabay.com\/service\/license\/).<\/li>\r\n<\/ul>\r\n<\/div>\r\nFigure 16.2.3<\/strong>\r\n\r\n\r\ngym_room_fitness_equipment_cardiovascular_exercise_elliptical_bike_cardio_training_sports_equipment_bodybuilding-825364<\/a> from Pxhere<\/a> is used under a CC0 1.0<\/a> Universal public domain dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/).\r\n\r\nFigure 16.2.4<\/strong>\r\n\r\nTags: Liver Organ Anatomy<\/a> by zachvanstone8<\/a> on Pixabay<\/a> is used under the Pixabay License<\/a> (https:\/\/pixabay.com\/service\/license\/).\r\n\r\nFigure 16.2.5<\/strong>\r\n\r\nLung_and_diaphragm<\/a> by Terese Winslow\/ National Cancer Institute<\/a> on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 16.2.6<\/strong>\r\n\r\n512px-Urinary_System_(Female)<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\n\r\nReferences<\/span>\r\n
MITK12Videos. (2015, June 4). Why can we regrow a liver (but not a limb)? https:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be<\/p>\r\n
POPSUGAR Fitness. (2014, February 7). Are sports drinks good for you? | Fit or Fiction. YouTube. https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
TED-Ed. (2018, May 15). Why do we sweat? - John Murnan. YouTube. https:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be<\/p>\r\n\r\n<\/div>","rendered":"
<\/p>\nFigure 16.2.1 Chimney view.<\/em><\/figcaption><\/figure>\n\nGetting Rid of Wastes<\/h1>\n<\/div>\n
The many chimneys on these houses are one way that the inhabitants of the home get rid of the wastes they produce. The chimneys expel waste gases that are created when they burn fuel in their furnace or fireplace. Think about the other wastes that people create in their homes and how we dispose of them. Solid trash and recyclables may go to the curb in a trash can, or in a recycling bin for pick up and transport to a landfill or recycling centre. Wastewater from sinks, showers, toilets, and the washing machine goes into a main sewer pipe and out of the house to join the community\u2019s sanitary sewer system.<\/p>\n
Like a busy home, your body also produces a lot of wastes that must be eliminated. Like a home,\u00a0the way\u00a0your body gets rid of wastes depends on the nature of the waste products. Some\u00a0human body\u00a0wastes are gases, some are solids, and some are in a\u00a0liquid\u00a0state. Getting rid of body wastes is called excretion, and there are a number of different\u00a0organs of excretion in the human body.<\/p>\n
\nExcretion<\/h3>\n<\/div>\n
Excretion<\/a><\/strong>\u00a0is the process of removing wastes and excess\u00a0water\u00a0from the body. It is an essential process in all living things, and it is one of the major ways the\u00a0human body\u00a0maintains\u00a0homeostasis<\/a>. It also helps prevent damage to the body. Wastes include by-products of metabolism<\/a> \u2014 some of which are toxic \u2014 and other non-useful materials, such as used up and broken down components. Some of the specific waste products that must be excreted from the body include carbon dioxide from\u00a0cellular respiration<\/a>, ammonia<\/a> and\u00a0urea<\/a><\/strong>\u00a0from\u00a0protein\u00a0catabolism, and\u00a0uric\u00a0acid<\/strong><\/a>\u00a0from\u00a0nucleic acid\u00a0catabolism.<\/p>\n\nExcretory Organs<\/h3>\n<\/div>\n
Organs of excretion include the skin<\/a>, liver<\/a>, large intestine<\/a>, lungs<\/a>, and kidneys<\/a> (see Figure 16.2.2). Together, these organs make up the excretory system<\/a><\/strong>.\u00a0They all\u00a0excrete wastes, but they don\u2019t work together in the same way that organs do in most other body systems. Each of the excretory organs \u201cdoes its own thing\u201d more-or-less independently of the others, but all are necessary to successfully excrete the full range of wastes from the\u00a0human body.<\/p>\n\n<\/div>\n<\/div>\n\nFigure 16.2.2 Internal organs of excretion are identified in this illustration. They include the skin, liver, large intestine, lungs, and kidneys.<\/em><\/p>\n<\/div>\nSkin<\/h2>\nFigure 16.2.3 The purpose of sweat production is mainly to cool the body and prevent overheating, but it also contributes to excretion.<\/em><\/figcaption><\/figure>\nThe skin<\/a> is part of the integumentary system, but it also plays a role in excretion through the production of sweat<\/a> by sweat glands in the dermis. Although the main role of sweat production is to cool the body and maintain temperature homeostasis<\/a>, sweating also eliminates excess water and salts, as well as a small amount of urea. When sweating is copious, as in Figure 16.2.3, ingestion of salts and water may be helpful to maintain homeostasis in the body.<\/p>\nLiver<\/h2>\nFigure 16.2.4 The liver is an organ of excretion.<\/em><\/figcaption><\/figure>\nThe liver (shown in Figure 16.2.4) has numerous major functions, including secreting bile<\/a> for digestion of lipids, synthesizing many proteins and other compounds, storing glycogen and other substances, and secreting endocrine hormones. In addition to all of these functions, the liver is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. For example, the liver transforms ammonia<\/a> \u2014 a poisonous by-product of protein catabolism<\/a> \u2014 into urea<\/a>, which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein bilirubin<\/a>,<\/strong>\u00a0a byproduct of hemoglobin<\/a> catabolism<\/a> that forms when red\u00a0blood\u00a0cells\u00a0die. Bile travels to the\u00a0small intestine\u00a0and is then excreted in feces<\/a> by the\u00a0large intestine<\/a>.<\/p>\nLarge Intestine<\/h2>\n
The large intestine<\/a> is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. The large intestine also collects wastes from throughout the body. Bile<\/a> secreted into the gastrointestinal tract, for example, contains the waste product bilirubin<\/a> from the liver. Bilirubin is a brown pigment that gives human feces<\/a> its characteristic brown colour.<\/p>\nLungs<\/h2>\n
The lungs are part of the respiratory system (shown in Figure 16.2.5), but they are also important organs of excretion. They are responsible for the excretion of gaseous wastes from the body. The main waste gas excreted by the lungs is carbon dioxide, which is a waste product of cellular respiration<\/a> in cells throughout the body. Carbon dioxide is diffused from the blood into the air in the tiny air sacs called alveoli<\/a> in the lungs (shown in the inset diagram). By expelling carbon dioxide from the blood, the lungs help maintain acid-base homeostasis<\/a>. In fact, it is the pH of blood that controls the rate of breathing. Water vapor is also picked up from the lungs and other organs of the respiratory tract as the exhaled air passes over their moist linings, and the water vapor is excreted along with the carbon dioxide. Trace levels of some other waste gases are exhaled, as well.<\/p>\nFigure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.<\/figcaption><\/figure>\nKidneys<\/h2>\n
The paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0urine<\/a><\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0Nephrons<\/a><\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.<\/p>\nFigure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em><\/figcaption><\/figure>\nBy producing and excreting urine, the kidneys play vital roles in body-wide homeostasis<\/a>. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.<\/p>\n\n\n\n16.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- Excretion<\/a> is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains homeostasis<\/a>.<\/li>\n
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the excretory system<\/a>.<\/li>\n
- The skin<\/a> plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of urea<\/a>, a byproduct of\u00a0protein\u00a0catabolism.<\/li>\n
- The liver<\/a> is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes bilirubin<\/a> \u2014 a waste product of hemoglobin<\/a> catabolism<\/a> \u2014 in bile. Bile then travels to the\u00a0small intestine<\/a>, and is eventually excreted in feces<\/a> by the large intestine<\/a>.<\/li>\n
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in bile<\/a>.<\/li>\n
- The lungs<\/a> are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0cellular respiration<\/a>\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\n
- The paired kidneys<\/a> are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called nephrons<\/a>\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine<\/a>. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n16.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- What is excretion, and what is its significance?<\/li>\n
- \n\n
Figure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.[\/caption]\r\nKidneys<\/h2>\r\nThe paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0[pb_glossary id=\"4717\"]urine[\/pb_glossary]<\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0[pb_glossary id=\"4718\"]Nephrons[\/pb_glossary]<\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.\r\n\r\n[caption id=\"attachment_4719\" align=\"aligncenter\" width=\"512\"] Figure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em>[\/caption]\r\n\r\nBy producing and excreting urine, the kidneys play vital roles in body-wide [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary]. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.\r\n\r\n\r\n16.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- [pb_glossary id=\"4705\"]Excretion[\/pb_glossary] is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary].<\/li>\r\n \t
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the [pb_glossary id=\"5999\"]excretory system[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"3521\"]skin[\/pb_glossary] plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of [pb_glossary id=\"4708\"]urea[\/pb_glossary], a byproduct of\u00a0protein\u00a0catabolism.<\/li>\r\n \t
- The [pb_glossary id=\"2989\"]liver[\/pb_glossary] is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] \u2014 a waste product of [pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary] [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] \u2014 in bile. Bile then travels to the\u00a0[pb_glossary id=\"4559\"]small intestine[\/pb_glossary], and is eventually excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the [pb_glossary id=\"4560\"]large intestine[\/pb_glossary].<\/li>\r\n \t
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in [pb_glossary id=\"4599\"]bile[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"2990\"]lungs[\/pb_glossary] are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0[pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary]\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\r\n \t
- The paired [pb_glossary id=\"2988\"]kidneys[\/pb_glossary] are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called [pb_glossary id=\"4718\"]nephrons[\/pb_glossary]\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as [pb_glossary id=\"4717\"]urine[\/pb_glossary]. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is excretion, and what is its significance?<\/li>\r\n \t
- [h5p id=\"629\"]<\/li>\r\n \t
- Describe the excretory functions of the liver.<\/li>\r\n \t
- What are\u00a0the main excretory functions of the large intestine?<\/li>\r\n \t
- List organs of the urinary system.<\/li>\r\n \t
- Describe the physical states in which the wastes from the human body are excreted.<\/li>\r\n \t
- Give one example of why ridding the body of excess water is important.<\/li>\r\n \t
- What gives feces its brown colour? Why is that substance produced?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be\r\nWhy Can We Regrow A Liver (But Not A Limb)? MITK12Videos, 2015.<\/p>\r\n
https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
Are Sports Drinks Good For You? | Fit or Fiction, POPSUGAR Fitness, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be\r\n
Why do we sweat? - John Murnan, TED-Ed, 2018.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n
Attributions<\/h2>\r\nFigure 16.2.1<\/strong>\r\n\r\nChimneys\/ Kingston upon Hull, England<\/span><\/a> [photo] by Angela Baker<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\r\n\r\nFigure 16.2.2<\/strong>\r\n\r\n \t- Sweat or rain?<\/a> by Kullez<\/a> on Flickr<\/a> is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0\/).<\/li>\r\n \t
- Kidney front - white<\/a> from www.medicalgraphics.de<\/a> is used under a CC BY-ND 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nd\/4.0\/) license.<\/li>\r\n \t
- File:Liver Cirrhosis.png<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- File:Human lungs.png<\/a> by Sharanyaudupa<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- Tags: Offal Marking Medical Intestine Liver<\/a> by Elionas2<\/a> on Pixabay<\/a> is used under the Pixabay license<\/a> (https:\/\/pixabay.com\/service\/license\/).<\/li>\r\n<\/ul>\r\n<\/div>\r\nFigure 16.2.3<\/strong>\r\n\r\n\r\ngym_room_fitness_equipment_cardiovascular_exercise_elliptical_bike_cardio_training_sports_equipment_bodybuilding-825364<\/a> from Pxhere<\/a> is used under a CC0 1.0<\/a> Universal public domain dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/).\r\n\r\nFigure 16.2.4<\/strong>\r\n\r\nTags: Liver Organ Anatomy<\/a> by zachvanstone8<\/a> on Pixabay<\/a> is used under the Pixabay License<\/a> (https:\/\/pixabay.com\/service\/license\/).\r\n\r\nFigure 16.2.5<\/strong>\r\n\r\nLung_and_diaphragm<\/a> by Terese Winslow\/ National Cancer Institute<\/a> on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 16.2.6<\/strong>\r\n\r\n512px-Urinary_System_(Female)<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\n\r\nReferences<\/span>\r\n
MITK12Videos. (2015, June 4). Why can we regrow a liver (but not a limb)? https:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be<\/p>\r\n
POPSUGAR Fitness. (2014, February 7). Are sports drinks good for you? | Fit or Fiction. YouTube. https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
TED-Ed. (2018, May 15). Why do we sweat? - John Murnan. YouTube. https:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be<\/p>\r\n\r\n<\/div>","rendered":"
<\/p>\nFigure 16.2.1 Chimney view.<\/em><\/figcaption><\/figure>\n\nGetting Rid of Wastes<\/h1>\n<\/div>\n
The many chimneys on these houses are one way that the inhabitants of the home get rid of the wastes they produce. The chimneys expel waste gases that are created when they burn fuel in their furnace or fireplace. Think about the other wastes that people create in their homes and how we dispose of them. Solid trash and recyclables may go to the curb in a trash can, or in a recycling bin for pick up and transport to a landfill or recycling centre. Wastewater from sinks, showers, toilets, and the washing machine goes into a main sewer pipe and out of the house to join the community\u2019s sanitary sewer system.<\/p>\n
Like a busy home, your body also produces a lot of wastes that must be eliminated. Like a home,\u00a0the way\u00a0your body gets rid of wastes depends on the nature of the waste products. Some\u00a0human body\u00a0wastes are gases, some are solids, and some are in a\u00a0liquid\u00a0state. Getting rid of body wastes is called excretion, and there are a number of different\u00a0organs of excretion in the human body.<\/p>\n
\nExcretion<\/h3>\n<\/div>\n
Excretion<\/a><\/strong>\u00a0is the process of removing wastes and excess\u00a0water\u00a0from the body. It is an essential process in all living things, and it is one of the major ways the\u00a0human body\u00a0maintains\u00a0homeostasis<\/a>. It also helps prevent damage to the body. Wastes include by-products of metabolism<\/a> \u2014 some of which are toxic \u2014 and other non-useful materials, such as used up and broken down components. Some of the specific waste products that must be excreted from the body include carbon dioxide from\u00a0cellular respiration<\/a>, ammonia<\/a> and\u00a0urea<\/a><\/strong>\u00a0from\u00a0protein\u00a0catabolism, and\u00a0uric\u00a0acid<\/strong><\/a>\u00a0from\u00a0nucleic acid\u00a0catabolism.<\/p>\n\nExcretory Organs<\/h3>\n<\/div>\n
Organs of excretion include the skin<\/a>, liver<\/a>, large intestine<\/a>, lungs<\/a>, and kidneys<\/a> (see Figure 16.2.2). Together, these organs make up the excretory system<\/a><\/strong>.\u00a0They all\u00a0excrete wastes, but they don\u2019t work together in the same way that organs do in most other body systems. Each of the excretory organs \u201cdoes its own thing\u201d more-or-less independently of the others, but all are necessary to successfully excrete the full range of wastes from the\u00a0human body.<\/p>\n\n<\/div>\n<\/div>\n\nFigure 16.2.2 Internal organs of excretion are identified in this illustration. They include the skin, liver, large intestine, lungs, and kidneys.<\/em><\/p>\n<\/div>\nSkin<\/h2>\nFigure 16.2.3 The purpose of sweat production is mainly to cool the body and prevent overheating, but it also contributes to excretion.<\/em><\/figcaption><\/figure>\nThe skin<\/a> is part of the integumentary system, but it also plays a role in excretion through the production of sweat<\/a> by sweat glands in the dermis. Although the main role of sweat production is to cool the body and maintain temperature homeostasis<\/a>, sweating also eliminates excess water and salts, as well as a small amount of urea. When sweating is copious, as in Figure 16.2.3, ingestion of salts and water may be helpful to maintain homeostasis in the body.<\/p>\nLiver<\/h2>\nFigure 16.2.4 The liver is an organ of excretion.<\/em><\/figcaption><\/figure>\nThe liver (shown in Figure 16.2.4) has numerous major functions, including secreting bile<\/a> for digestion of lipids, synthesizing many proteins and other compounds, storing glycogen and other substances, and secreting endocrine hormones. In addition to all of these functions, the liver is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. For example, the liver transforms ammonia<\/a> \u2014 a poisonous by-product of protein catabolism<\/a> \u2014 into urea<\/a>, which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein bilirubin<\/a>,<\/strong>\u00a0a byproduct of hemoglobin<\/a> catabolism<\/a> that forms when red\u00a0blood\u00a0cells\u00a0die. Bile travels to the\u00a0small intestine\u00a0and is then excreted in feces<\/a> by the\u00a0large intestine<\/a>.<\/p>\nLarge Intestine<\/h2>\n
The large intestine<\/a> is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. The large intestine also collects wastes from throughout the body. Bile<\/a> secreted into the gastrointestinal tract, for example, contains the waste product bilirubin<\/a> from the liver. Bilirubin is a brown pigment that gives human feces<\/a> its characteristic brown colour.<\/p>\nLungs<\/h2>\n
The lungs are part of the respiratory system (shown in Figure 16.2.5), but they are also important organs of excretion. They are responsible for the excretion of gaseous wastes from the body. The main waste gas excreted by the lungs is carbon dioxide, which is a waste product of cellular respiration<\/a> in cells throughout the body. Carbon dioxide is diffused from the blood into the air in the tiny air sacs called alveoli<\/a> in the lungs (shown in the inset diagram). By expelling carbon dioxide from the blood, the lungs help maintain acid-base homeostasis<\/a>. In fact, it is the pH of blood that controls the rate of breathing. Water vapor is also picked up from the lungs and other organs of the respiratory tract as the exhaled air passes over their moist linings, and the water vapor is excreted along with the carbon dioxide. Trace levels of some other waste gases are exhaled, as well.<\/p>\nFigure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.<\/figcaption><\/figure>\nKidneys<\/h2>\n
The paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0urine<\/a><\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0Nephrons<\/a><\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.<\/p>\nFigure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em><\/figcaption><\/figure>\nBy producing and excreting urine, the kidneys play vital roles in body-wide homeostasis<\/a>. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.<\/p>\n\n\n\n16.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- Excretion<\/a> is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains homeostasis<\/a>.<\/li>\n
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the excretory system<\/a>.<\/li>\n
- The skin<\/a> plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of urea<\/a>, a byproduct of\u00a0protein\u00a0catabolism.<\/li>\n
- The liver<\/a> is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes bilirubin<\/a> \u2014 a waste product of hemoglobin<\/a> catabolism<\/a> \u2014 in bile. Bile then travels to the\u00a0small intestine<\/a>, and is eventually excreted in feces<\/a> by the large intestine<\/a>.<\/li>\n
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in bile<\/a>.<\/li>\n
- The lungs<\/a> are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0cellular respiration<\/a>\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\n
- The paired kidneys<\/a> are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called nephrons<\/a>\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine<\/a>. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n16.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- What is excretion, and what is its significance?<\/li>\n
- \n\n
16.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- [pb_glossary id=\"4705\"]Excretion[\/pb_glossary] is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary].<\/li>\r\n \t
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the [pb_glossary id=\"5999\"]excretory system[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"3521\"]skin[\/pb_glossary] plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of [pb_glossary id=\"4708\"]urea[\/pb_glossary], a byproduct of\u00a0protein\u00a0catabolism.<\/li>\r\n \t
- The [pb_glossary id=\"2989\"]liver[\/pb_glossary] is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] \u2014 a waste product of [pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary] [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] \u2014 in bile. Bile then travels to the\u00a0[pb_glossary id=\"4559\"]small intestine[\/pb_glossary], and is eventually excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the [pb_glossary id=\"4560\"]large intestine[\/pb_glossary].<\/li>\r\n \t
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in [pb_glossary id=\"4599\"]bile[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"2990\"]lungs[\/pb_glossary] are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0[pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary]\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\r\n \t
- The paired [pb_glossary id=\"2988\"]kidneys[\/pb_glossary] are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called [pb_glossary id=\"4718\"]nephrons[\/pb_glossary]\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as [pb_glossary id=\"4717\"]urine[\/pb_glossary]. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is excretion, and what is its significance?<\/li>\r\n \t
- [h5p id=\"629\"]<\/li>\r\n \t
- Describe the excretory functions of the liver.<\/li>\r\n \t
- What are\u00a0the main excretory functions of the large intestine?<\/li>\r\n \t
- List organs of the urinary system.<\/li>\r\n \t
- Describe the physical states in which the wastes from the human body are excreted.<\/li>\r\n \t
- Give one example of why ridding the body of excess water is important.<\/li>\r\n \t
- What gives feces its brown colour? Why is that substance produced?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n16.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be\r\nWhy Can We Regrow A Liver (But Not A Limb)? MITK12Videos, 2015.<\/p>\r\n
https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
Are Sports Drinks Good For You? | Fit or Fiction, POPSUGAR Fitness, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be\r\n
Why do we sweat? - John Murnan, TED-Ed, 2018.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n
Attributions<\/h2>\r\nFigure 16.2.1<\/strong>\r\n\r\nChimneys\/ Kingston upon Hull, England<\/span><\/a> [photo] by Angela Baker<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\r\n\r\nFigure 16.2.2<\/strong>\r\n\r\n \t- Sweat or rain?<\/a> by Kullez<\/a> on Flickr<\/a> is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0\/).<\/li>\r\n \t
- Kidney front - white<\/a> from www.medicalgraphics.de<\/a> is used under a CC BY-ND 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nd\/4.0\/) license.<\/li>\r\n \t
- File:Liver Cirrhosis.png<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- File:Human lungs.png<\/a> by Sharanyaudupa<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- Tags: Offal Marking Medical Intestine Liver<\/a> by Elionas2<\/a> on Pixabay<\/a> is used under the Pixabay license<\/a> (https:\/\/pixabay.com\/service\/license\/).<\/li>\r\n<\/ul>\r\n<\/div>\r\nFigure 16.2.3<\/strong>\r\n\r\n\r\ngym_room_fitness_equipment_cardiovascular_exercise_elliptical_bike_cardio_training_sports_equipment_bodybuilding-825364<\/a> from Pxhere<\/a> is used under a CC0 1.0<\/a> Universal public domain dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/).\r\n\r\nFigure 16.2.4<\/strong>\r\n\r\nTags: Liver Organ Anatomy<\/a> by zachvanstone8<\/a> on Pixabay<\/a> is used under the Pixabay License<\/a> (https:\/\/pixabay.com\/service\/license\/).\r\n\r\nFigure 16.2.5<\/strong>\r\n\r\nLung_and_diaphragm<\/a> by Terese Winslow\/ National Cancer Institute<\/a> on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 16.2.6<\/strong>\r\n\r\n512px-Urinary_System_(Female)<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\n\r\nReferences<\/span>\r\n
MITK12Videos. (2015, June 4). Why can we regrow a liver (but not a limb)? https:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be<\/p>\r\n
POPSUGAR Fitness. (2014, February 7). Are sports drinks good for you? | Fit or Fiction. YouTube. https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
TED-Ed. (2018, May 15). Why do we sweat? - John Murnan. YouTube. https:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be<\/p>\r\n\r\n<\/div>","rendered":"
<\/p>\nFigure 16.2.1 Chimney view.<\/em><\/figcaption><\/figure>\n\nGetting Rid of Wastes<\/h1>\n<\/div>\n
The many chimneys on these houses are one way that the inhabitants of the home get rid of the wastes they produce. The chimneys expel waste gases that are created when they burn fuel in their furnace or fireplace. Think about the other wastes that people create in their homes and how we dispose of them. Solid trash and recyclables may go to the curb in a trash can, or in a recycling bin for pick up and transport to a landfill or recycling centre. Wastewater from sinks, showers, toilets, and the washing machine goes into a main sewer pipe and out of the house to join the community\u2019s sanitary sewer system.<\/p>\n
Like a busy home, your body also produces a lot of wastes that must be eliminated. Like a home,\u00a0the way\u00a0your body gets rid of wastes depends on the nature of the waste products. Some\u00a0human body\u00a0wastes are gases, some are solids, and some are in a\u00a0liquid\u00a0state. Getting rid of body wastes is called excretion, and there are a number of different\u00a0organs of excretion in the human body.<\/p>\n
\nExcretion<\/h3>\n<\/div>\n
Excretion<\/a><\/strong>\u00a0is the process of removing wastes and excess\u00a0water\u00a0from the body. It is an essential process in all living things, and it is one of the major ways the\u00a0human body\u00a0maintains\u00a0homeostasis<\/a>. It also helps prevent damage to the body. Wastes include by-products of metabolism<\/a> \u2014 some of which are toxic \u2014 and other non-useful materials, such as used up and broken down components. Some of the specific waste products that must be excreted from the body include carbon dioxide from\u00a0cellular respiration<\/a>, ammonia<\/a> and\u00a0urea<\/a><\/strong>\u00a0from\u00a0protein\u00a0catabolism, and\u00a0uric\u00a0acid<\/strong><\/a>\u00a0from\u00a0nucleic acid\u00a0catabolism.<\/p>\n\nExcretory Organs<\/h3>\n<\/div>\n
Organs of excretion include the skin<\/a>, liver<\/a>, large intestine<\/a>, lungs<\/a>, and kidneys<\/a> (see Figure 16.2.2). Together, these organs make up the excretory system<\/a><\/strong>.\u00a0They all\u00a0excrete wastes, but they don\u2019t work together in the same way that organs do in most other body systems. Each of the excretory organs \u201cdoes its own thing\u201d more-or-less independently of the others, but all are necessary to successfully excrete the full range of wastes from the\u00a0human body.<\/p>\n\n<\/div>\n<\/div>\n\nFigure 16.2.2 Internal organs of excretion are identified in this illustration. They include the skin, liver, large intestine, lungs, and kidneys.<\/em><\/p>\n<\/div>\nSkin<\/h2>\nFigure 16.2.3 The purpose of sweat production is mainly to cool the body and prevent overheating, but it also contributes to excretion.<\/em><\/figcaption><\/figure>\nThe skin<\/a> is part of the integumentary system, but it also plays a role in excretion through the production of sweat<\/a> by sweat glands in the dermis. Although the main role of sweat production is to cool the body and maintain temperature homeostasis<\/a>, sweating also eliminates excess water and salts, as well as a small amount of urea. When sweating is copious, as in Figure 16.2.3, ingestion of salts and water may be helpful to maintain homeostasis in the body.<\/p>\nLiver<\/h2>\nFigure 16.2.4 The liver is an organ of excretion.<\/em><\/figcaption><\/figure>\nThe liver (shown in Figure 16.2.4) has numerous major functions, including secreting bile<\/a> for digestion of lipids, synthesizing many proteins and other compounds, storing glycogen and other substances, and secreting endocrine hormones. In addition to all of these functions, the liver is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. For example, the liver transforms ammonia<\/a> \u2014 a poisonous by-product of protein catabolism<\/a> \u2014 into urea<\/a>, which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein bilirubin<\/a>,<\/strong>\u00a0a byproduct of hemoglobin<\/a> catabolism<\/a> that forms when red\u00a0blood\u00a0cells\u00a0die. Bile travels to the\u00a0small intestine\u00a0and is then excreted in feces<\/a> by the\u00a0large intestine<\/a>.<\/p>\nLarge Intestine<\/h2>\n
The large intestine<\/a> is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. The large intestine also collects wastes from throughout the body. Bile<\/a> secreted into the gastrointestinal tract, for example, contains the waste product bilirubin<\/a> from the liver. Bilirubin is a brown pigment that gives human feces<\/a> its characteristic brown colour.<\/p>\nLungs<\/h2>\n
The lungs are part of the respiratory system (shown in Figure 16.2.5), but they are also important organs of excretion. They are responsible for the excretion of gaseous wastes from the body. The main waste gas excreted by the lungs is carbon dioxide, which is a waste product of cellular respiration<\/a> in cells throughout the body. Carbon dioxide is diffused from the blood into the air in the tiny air sacs called alveoli<\/a> in the lungs (shown in the inset diagram). By expelling carbon dioxide from the blood, the lungs help maintain acid-base homeostasis<\/a>. In fact, it is the pH of blood that controls the rate of breathing. Water vapor is also picked up from the lungs and other organs of the respiratory tract as the exhaled air passes over their moist linings, and the water vapor is excreted along with the carbon dioxide. Trace levels of some other waste gases are exhaled, as well.<\/p>\nFigure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.<\/figcaption><\/figure>\nKidneys<\/h2>\n
The paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0urine<\/a><\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0Nephrons<\/a><\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.<\/p>\nFigure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em><\/figcaption><\/figure>\nBy producing and excreting urine, the kidneys play vital roles in body-wide homeostasis<\/a>. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.<\/p>\n\n\n\n16.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- Excretion<\/a> is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains homeostasis<\/a>.<\/li>\n
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the excretory system<\/a>.<\/li>\n
- The skin<\/a> plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of urea<\/a>, a byproduct of\u00a0protein\u00a0catabolism.<\/li>\n
- The liver<\/a> is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes bilirubin<\/a> \u2014 a waste product of hemoglobin<\/a> catabolism<\/a> \u2014 in bile. Bile then travels to the\u00a0small intestine<\/a>, and is eventually excreted in feces<\/a> by the large intestine<\/a>.<\/li>\n
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in bile<\/a>.<\/li>\n
- The lungs<\/a> are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0cellular respiration<\/a>\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\n
- The paired kidneys<\/a> are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called nephrons<\/a>\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine<\/a>. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n16.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- What is excretion, and what is its significance?<\/li>\n
- \n\n
- \r\n \t
- [pb_glossary id=\"4705\"]Excretion[\/pb_glossary] is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary].<\/li>\r\n \t
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the [pb_glossary id=\"5999\"]excretory system[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"3521\"]skin[\/pb_glossary] plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of [pb_glossary id=\"4708\"]urea[\/pb_glossary], a byproduct of\u00a0protein\u00a0catabolism.<\/li>\r\n \t
- The [pb_glossary id=\"2989\"]liver[\/pb_glossary] is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] \u2014 a waste product of [pb_glossary id=\"3556\"]hemoglobin[\/pb_glossary] [pb_glossary id=\"5721\"]catabolism[\/pb_glossary] \u2014 in bile. Bile then travels to the\u00a0[pb_glossary id=\"4559\"]small intestine[\/pb_glossary], and is eventually excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the [pb_glossary id=\"4560\"]large intestine[\/pb_glossary].<\/li>\r\n \t
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in [pb_glossary id=\"4599\"]bile[\/pb_glossary].<\/li>\r\n \t
- The [pb_glossary id=\"2990\"]lungs[\/pb_glossary] are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0[pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary]\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\r\n \t
- The paired [pb_glossary id=\"2988\"]kidneys[\/pb_glossary] are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called [pb_glossary id=\"4718\"]nephrons[\/pb_glossary]\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as [pb_glossary id=\"4717\"]urine[\/pb_glossary]. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n 16.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n
\r\n- \r\n \t
- What is excretion, and what is its significance?<\/li>\r\n \t
- [h5p id=\"629\"]<\/li>\r\n \t
- Describe the excretory functions of the liver.<\/li>\r\n \t
- What are\u00a0the main excretory functions of the large intestine?<\/li>\r\n \t
- List organs of the urinary system.<\/li>\r\n \t
- Describe the physical states in which the wastes from the human body are excreted.<\/li>\r\n \t
- Give one example of why ridding the body of excess water is important.<\/li>\r\n \t
- What gives feces its brown colour? Why is that substance produced?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n 16.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n
\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be\r\nWhy Can We Regrow A Liver (But Not A Limb)? MITK12Videos, 2015.<\/p>\r\n
https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
Are Sports Drinks Good For You? | Fit or Fiction, POPSUGAR Fitness, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be\r\n
Why do we sweat? - John Murnan, TED-Ed, 2018.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n
Attributions<\/h2>\r\nFigure 16.2.1<\/strong>\r\n\r\nChimneys\/ Kingston upon Hull, England<\/span><\/a> [photo] by Angela Baker<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\r\n\r\nFigure 16.2.2<\/strong>\r\n
- \r\n \t
- Sweat or rain?<\/a> by Kullez<\/a> on Flickr<\/a> is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0\/).<\/li>\r\n \t
- Kidney front - white<\/a> from www.medicalgraphics.de<\/a> is used under a CC BY-ND 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nd\/4.0\/) license.<\/li>\r\n \t
- File:Liver Cirrhosis.png<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- File:Human lungs.png<\/a> by Sharanyaudupa<\/a> on Wikimedia Commons is used under a CC BY SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en) license.<\/li>\r\n \t
- Tags: Offal Marking Medical Intestine Liver<\/a> by Elionas2<\/a> on Pixabay<\/a> is used under the Pixabay license<\/a> (https:\/\/pixabay.com\/service\/license\/).<\/li>\r\n<\/ul>\r\n<\/div>\r\nFigure 16.2.3<\/strong>\r\n
\r\n\r\ngym_room_fitness_equipment_cardiovascular_exercise_elliptical_bike_cardio_training_sports_equipment_bodybuilding-825364<\/a> from Pxhere<\/a> is used under a CC0 1.0<\/a> Universal public domain dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/).\r\n\r\nFigure 16.2.4<\/strong>\r\n\r\nTags: Liver Organ Anatomy<\/a> by zachvanstone8<\/a> on Pixabay<\/a> is used under the Pixabay License<\/a> (https:\/\/pixabay.com\/service\/license\/).\r\n\r\nFigure 16.2.5<\/strong>\r\n\r\nLung_and_diaphragm<\/a> by Terese Winslow\/ National Cancer Institute<\/a> on Wikimedia Commons is in the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).\r\n\r\nFigure 16.2.6<\/strong>\r\n\r\n512px-Urinary_System_(Female)<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\n\r\nReferences<\/span>\r\nMITK12Videos. (2015, June 4). Why can we regrow a liver (but not a limb)? https:\/\/www.youtube.com\/watch?v=erMCADOJcHk&feature=youtu.be<\/p>\r\n
POPSUGAR Fitness. (2014, February 7). Are sports drinks good for you? | Fit or Fiction. YouTube. https:\/\/www.youtube.com\/watch?v=SeK0zFB9yHg&feature=youtu.be<\/p>\r\n
TED-Ed. (2018, May 15). Why do we sweat? - John Murnan. YouTube. https:\/\/www.youtube.com\/watch?v=fctH_1NuqCQ&feature=youtu.be<\/p>\r\n\r\n<\/div>","rendered":"
<\/p>\n
Figure 16.2.1 Chimney view.<\/em><\/figcaption><\/figure>\n \nGetting Rid of Wastes<\/h1>\n<\/div>\n
The many chimneys on these houses are one way that the inhabitants of the home get rid of the wastes they produce. The chimneys expel waste gases that are created when they burn fuel in their furnace or fireplace. Think about the other wastes that people create in their homes and how we dispose of them. Solid trash and recyclables may go to the curb in a trash can, or in a recycling bin for pick up and transport to a landfill or recycling centre. Wastewater from sinks, showers, toilets, and the washing machine goes into a main sewer pipe and out of the house to join the community\u2019s sanitary sewer system.<\/p>\n
Like a busy home, your body also produces a lot of wastes that must be eliminated. Like a home,\u00a0the way\u00a0your body gets rid of wastes depends on the nature of the waste products. Some\u00a0human body\u00a0wastes are gases, some are solids, and some are in a\u00a0liquid\u00a0state. Getting rid of body wastes is called excretion, and there are a number of different\u00a0organs of excretion in the human body.<\/p>\n
\nExcretion<\/h3>\n<\/div>\n
Excretion<\/a><\/strong>\u00a0is the process of removing wastes and excess\u00a0water\u00a0from the body. It is an essential process in all living things, and it is one of the major ways the\u00a0human body\u00a0maintains\u00a0homeostasis<\/a>. It also helps prevent damage to the body. Wastes include by-products of metabolism<\/a> \u2014 some of which are toxic \u2014 and other non-useful materials, such as used up and broken down components. Some of the specific waste products that must be excreted from the body include carbon dioxide from\u00a0cellular respiration<\/a>, ammonia<\/a> and\u00a0urea<\/a><\/strong>\u00a0from\u00a0protein\u00a0catabolism, and\u00a0uric\u00a0acid<\/strong><\/a>\u00a0from\u00a0nucleic acid\u00a0catabolism.<\/p>\n
\nExcretory Organs<\/h3>\n<\/div>\n
Organs of excretion include the skin<\/a>, liver<\/a>, large intestine<\/a>, lungs<\/a>, and kidneys<\/a> (see Figure 16.2.2). Together, these organs make up the excretory system<\/a><\/strong>.\u00a0They all\u00a0excrete wastes, but they don\u2019t work together in the same way that organs do in most other body systems. Each of the excretory organs \u201cdoes its own thing\u201d more-or-less independently of the others, but all are necessary to successfully excrete the full range of wastes from the\u00a0human body.<\/p>\n
\n<\/div>\n<\/div>\n\nFigure 16.2.2 Internal organs of excretion are identified in this illustration. They include the skin, liver, large intestine, lungs, and kidneys.<\/em><\/p>\n<\/div>\n
Skin<\/h2>\n
Figure 16.2.3 The purpose of sweat production is mainly to cool the body and prevent overheating, but it also contributes to excretion.<\/em><\/figcaption><\/figure>\n The skin<\/a> is part of the integumentary system, but it also plays a role in excretion through the production of sweat<\/a> by sweat glands in the dermis. Although the main role of sweat production is to cool the body and maintain temperature homeostasis<\/a>, sweating also eliminates excess water and salts, as well as a small amount of urea. When sweating is copious, as in Figure 16.2.3, ingestion of salts and water may be helpful to maintain homeostasis in the body.<\/p>\n
Liver<\/h2>\n
Figure 16.2.4 The liver is an organ of excretion.<\/em><\/figcaption><\/figure>\n The liver (shown in Figure 16.2.4) has numerous major functions, including secreting bile<\/a> for digestion of lipids, synthesizing many proteins and other compounds, storing glycogen and other substances, and secreting endocrine hormones. In addition to all of these functions, the liver is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. For example, the liver transforms ammonia<\/a> \u2014 a poisonous by-product of protein catabolism<\/a> \u2014 into urea<\/a>, which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein bilirubin<\/a>,<\/strong>\u00a0a byproduct of hemoglobin<\/a> catabolism<\/a> that forms when red\u00a0blood\u00a0cells\u00a0die. Bile travels to the\u00a0small intestine\u00a0and is then excreted in feces<\/a> by the\u00a0large intestine<\/a>.<\/p>\n
Large Intestine<\/h2>\n
The large intestine<\/a> is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. The large intestine also collects wastes from throughout the body. Bile<\/a> secreted into the gastrointestinal tract, for example, contains the waste product bilirubin<\/a> from the liver. Bilirubin is a brown pigment that gives human feces<\/a> its characteristic brown colour.<\/p>\n
Lungs<\/h2>\n
The lungs are part of the respiratory system (shown in Figure 16.2.5), but they are also important organs of excretion. They are responsible for the excretion of gaseous wastes from the body. The main waste gas excreted by the lungs is carbon dioxide, which is a waste product of cellular respiration<\/a> in cells throughout the body. Carbon dioxide is diffused from the blood into the air in the tiny air sacs called alveoli<\/a> in the lungs (shown in the inset diagram). By expelling carbon dioxide from the blood, the lungs help maintain acid-base homeostasis<\/a>. In fact, it is the pH of blood that controls the rate of breathing. Water vapor is also picked up from the lungs and other organs of the respiratory tract as the exhaled air passes over their moist linings, and the water vapor is excreted along with the carbon dioxide. Trace levels of some other waste gases are exhaled, as well.<\/p>\n
Figure 16.2.5 The alveoli are the functional structures in the lungs where gaseous wastes enter the air from the blood.<\/figcaption><\/figure>\n Kidneys<\/h2>\n
The paired kidneys are often considered the main organs of excretion. The primary function of the kidneys is the elimination of excess water and wastes from the bloodstream by the production of the\u00a0liquid\u00a0waste known as\u00a0urine<\/a><\/strong>. The main structural and functional units of the kidneys are tiny structures called nephrons.\u00a0Nephrons<\/a><\/strong> filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine. As shown in Figure 16.2.6, the kidneys are organs of the urinary system, which also includes the ureters, bladder, and urethra \u2014 organs that transport, store, and eliminate urine, respectively.<\/p>\n
Figure 16.2.6 The urinary system consists of two kidneys and the structures that transport and store urine.<\/em><\/figcaption><\/figure>\n By producing and excreting urine, the kidneys play vital roles in body-wide homeostasis<\/a>. They maintain the correct volume of extracellular fluid, which is all the fluid in the body outside of cells, including the blood and lymph. The kidneys also maintain the correct balance of salts and pH in extracellular fluid. In addition, the kidneys function as endocrine glands, secreting hormones into the blood that control other body processes. You can read much more about the kidneys in section 16.4 Kidneys<\/a>.<\/p>\n
\n\n\n 16.2 Summary<\/span><\/h1>\n<\/header>\n
\n- \n
- Excretion<\/a> is the process of removing wastes and excess water from the body. It is an essential process in all living things and a major way the human body maintains homeostasis<\/a>.<\/li>\n
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the excretory system<\/a>.<\/li>\n
- The skin<\/a> plays a role in excretion through the production of sweat by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of urea<\/a>, a byproduct of\u00a0protein\u00a0catabolism.<\/li>\n
- The liver<\/a> is a very important organ of excretion. The liver breaks down many substances in the blood, including toxins. The liver also excretes bilirubin<\/a> \u2014 a waste product of hemoglobin<\/a> catabolism<\/a> \u2014 in bile. Bile then travels to the\u00a0small intestine<\/a>, and is eventually excreted in feces<\/a> by the large intestine<\/a>.<\/li>\n
- The main excretory function of the large intestine is to eliminate\u00a0solid waste that remains after food is digested and water is extracted from the indigestible matter. The large intestine also collects and excretes wastes from throughout the body, including bilirubin in bile<\/a>.<\/li>\n
- The lungs<\/a> are responsible for the excretion of gaseous wastes, primarily carbon dioxide from\u00a0cellular respiration<\/a>\u00a0in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\n
- The paired kidneys<\/a> are often considered the main organs of excretion. Their primary function is the elimination of excess water and wastes from the bloodstream by the production of urine. The kidneys contain tiny structures called nephrons<\/a>\u00a0that filter materials out of the blood, return to the blood what is needed, and excrete the rest as urine<\/a>. The kidneys are part of the\u00a0urinary system, which also includes the\u00a0ureters, urinary bladder, and urethra.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\n\n 16.2 Review Questions<\/span><\/h1>\n<\/header>\n
\n- \n
- What is excretion, and what is its significance?<\/li>\n
- \n\n
- Organs of excretion include the skin, liver, large intestine, lungs, and kidneys. All of them excrete wastes, and together they make up the excretory system<\/a>.<\/li>\n
- Kidney front - white<\/a> from www.medicalgraphics.de<\/a> is used under a CC BY-ND 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nd\/4.0\/) license.<\/li>\r\n \t
- Sweat or rain?<\/a> by Kullez<\/a> on Flickr<\/a> is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0\/).<\/li>\r\n \t
![File:Liver Cirrhosis.png<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Liver_Cirrhosis.png\"){kind=link}
![File:Human lungs.png<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Human_lungs.png\"){kind=link}
![Lung_and_diaphragm<\/a> by Terese Winslow\/](\"https:\/\/commons.wikimedia.org\/wiki\/File:Lung_and_diaphragm.jpg\"){kind=link}
![512px-Urinary_System_(Female)<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Urinary_System_(Female).png\"){kind=link}