Case Study Conclusion: Drink and Flush<\/h1>\r\n<\/div>\r\nYou are probably aware that,\u00a0because of its effects on the brain,\u00a0drinking alcohol can cause visual disturbances, slurred speech, drowsiness, impaired judgment, and loss of coordination. Although it may be less obvious, alcohol also can have serious effects on the functioning of the excretory system.\r\n\r\nAs you learned from the conversation between Talia and Shae \u2014 who were in line for the restroom at the beginning of this chapter \u2014 alcohol consumption inhibits a hormone that causes our bodies to retain water. As a result, more water is released in urine, increasing the frequency of restroom trips, as well as the risk of dehydration.\r\n\r\nWhich hormone discussed in this chapter does this? If you answered [pb_glossary id=\"5893\"]antidiuretic hormone[\/pb_glossary] (ADH; also called vasopressin) \u2014 you are correct! ADH is secreted by the\u00a0posterior [pb_glossary id=\"2938\"]pituitary gland[\/pb_glossary]\u00a0and acts on the [pb_glossary id=\"2988\"]kidneys<\/span>[\/pb_glossary]<\/span>. As you have learned, the kidneys filter the blood, reabsorb needed substances, and produce [pb_glossary id=\"4717\"]urine[\/pb_glossary]. ADH helps the body conserve water by influencing this process. ADH makes the collecting ducts in the kidneys permeable to water, allowing water molecules to be reabsorbed from the urine back into the blood through osmosis into capillaries.<\/span>\r\n\r\nAlcohol is thought to produce more dilute urine by inhibiting the release of ADH. This causes the [pb_glossary id=\"4759\"]collecting ducts<\/span>[\/pb_glossary]<\/span>\u00a0to be more impermeable to water, so less water can be reabsorbed, and more is excreted in urine. Because the volume of urine is increased, the bladder fills up more quickly, and the urge to urinate occurs more frequently. This is part of the reason why you often see a long line for the restroom in situations where many people are drinking alcohol. In addition to producing more dilute urine, simply consuming many beverages can also increase urine output.<\/span>\r\n\r\nIn most cases, moderate drinking causes only a minor and temporary effect on kidney function. However, when people consume a large quantity of alcohol in a short period of time, or abuse alcohol over long time periods, there can be serious effects on the kidney.\u00a0Binge drinking (consuming\u00a0roughly\u00a0four to five drinks in two hours) can cause a condition called \u201cacute kidney injury,\u201d a serious and sudden impairment of kidney function that requires immediate medical attention. As with the other cases of kidney failure that you learned about in this chapter, the treatment is to artificially filter the blood using [pb_glossary id=\"4783\"]hemodialysis[\/pb_glossary]. While normal kidney function may eventually return, acute kidney injury can sometimes cause long-term damage to the kidneys.\r\n\r\nIn cases where people abuse alcohol, particularly for an extended period of time, there can be many serious effects on the kidneys and other parts of the excretory system. The dehydrating effect of alcohol on the body can impair the function of many organs, including the kidneys themselves. Additionally, because of alcohol\u2019s effect on kidney function, water balance, and ion balance, chronic alcohol consumption can cause abnormalities in blood ion concentration and acid-base balance, which can be very dangerous.\r\n\r\nDrinking more than two alcoholic beverages a day can increase your risk for high blood pressure, too. As you have learned, high blood pressure is a risk factor for some kidney disorders, as well as a common cause of [pb_glossary id=\"4782\"]kidney failure[\/pb_glossary].\u00a0Drinking too much alcohol can damage the kidneys by raising blood pressure.\r\n\r\nFinally, chronic excessive consumption of alcohol can cause liver disease. The liver is an important organ of the [pb_glossary id=\"5999\"]excretory system[\/pb_glossary] that breaks down toxic substances in the blood. The liver and kidneys work together to remove wastes from the bloodstream. You may remember, for example, the liver transforms [pb_glossary id=\"4707\"]ammonia[\/pb_glossary] into [pb_glossary id=\"4708\"]urea[\/pb_glossary], which is then filtered and excreted by the kidneys. When the liver is not functioning normally, it puts added strain on the kidneys, which can result in kidney dysfunction. This association between alcohol, liver disease, and kidney dysfunction is so strong that most of the patients in Canada with both liver disease and related kidney dysfunction are alcoholics.\r\n\r\nAs you have learned, the excretory system is essential\u00a0in\u00a0removing toxic wastes from the body and regulating homeostasis. Having an occasional drink can temporarily alter these functions, but excessive alcohol exposure can seriously and permanently damage this system in many ways. Limiting alcohol consumption can help preserve the normal functioning of the excretory system, so that it can protect your health.\r\n\r\n\r\nChapter 16 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nIn this chapter you learned about the excretory system. Specifically, you learned that:\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 in which the human body maintains [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary].<\/li>\r\n \t
- Organs of the excretory system include the skin, liver, large intestine, lungs, and kidneys.<\/li>\r\n<\/ul>\r\n
\r\n \t- \r\n
\r\n \t- The [pb_glossary id=\"3521\"]skin[\/pb_glossary] plays a role in excretion through the production of [pb_glossary id=\"4711\"]sweat[\/pb_glossary] 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 protein [pb_glossary id=\"5721\"]catabolism[\/pb_glossary].<\/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 \u2014 including toxins \u2014 in the blood. The liver also excretes [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] (a waste product of hemoglobin catabolism) in bile. [pb_glossary id=\"4599\"]Bile[\/pb_glossary] then travels to the small intestine and is eventually excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the large intestine.<\/li>\r\n \t
- The main excretory function of the [pb_glossary id=\"4560\"]large intestine[\/pb_glossary] is to eliminate solid 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.<\/li>\r\n \t
- The [pb_glossary id=\"2990\"]lungs[\/pb_glossary] are responsible for the excretion of gaseous wastes \u2014 primarily carbon dioxide \u2014 from [pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary] in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The paired [pb_glossary id=\"2988\"]kidneys[\/pb_glossary]\u00a0are 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 [pb_glossary id=\"4717\"]urine[\/pb_glossary]. The kidneys filter many substances out of blood, allow the blood to reabsorb needed materials, and use the remaining materials to form urine.<\/li>\r\n<\/ul>\r\n
\r\n \t- \r\n
\r\n \t- The two bean-shaped kidneys are located high in the back of the abdominal cavity on either side of the spine. A renal artery connects each kidney with the aorta, and transports unfiltered blood to the kidney. A renal vein connects each kidney with the inferior vena cava and transports filtered blood back to the circulation.<\/li>\r\n \t
- The kidney has two main layers involved in the filtration of blood and formation of urine: the outer cortex and inner medulla. At least a million [pb_glossary id=\"4718\"]nephrons[\/pb_glossary]\u00a0\u2014 which are the tiny functional units of the kidney \u2014 span the [pb_glossary id=\"4741\"]cortex[\/pb_glossary] and [pb_glossary id=\"4742\"]medulla[\/pb_glossary]. The entire kidney is surrounded by a fibrous capsule and protective fat layers.<\/li>\r\n \t
- As blood flows through a nephron, many materials are filtered out of the blood, needed materials are returned to the blood, and the remaining materials are used to form urine.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n
\r\n \t- \r\n
\r\n \t- \r\n
\r\n \t- In each nephron, the [pb_glossary id=\"4747\"]glomerulus[\/pb_glossary] and the surrounding [pb_glossary id=\"4748\"]glomerular capsule[\/pb_glossary] form the unit that filters blood. From the glomerular capsule, the material filtered from blood (called filtrate) passes through the long [pb_glossary id=\"4749\"]renal tubule[\/pb_glossary]. As it does, some substances are reabsorbed into the blood, and other substances are secreted from the blood into the filtrate, finally forming urine. The urine empties into collecting ducts, where more water may be reabsorbed.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The kidneys are part of the urinary system, which also includes the [pb_glossary id=\"4725\"]ureters[\/pb_glossary], [pb_glossary id=\"4731\"]urinary bladder[\/pb_glossary], and [pb_glossary id=\"4732\"]urethra[\/pb_glossary]. The main function of the urinary system is to eliminate the waste products of metabolism from the body by forming and excreting urine. After urine forms in the kidneys, it is transported through the ureters to the bladder. The bladder stores the urine until urination, when urine is transported by the urethra to be excreted outside the body.<\/li>\r\n<\/ul>\r\n
\r\n \t- \r\n
\r\n \t- Besides the elimination of waste products such as urea, uric acid, excess water, and mineral ions, the urinary system has other vital functions. These include maintaining [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary] of mineral ions in extracellular fluid, regulating acid-base balance in the blood, regulating the volume of extracellular fluids, and controlling blood pressure.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n
\r\n \t- \r\n
\r\n \t- \r\n
\r\n \t- The formation of urine must be closely regulated to maintain body-wide homeostasis. Several endocrine hormones help control this function of the urinary system, including [pb_glossary id=\"5893\"]antidiuretic hormone[\/pb_glossary] secreted from the posterior pituitary gland, [pb_glossary id=\"3467\"]parathyroid hormone[\/pb_glossary] from the parathyroid glands, and [pb_glossary id=\"5881\"]aldosterone[\/pb_glossary] from the adrenal glands.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n
\r\n \t- \r\n
\r\n \t- \r\n
\r\n \t- \r\n
\r\n \t- For example, the kidneys are part of the renin-angiotensin-aldosterone system that regulates the concentration of sodium in the blood to control blood pressure. In this system, the enzyme renin secreted by the kidneys works with hormones from the liver and adrenal gland to stimulate nephrons to reabsorb more sodium and water from urine.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The kidneys also secrete endocrine hormones, including [pb_glossary id=\"4763\"]calcitriol[\/pb_glossary] \u2014 which helps control the level of calcium in the blood \u2014 and [pb_glossary id=\"4764\"]erythropoietin[\/pb_glossary], which stimulates bone marrow to produce red blood cells.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The process of urination is controlled by both the autonomic and the somatic nervous systems. The [pb_glossary id=\"5899\"]autonomic system[\/pb_glossary] causes the detrusor muscle in the bladder wall to relax as the bladder fills with urine, but conscious contraction of the detrusor muscle expels urine from the bladder during urination.<\/li>\r\n \t
- Ureters are tube-like structures that connect the kidneys with the urinary bladder. Each ureter arises at the [pb_glossary id=\"4724\"]renal pelvis[\/pb_glossary] of a kidney and travels down through the abdomen to the urinary bladder. The walls of the ureter contain [pb_glossary id=\"2982\"]smooth muscle[\/pb_glossary] that can contract to push urine through the ureter by [pb_glossary id=\"2890\"]peristalsis[\/pb_glossary]. The walls are lined with transitional epithelium that can expand and stretch.<\/li>\r\n \t
- The urinary bladder is a hollow, muscular organ that rests on the pelvic floor. It is also lined with transitional epithelium. The function of the bladder is to collect and store urine from the kidneys before the urine is eliminated through urination. Filling of the bladder triggers the autonomic nervous system to stimulate the detrusor muscle in the bladder wall to contract. This forces urine out of the bladder and into the urethra.<\/li>\r\n \t
- The urethra is a tube that connects the urinary bladder to the external urethral orifice. Somatic nerves control the [pb_glossary id=\"4627\"]sphincter[\/pb_glossary] at the distal end of the urethra. This allows the opening of the sphincter for urination to be under voluntary control.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- [pb_glossary id=\"4778\"]Diabetic nephropathy[\/pb_glossary] is a progressive kidney disease caused by damage to the capillaries in the glomeruli of the kidneys due to long-standing diabetes mellitus. Years of capillary damage may occur before symptoms first appear.<\/li>\r\n \t
- [pb_glossary id=\"4780\"]Polycystic kidney disease[\/pb_glossary] (PKD) is a genetic disorder (autosomal dominant or recessive) in which multiple abnormal cysts grow in the kidneys.<\/li>\r\n \t
- Diabetic nephropathy, PKD, or chronic hypertension may lead to kidney failure, in which the kidneys are no longer able to adequately filter metabolic wastes from the blood. Kidneys may fail to such a degree that kidney transplantation or repeated, frequent [pb_glossary id=\"4783\"]hemodialysis[\/pb_glossary] is needed to support life. In hemodialysis, the patient\u2019s blood is filtered artificially through a machine and then returned to the patient\u2019s circulation.<\/li>\r\n \t
- A kidney stone is a solid crystal that forms in a kidney from minerals in urine. A small stone may pass undetected through the ureters and the rest of the urinary tract. A larger stone may cause pain when it passes or be too large to pass, causing blockage of a ureter. Large kidney stones may be shattered with high-intensity ultrasound into pieces small enough to pass through the urinary tract, or they may be removed surgically.<\/li>\r\n \t
- A bladder infection is generally caused by bacteria that reach the bladder from the GI tract and multiply. Bladder infections are much more common in females than males because the female urethra is much shorter and closer to the anus. Treatment generally includes antibiotic drugs.<\/li>\r\n \t
- Urinary incontinence is a chronic problem of uncontrolled leakage of urine. It is very common, especially at older ages and in women. In men, urinary incontinence is usually caused by an enlarged prostate gland. In women, it is usually caused by stretching of pelvic floor muscles during childbirth (stress incontinence) or by an \u201coveractive bladder\u201d that empties without warning (urge incontinence).<\/li>\r\n<\/ul>\r\nYou have learned that,\u00a0through the removal of toxic wastes and the maintenance of homeostasis,\u00a0the excretory system protects your body. But how does your body protect itself against pathogens and other threats? Read the next chapter on the immune system to find out.\r\n\r\n<\/div>\r\n<\/div>\r\n
\r\nChapter 16 Review<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \r\n\r\n \t- [h5p id=\"635\"]<\/li>\r\n \t
- In what ways can the alveoli of the lungs be considered analogous to the nephrons of the kidney?<\/li>\r\n \t
- What is urea?\u00a0Where is urea produced, and what is it produced from?\u00a0How is urea excreted from the body?<\/li>\r\n \t
- If a person has a large kidney stone preventing\u00a0urine that has left the kidney from reaching the bladder, where do you think this kidney stone is located? Explain your answer.<\/li>\r\n \t
- As it relates to urine production, explain what is meant by \u201cExcretion = Filtration \u2013 Reabsorption + Secretion.\"<\/li>\r\n \t
- Which disease discussed in the chapter specifically affects the glomerular capillaries of the kidneys?\u00a0Where are the glomerular capillaries located within the kidneys, and what is their function?<\/li>\r\n \t
- Describe one way in which the excretory system helps maintain homeostasis in the body.<\/li>\r\n \t
- High blood pressure can both contribute to the development of kidney disorders and be a symptom of kidney disorders.\u00a0What is a kidney disorder that can be caused by high blood pressure?\u00a0What is a kidney disorder that has high blood pressure as a symptom?\u00a0How does blood pressure generally relate to the function of the kidney?<\/li>\r\n \t
- If the body is dehydrated, what do the kidneys do? What does this do to the appearance of the urine produced?<\/li>\r\n \t
- Identify three risk factors for the development of kidney stones.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
Attribution<\/h2>\r\nFigure 16.7.1<\/strong>\r\n\r\nTags: Alcohol Drink Alkolismus Bottles Glass Container<\/a> by Gerd Altmann [geralt]<\/a> on Pixabay<\/a> is used under the Pixabay License<\/a> (https:\/\/pixabay.com\/service\/license\/).\r\n\r\n<\/div>","rendered":" <\/p>\n![\"16.7.1\"](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2019\/06\/alcohol-64164_1920-2.jpg\")
Figure 16.7.1 Alcoholic affects.<\/em><\/figcaption><\/figure>\n\nCase Study Conclusion: Drink and Flush<\/h1>\n<\/div>\n
You are probably aware that,\u00a0because of its effects on the brain,\u00a0drinking alcohol can cause visual disturbances, slurred speech, drowsiness, impaired judgment, and loss of coordination. Although it may be less obvious, alcohol also can have serious effects on the functioning of the excretory system.<\/p>\n
As you learned from the conversation between Talia and Shae \u2014 who were in line for the restroom at the beginning of this chapter \u2014 alcohol consumption inhibits a hormone that causes our bodies to retain water. As a result, more water is released in urine, increasing the frequency of restroom trips, as well as the risk of dehydration.<\/p>\n
Which hormone discussed in this chapter does this? If you answered antidiuretic hormone<\/a> (ADH; also called vasopressin) \u2014 you are correct! ADH is secreted by the\u00a0posterior pituitary gland<\/a>\u00a0and acts on the kidneys<\/span><\/a><\/span>. As you have learned, the kidneys filter the blood, reabsorb needed substances, and produce urine<\/a>. ADH helps the body conserve water by influencing this process. ADH makes the collecting ducts in the kidneys permeable to water, allowing water molecules to be reabsorbed from the urine back into the blood through osmosis into capillaries.<\/span><\/p>\nAlcohol is thought to produce more dilute urine by inhibiting the release of ADH. This causes the collecting ducts<\/span><\/a><\/span>\u00a0to be more impermeable to water, so less water can be reabsorbed, and more is excreted in urine. Because the volume of urine is increased, the bladder fills up more quickly, and the urge to urinate occurs more frequently. This is part of the reason why you often see a long line for the restroom in situations where many people are drinking alcohol. In addition to producing more dilute urine, simply consuming many beverages can also increase urine output.<\/span><\/p>\nIn most cases, moderate drinking causes only a minor and temporary effect on kidney function. However, when people consume a large quantity of alcohol in a short period of time, or abuse alcohol over long time periods, there can be serious effects on the kidney.\u00a0Binge drinking (consuming\u00a0roughly\u00a0four to five drinks in two hours) can cause a condition called \u201cacute kidney injury,\u201d a serious and sudden impairment of kidney function that requires immediate medical attention. As with the other cases of kidney failure that you learned about in this chapter, the treatment is to artificially filter the blood using hemodialysis<\/a>. While normal kidney function may eventually return, acute kidney injury can sometimes cause long-term damage to the kidneys.<\/p>\nIn cases where people abuse alcohol, particularly for an extended period of time, there can be many serious effects on the kidneys and other parts of the excretory system. The dehydrating effect of alcohol on the body can impair the function of many organs, including the kidneys themselves. Additionally, because of alcohol\u2019s effect on kidney function, water balance, and ion balance, chronic alcohol consumption can cause abnormalities in blood ion concentration and acid-base balance, which can be very dangerous.<\/p>\n
Drinking more than two alcoholic beverages a day can increase your risk for high blood pressure, too. As you have learned, high blood pressure is a risk factor for some kidney disorders, as well as a common cause of kidney failure<\/a>.\u00a0Drinking too much alcohol can damage the kidneys by raising blood pressure.<\/p>\nFinally, chronic excessive consumption of alcohol can cause liver disease. The liver is an important organ of the excretory system<\/a> that breaks down toxic substances in the blood. The liver and kidneys work together to remove wastes from the bloodstream. You may remember, for example, the liver transforms ammonia<\/a> into urea<\/a>, which is then filtered and excreted by the kidneys. When the liver is not functioning normally, it puts added strain on the kidneys, which can result in kidney dysfunction. This association between alcohol, liver disease, and kidney dysfunction is so strong that most of the patients in Canada with both liver disease and related kidney dysfunction are alcoholics.<\/p>\nAs you have learned, the excretory system is essential\u00a0in\u00a0removing toxic wastes from the body and regulating homeostasis. Having an occasional drink can temporarily alter these functions, but excessive alcohol exposure can seriously and permanently damage this system in many ways. Limiting alcohol consumption can help preserve the normal functioning of the excretory system, so that it can protect your health.<\/p>\n
\n\n\nChapter 16 Summary<\/span><\/h1>\n<\/header>\n\nIn this chapter you learned about the excretory system. Specifically, you learned that:<\/p>\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 in which the human body maintains homeostasis<\/a>.<\/li>\n
- Organs of the excretory system include the skin, liver, large intestine, lungs, and kidneys.<\/li>\n<\/ul>\n
\n- \n
\n- The skin<\/a> plays a role in excretion through the production of sweat<\/a> by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of urea<\/a>, a byproduct of protein catabolism<\/a>.<\/li>\n
- The liver<\/a> is a very important organ of excretion. The liver breaks down many substances \u2014 including toxins \u2014 in the blood. The liver also excretes bilirubin<\/a> (a waste product of hemoglobin catabolism) in bile. Bile<\/a> then travels to the small intestine and is eventually excreted in feces<\/a> by the large intestine.<\/li>\n
- The main excretory function of the large intestine<\/a> is to eliminate solid 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.<\/li>\n
- The lungs<\/a> are responsible for the excretion of gaseous wastes \u2014 primarily carbon dioxide \u2014 from cellular respiration<\/a> in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\n<\/ul>\n<\/li>\n
- The paired kidneys<\/a>\u00a0are 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<\/a>. The kidneys filter many substances out of blood, allow the blood to reabsorb needed materials, and use the remaining materials to form urine.<\/li>\n<\/ul>\n
\n- \n
\n- The two bean-shaped kidneys are located high in the back of the abdominal cavity on either side of the spine. A renal artery connects each kidney with the aorta, and transports unfiltered blood to the kidney. A renal vein connects each kidney with the inferior vena cava and transports filtered blood back to the circulation.<\/li>\n
- The kidney has two main layers involved in the filtration of blood and formation of urine: the outer cortex and inner medulla. At least a million nephrons<\/a>\u00a0\u2014 which are the tiny functional units of the kidney \u2014 span the cortex<\/a> and medulla<\/a>. The entire kidney is surrounded by a fibrous capsule and protective fat layers.<\/li>\n
- As blood flows through a nephron, many materials are filtered out of the blood, needed materials are returned to the blood, and the remaining materials are used to form urine.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
\n- \n
\n- \n
\n- In each nephron, the glomerulus<\/a> and the surrounding glomerular capsule<\/a> form the unit that filters blood. From the glomerular capsule, the material filtered from blood (called filtrate) passes through the long renal tubule<\/a>. As it does, some substances are reabsorbed into the blood, and other substances are secreted from the blood into the filtrate, finally forming urine. The urine empties into collecting ducts, where more water may be reabsorbed.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n
- The kidneys are part of the urinary system, which also includes the ureters<\/a>, urinary bladder<\/a>, and urethra<\/a>. The main function of the urinary system is to eliminate the waste products of metabolism from the body by forming and excreting urine. After urine forms in the kidneys, it is transported through the ureters to the bladder. The bladder stores the urine until urination, when urine is transported by the urethra to be excreted outside the body.<\/li>\n<\/ul>\n
\n- \n
\n- Besides the elimination of waste products such as urea, uric acid, excess water, and mineral ions, the urinary system has other vital functions. These include maintaining homeostasis<\/a> of mineral ions in extracellular fluid, regulating acid-base balance in the blood, regulating the volume of extracellular fluids, and controlling blood pressure.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
\n- \n
\n- \n
\n- The formation of urine must be closely regulated to maintain body-wide homeostasis. Several endocrine hormones help control this function of the urinary system, including antidiuretic hormone<\/a> secreted from the posterior pituitary gland, parathyroid hormone<\/a> from the parathyroid glands, and aldosterone<\/a> from the adrenal glands.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
\n- \n
\n- \n
\n- \n
\n- For example, the kidneys are part of the renin-angiotensin-aldosterone system that regulates the concentration of sodium in the blood to control blood pressure. In this system, the enzyme renin secreted by the kidneys works with hormones from the liver and adrenal gland to stimulate nephrons to reabsorb more sodium and water from urine.<\/li>\n<\/ul>\n<\/li>\n
- The kidneys also secrete endocrine hormones, including calcitriol<\/a> \u2014 which helps control the level of calcium in the blood \u2014 and erythropoietin<\/a>, which stimulates bone marrow to produce red blood cells.<\/li>\n<\/ul>\n<\/li>\n
- The process of urination is controlled by both the autonomic and the somatic nervous systems. The autonomic system<\/a> causes the detrusor muscle in the bladder wall to relax as the bladder fills with urine, but conscious contraction of the detrusor muscle expels urine from the bladder during urination.<\/li>\n
- Ureters are tube-like structures that connect the kidneys with the urinary bladder. Each ureter arises at the renal pelvis<\/a> of a kidney and travels down through the abdomen to the urinary bladder. The walls of the ureter contain smooth muscle<\/a> that can contract to push urine through the ureter by peristalsis<\/a>. The walls are lined with transitional epithelium that can expand and stretch.<\/li>\n
- The urinary bladder is a hollow, muscular organ that rests on the pelvic floor. It is also lined with transitional epithelium. The function of the bladder is to collect and store urine from the kidneys before the urine is eliminated through urination. Filling of the bladder triggers the autonomic nervous system to stimulate the detrusor muscle in the bladder wall to contract. This forces urine out of the bladder and into the urethra.<\/li>\n
- The urethra is a tube that connects the urinary bladder to the external urethral orifice. Somatic nerves control the sphincter<\/a> at the distal end of the urethra. This allows the opening of the sphincter for urination to be under voluntary control.<\/li>\n<\/ul>\n<\/li>\n
- Diabetic nephropathy<\/a> is a progressive kidney disease caused by damage to the capillaries in the glomeruli of the kidneys due to long-standing diabetes mellitus. Years of capillary damage may occur before symptoms first appear.<\/li>\n
- Polycystic kidney disease<\/a> (PKD) is a genetic disorder (autosomal dominant or recessive) in which multiple abnormal cysts grow in the kidneys.<\/li>\n
- Diabetic nephropathy, PKD, or chronic hypertension may lead to kidney failure, in which the kidneys are no longer able to adequately filter metabolic wastes from the blood. Kidneys may fail to such a degree that kidney transplantation or repeated, frequent hemodialysis<\/a> is needed to support life. In hemodialysis, the patient\u2019s blood is filtered artificially through a machine and then returned to the patient\u2019s circulation.<\/li>\n
- A kidney stone is a solid crystal that forms in a kidney from minerals in urine. A small stone may pass undetected through the ureters and the rest of the urinary tract. A larger stone may cause pain when it passes or be too large to pass, causing blockage of a ureter. Large kidney stones may be shattered with high-intensity ultrasound into pieces small enough to pass through the urinary tract, or they may be removed surgically.<\/li>\n
- A bladder infection is generally caused by bacteria that reach the bladder from the GI tract and multiply. Bladder infections are much more common in females than males because the female urethra is much shorter and closer to the anus. Treatment generally includes antibiotic drugs.<\/li>\n
- Urinary incontinence is a chronic problem of uncontrolled leakage of urine. It is very common, especially at older ages and in women. In men, urinary incontinence is usually caused by an enlarged prostate gland. In women, it is usually caused by stretching of pelvic floor muscles during childbirth (stress incontinence) or by an \u201coveractive bladder\u201d that empties without warning (urge incontinence).<\/li>\n<\/ul>\n
You have learned that,\u00a0through the removal of toxic wastes and the maintenance of homeostasis,\u00a0the excretory system protects your body. But how does your body protect itself against pathogens and other threats? Read the next chapter on the immune system to find out.<\/p>\n<\/div>\n<\/div>\n
\n\nChapter 16 Review<\/span><\/h1>\n<\/header>\n\n <\/p>\n
\n- \n\n
Chapter 16 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nIn this chapter you learned about the excretory system. Specifically, you learned that:\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 in which the human body maintains [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary].<\/li>\r\n \t
- Organs of the excretory system include the skin, liver, large intestine, lungs, and kidneys.<\/li>\r\n<\/ul>\r\n
\r\n \t- \r\n
\r\n \t- The [pb_glossary id=\"3521\"]skin[\/pb_glossary] plays a role in excretion through the production of [pb_glossary id=\"4711\"]sweat[\/pb_glossary] 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 protein [pb_glossary id=\"5721\"]catabolism[\/pb_glossary].<\/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 \u2014 including toxins \u2014 in the blood. The liver also excretes [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] (a waste product of hemoglobin catabolism) in bile. [pb_glossary id=\"4599\"]Bile[\/pb_glossary] then travels to the small intestine and is eventually excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the large intestine.<\/li>\r\n \t
- The main excretory function of the [pb_glossary id=\"4560\"]large intestine[\/pb_glossary] is to eliminate solid 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.<\/li>\r\n \t
- The [pb_glossary id=\"2990\"]lungs[\/pb_glossary] are responsible for the excretion of gaseous wastes \u2014 primarily carbon dioxide \u2014 from [pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary] in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The paired [pb_glossary id=\"2988\"]kidneys[\/pb_glossary]\u00a0are 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 [pb_glossary id=\"4717\"]urine[\/pb_glossary]. The kidneys filter many substances out of blood, allow the blood to reabsorb needed materials, and use the remaining materials to form urine.<\/li>\r\n<\/ul>\r\n
\r\n \t- \r\n
\r\n \t- The two bean-shaped kidneys are located high in the back of the abdominal cavity on either side of the spine. A renal artery connects each kidney with the aorta, and transports unfiltered blood to the kidney. A renal vein connects each kidney with the inferior vena cava and transports filtered blood back to the circulation.<\/li>\r\n \t
- The kidney has two main layers involved in the filtration of blood and formation of urine: the outer cortex and inner medulla. At least a million [pb_glossary id=\"4718\"]nephrons[\/pb_glossary]\u00a0\u2014 which are the tiny functional units of the kidney \u2014 span the [pb_glossary id=\"4741\"]cortex[\/pb_glossary] and [pb_glossary id=\"4742\"]medulla[\/pb_glossary]. The entire kidney is surrounded by a fibrous capsule and protective fat layers.<\/li>\r\n \t
- As blood flows through a nephron, many materials are filtered out of the blood, needed materials are returned to the blood, and the remaining materials are used to form urine.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n
\r\n \t- \r\n
\r\n \t- \r\n
\r\n \t- In each nephron, the [pb_glossary id=\"4747\"]glomerulus[\/pb_glossary] and the surrounding [pb_glossary id=\"4748\"]glomerular capsule[\/pb_glossary] form the unit that filters blood. From the glomerular capsule, the material filtered from blood (called filtrate) passes through the long [pb_glossary id=\"4749\"]renal tubule[\/pb_glossary]. As it does, some substances are reabsorbed into the blood, and other substances are secreted from the blood into the filtrate, finally forming urine. The urine empties into collecting ducts, where more water may be reabsorbed.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The kidneys are part of the urinary system, which also includes the [pb_glossary id=\"4725\"]ureters[\/pb_glossary], [pb_glossary id=\"4731\"]urinary bladder[\/pb_glossary], and [pb_glossary id=\"4732\"]urethra[\/pb_glossary]. The main function of the urinary system is to eliminate the waste products of metabolism from the body by forming and excreting urine. After urine forms in the kidneys, it is transported through the ureters to the bladder. The bladder stores the urine until urination, when urine is transported by the urethra to be excreted outside the body.<\/li>\r\n<\/ul>\r\n
\r\n \t- \r\n
\r\n \t- Besides the elimination of waste products such as urea, uric acid, excess water, and mineral ions, the urinary system has other vital functions. These include maintaining [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary] of mineral ions in extracellular fluid, regulating acid-base balance in the blood, regulating the volume of extracellular fluids, and controlling blood pressure.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n
\r\n \t- \r\n
\r\n \t- \r\n
\r\n \t- The formation of urine must be closely regulated to maintain body-wide homeostasis. Several endocrine hormones help control this function of the urinary system, including [pb_glossary id=\"5893\"]antidiuretic hormone[\/pb_glossary] secreted from the posterior pituitary gland, [pb_glossary id=\"3467\"]parathyroid hormone[\/pb_glossary] from the parathyroid glands, and [pb_glossary id=\"5881\"]aldosterone[\/pb_glossary] from the adrenal glands.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n
\r\n \t- \r\n
\r\n \t- \r\n
\r\n \t- \r\n
\r\n \t- For example, the kidneys are part of the renin-angiotensin-aldosterone system that regulates the concentration of sodium in the blood to control blood pressure. In this system, the enzyme renin secreted by the kidneys works with hormones from the liver and adrenal gland to stimulate nephrons to reabsorb more sodium and water from urine.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The kidneys also secrete endocrine hormones, including [pb_glossary id=\"4763\"]calcitriol[\/pb_glossary] \u2014 which helps control the level of calcium in the blood \u2014 and [pb_glossary id=\"4764\"]erythropoietin[\/pb_glossary], which stimulates bone marrow to produce red blood cells.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The process of urination is controlled by both the autonomic and the somatic nervous systems. The [pb_glossary id=\"5899\"]autonomic system[\/pb_glossary] causes the detrusor muscle in the bladder wall to relax as the bladder fills with urine, but conscious contraction of the detrusor muscle expels urine from the bladder during urination.<\/li>\r\n \t
- Ureters are tube-like structures that connect the kidneys with the urinary bladder. Each ureter arises at the [pb_glossary id=\"4724\"]renal pelvis[\/pb_glossary] of a kidney and travels down through the abdomen to the urinary bladder. The walls of the ureter contain [pb_glossary id=\"2982\"]smooth muscle[\/pb_glossary] that can contract to push urine through the ureter by [pb_glossary id=\"2890\"]peristalsis[\/pb_glossary]. The walls are lined with transitional epithelium that can expand and stretch.<\/li>\r\n \t
- The urinary bladder is a hollow, muscular organ that rests on the pelvic floor. It is also lined with transitional epithelium. The function of the bladder is to collect and store urine from the kidneys before the urine is eliminated through urination. Filling of the bladder triggers the autonomic nervous system to stimulate the detrusor muscle in the bladder wall to contract. This forces urine out of the bladder and into the urethra.<\/li>\r\n \t
- The urethra is a tube that connects the urinary bladder to the external urethral orifice. Somatic nerves control the [pb_glossary id=\"4627\"]sphincter[\/pb_glossary] at the distal end of the urethra. This allows the opening of the sphincter for urination to be under voluntary control.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- [pb_glossary id=\"4778\"]Diabetic nephropathy[\/pb_glossary] is a progressive kidney disease caused by damage to the capillaries in the glomeruli of the kidneys due to long-standing diabetes mellitus. Years of capillary damage may occur before symptoms first appear.<\/li>\r\n \t
- [pb_glossary id=\"4780\"]Polycystic kidney disease[\/pb_glossary] (PKD) is a genetic disorder (autosomal dominant or recessive) in which multiple abnormal cysts grow in the kidneys.<\/li>\r\n \t
- Diabetic nephropathy, PKD, or chronic hypertension may lead to kidney failure, in which the kidneys are no longer able to adequately filter metabolic wastes from the blood. Kidneys may fail to such a degree that kidney transplantation or repeated, frequent [pb_glossary id=\"4783\"]hemodialysis[\/pb_glossary] is needed to support life. In hemodialysis, the patient\u2019s blood is filtered artificially through a machine and then returned to the patient\u2019s circulation.<\/li>\r\n \t
- A kidney stone is a solid crystal that forms in a kidney from minerals in urine. A small stone may pass undetected through the ureters and the rest of the urinary tract. A larger stone may cause pain when it passes or be too large to pass, causing blockage of a ureter. Large kidney stones may be shattered with high-intensity ultrasound into pieces small enough to pass through the urinary tract, or they may be removed surgically.<\/li>\r\n \t
- A bladder infection is generally caused by bacteria that reach the bladder from the GI tract and multiply. Bladder infections are much more common in females than males because the female urethra is much shorter and closer to the anus. Treatment generally includes antibiotic drugs.<\/li>\r\n \t
- Urinary incontinence is a chronic problem of uncontrolled leakage of urine. It is very common, especially at older ages and in women. In men, urinary incontinence is usually caused by an enlarged prostate gland. In women, it is usually caused by stretching of pelvic floor muscles during childbirth (stress incontinence) or by an \u201coveractive bladder\u201d that empties without warning (urge incontinence).<\/li>\r\n<\/ul>\r\nYou have learned that,\u00a0through the removal of toxic wastes and the maintenance of homeostasis,\u00a0the excretory system protects your body. But how does your body protect itself against pathogens and other threats? Read the next chapter on the immune system to find out.\r\n\r\n<\/div>\r\n<\/div>\r\n
\r\nChapter 16 Review<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \r\n\r\n \t- [h5p id=\"635\"]<\/li>\r\n \t
- In what ways can the alveoli of the lungs be considered analogous to the nephrons of the kidney?<\/li>\r\n \t
- What is urea?\u00a0Where is urea produced, and what is it produced from?\u00a0How is urea excreted from the body?<\/li>\r\n \t
- If a person has a large kidney stone preventing\u00a0urine that has left the kidney from reaching the bladder, where do you think this kidney stone is located? Explain your answer.<\/li>\r\n \t
- As it relates to urine production, explain what is meant by \u201cExcretion = Filtration \u2013 Reabsorption + Secretion.\"<\/li>\r\n \t
- Which disease discussed in the chapter specifically affects the glomerular capillaries of the kidneys?\u00a0Where are the glomerular capillaries located within the kidneys, and what is their function?<\/li>\r\n \t
- Describe one way in which the excretory system helps maintain homeostasis in the body.<\/li>\r\n \t
- High blood pressure can both contribute to the development of kidney disorders and be a symptom of kidney disorders.\u00a0What is a kidney disorder that can be caused by high blood pressure?\u00a0What is a kidney disorder that has high blood pressure as a symptom?\u00a0How does blood pressure generally relate to the function of the kidney?<\/li>\r\n \t
- If the body is dehydrated, what do the kidneys do? What does this do to the appearance of the urine produced?<\/li>\r\n \t
- Identify three risk factors for the development of kidney stones.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
Attribution<\/h2>\r\nFigure 16.7.1<\/strong>\r\n\r\nTags: Alcohol Drink Alkolismus Bottles Glass Container<\/a> by Gerd Altmann [geralt]<\/a> on Pixabay<\/a> is used under the Pixabay License<\/a> (https:\/\/pixabay.com\/service\/license\/).\r\n\r\n<\/div>","rendered":" <\/p>\nFigure 16.7.1 Alcoholic affects.<\/em><\/figcaption><\/figure>\n\nCase Study Conclusion: Drink and Flush<\/h1>\n<\/div>\n
You are probably aware that,\u00a0because of its effects on the brain,\u00a0drinking alcohol can cause visual disturbances, slurred speech, drowsiness, impaired judgment, and loss of coordination. Although it may be less obvious, alcohol also can have serious effects on the functioning of the excretory system.<\/p>\n
As you learned from the conversation between Talia and Shae \u2014 who were in line for the restroom at the beginning of this chapter \u2014 alcohol consumption inhibits a hormone that causes our bodies to retain water. As a result, more water is released in urine, increasing the frequency of restroom trips, as well as the risk of dehydration.<\/p>\n
Which hormone discussed in this chapter does this? If you answered antidiuretic hormone<\/a> (ADH; also called vasopressin) \u2014 you are correct! ADH is secreted by the\u00a0posterior pituitary gland<\/a>\u00a0and acts on the kidneys<\/span><\/a><\/span>. As you have learned, the kidneys filter the blood, reabsorb needed substances, and produce urine<\/a>. ADH helps the body conserve water by influencing this process. ADH makes the collecting ducts in the kidneys permeable to water, allowing water molecules to be reabsorbed from the urine back into the blood through osmosis into capillaries.<\/span><\/p>\nAlcohol is thought to produce more dilute urine by inhibiting the release of ADH. This causes the collecting ducts<\/span><\/a><\/span>\u00a0to be more impermeable to water, so less water can be reabsorbed, and more is excreted in urine. Because the volume of urine is increased, the bladder fills up more quickly, and the urge to urinate occurs more frequently. This is part of the reason why you often see a long line for the restroom in situations where many people are drinking alcohol. In addition to producing more dilute urine, simply consuming many beverages can also increase urine output.<\/span><\/p>\nIn most cases, moderate drinking causes only a minor and temporary effect on kidney function. However, when people consume a large quantity of alcohol in a short period of time, or abuse alcohol over long time periods, there can be serious effects on the kidney.\u00a0Binge drinking (consuming\u00a0roughly\u00a0four to five drinks in two hours) can cause a condition called \u201cacute kidney injury,\u201d a serious and sudden impairment of kidney function that requires immediate medical attention. As with the other cases of kidney failure that you learned about in this chapter, the treatment is to artificially filter the blood using hemodialysis<\/a>. While normal kidney function may eventually return, acute kidney injury can sometimes cause long-term damage to the kidneys.<\/p>\nIn cases where people abuse alcohol, particularly for an extended period of time, there can be many serious effects on the kidneys and other parts of the excretory system. The dehydrating effect of alcohol on the body can impair the function of many organs, including the kidneys themselves. Additionally, because of alcohol\u2019s effect on kidney function, water balance, and ion balance, chronic alcohol consumption can cause abnormalities in blood ion concentration and acid-base balance, which can be very dangerous.<\/p>\n
Drinking more than two alcoholic beverages a day can increase your risk for high blood pressure, too. As you have learned, high blood pressure is a risk factor for some kidney disorders, as well as a common cause of kidney failure<\/a>.\u00a0Drinking too much alcohol can damage the kidneys by raising blood pressure.<\/p>\nFinally, chronic excessive consumption of alcohol can cause liver disease. The liver is an important organ of the excretory system<\/a> that breaks down toxic substances in the blood. The liver and kidneys work together to remove wastes from the bloodstream. You may remember, for example, the liver transforms ammonia<\/a> into urea<\/a>, which is then filtered and excreted by the kidneys. When the liver is not functioning normally, it puts added strain on the kidneys, which can result in kidney dysfunction. This association between alcohol, liver disease, and kidney dysfunction is so strong that most of the patients in Canada with both liver disease and related kidney dysfunction are alcoholics.<\/p>\nAs you have learned, the excretory system is essential\u00a0in\u00a0removing toxic wastes from the body and regulating homeostasis. Having an occasional drink can temporarily alter these functions, but excessive alcohol exposure can seriously and permanently damage this system in many ways. Limiting alcohol consumption can help preserve the normal functioning of the excretory system, so that it can protect your health.<\/p>\n
\n\n\nChapter 16 Summary<\/span><\/h1>\n<\/header>\n\nIn this chapter you learned about the excretory system. Specifically, you learned that:<\/p>\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 in which the human body maintains homeostasis<\/a>.<\/li>\n
- Organs of the excretory system include the skin, liver, large intestine, lungs, and kidneys.<\/li>\n<\/ul>\n
\n- \n
\n- The skin<\/a> plays a role in excretion through the production of sweat<\/a> by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of urea<\/a>, a byproduct of protein catabolism<\/a>.<\/li>\n
- The liver<\/a> is a very important organ of excretion. The liver breaks down many substances \u2014 including toxins \u2014 in the blood. The liver also excretes bilirubin<\/a> (a waste product of hemoglobin catabolism) in bile. Bile<\/a> then travels to the small intestine and is eventually excreted in feces<\/a> by the large intestine.<\/li>\n
- The main excretory function of the large intestine<\/a> is to eliminate solid 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.<\/li>\n
- The lungs<\/a> are responsible for the excretion of gaseous wastes \u2014 primarily carbon dioxide \u2014 from cellular respiration<\/a> in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\n<\/ul>\n<\/li>\n
- The paired kidneys<\/a>\u00a0are 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<\/a>. The kidneys filter many substances out of blood, allow the blood to reabsorb needed materials, and use the remaining materials to form urine.<\/li>\n<\/ul>\n
\n- \n
\n- The two bean-shaped kidneys are located high in the back of the abdominal cavity on either side of the spine. A renal artery connects each kidney with the aorta, and transports unfiltered blood to the kidney. A renal vein connects each kidney with the inferior vena cava and transports filtered blood back to the circulation.<\/li>\n
- The kidney has two main layers involved in the filtration of blood and formation of urine: the outer cortex and inner medulla. At least a million nephrons<\/a>\u00a0\u2014 which are the tiny functional units of the kidney \u2014 span the cortex<\/a> and medulla<\/a>. The entire kidney is surrounded by a fibrous capsule and protective fat layers.<\/li>\n
- As blood flows through a nephron, many materials are filtered out of the blood, needed materials are returned to the blood, and the remaining materials are used to form urine.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
\n- \n
\n- \n
\n- In each nephron, the glomerulus<\/a> and the surrounding glomerular capsule<\/a> form the unit that filters blood. From the glomerular capsule, the material filtered from blood (called filtrate) passes through the long renal tubule<\/a>. As it does, some substances are reabsorbed into the blood, and other substances are secreted from the blood into the filtrate, finally forming urine. The urine empties into collecting ducts, where more water may be reabsorbed.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n
- The kidneys are part of the urinary system, which also includes the ureters<\/a>, urinary bladder<\/a>, and urethra<\/a>. The main function of the urinary system is to eliminate the waste products of metabolism from the body by forming and excreting urine. After urine forms in the kidneys, it is transported through the ureters to the bladder. The bladder stores the urine until urination, when urine is transported by the urethra to be excreted outside the body.<\/li>\n<\/ul>\n
\n- \n
\n- Besides the elimination of waste products such as urea, uric acid, excess water, and mineral ions, the urinary system has other vital functions. These include maintaining homeostasis<\/a> of mineral ions in extracellular fluid, regulating acid-base balance in the blood, regulating the volume of extracellular fluids, and controlling blood pressure.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
\n- \n
\n- \n
\n- The formation of urine must be closely regulated to maintain body-wide homeostasis. Several endocrine hormones help control this function of the urinary system, including antidiuretic hormone<\/a> secreted from the posterior pituitary gland, parathyroid hormone<\/a> from the parathyroid glands, and aldosterone<\/a> from the adrenal glands.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
\n- \n
\n- \n
\n- \n
\n- For example, the kidneys are part of the renin-angiotensin-aldosterone system that regulates the concentration of sodium in the blood to control blood pressure. In this system, the enzyme renin secreted by the kidneys works with hormones from the liver and adrenal gland to stimulate nephrons to reabsorb more sodium and water from urine.<\/li>\n<\/ul>\n<\/li>\n
- The kidneys also secrete endocrine hormones, including calcitriol<\/a> \u2014 which helps control the level of calcium in the blood \u2014 and erythropoietin<\/a>, which stimulates bone marrow to produce red blood cells.<\/li>\n<\/ul>\n<\/li>\n
- The process of urination is controlled by both the autonomic and the somatic nervous systems. The autonomic system<\/a> causes the detrusor muscle in the bladder wall to relax as the bladder fills with urine, but conscious contraction of the detrusor muscle expels urine from the bladder during urination.<\/li>\n
- Ureters are tube-like structures that connect the kidneys with the urinary bladder. Each ureter arises at the renal pelvis<\/a> of a kidney and travels down through the abdomen to the urinary bladder. The walls of the ureter contain smooth muscle<\/a> that can contract to push urine through the ureter by peristalsis<\/a>. The walls are lined with transitional epithelium that can expand and stretch.<\/li>\n
- The urinary bladder is a hollow, muscular organ that rests on the pelvic floor. It is also lined with transitional epithelium. The function of the bladder is to collect and store urine from the kidneys before the urine is eliminated through urination. Filling of the bladder triggers the autonomic nervous system to stimulate the detrusor muscle in the bladder wall to contract. This forces urine out of the bladder and into the urethra.<\/li>\n
- The urethra is a tube that connects the urinary bladder to the external urethral orifice. Somatic nerves control the sphincter<\/a> at the distal end of the urethra. This allows the opening of the sphincter for urination to be under voluntary control.<\/li>\n<\/ul>\n<\/li>\n
- Diabetic nephropathy<\/a> is a progressive kidney disease caused by damage to the capillaries in the glomeruli of the kidneys due to long-standing diabetes mellitus. Years of capillary damage may occur before symptoms first appear.<\/li>\n
- Polycystic kidney disease<\/a> (PKD) is a genetic disorder (autosomal dominant or recessive) in which multiple abnormal cysts grow in the kidneys.<\/li>\n
- Diabetic nephropathy, PKD, or chronic hypertension may lead to kidney failure, in which the kidneys are no longer able to adequately filter metabolic wastes from the blood. Kidneys may fail to such a degree that kidney transplantation or repeated, frequent hemodialysis<\/a> is needed to support life. In hemodialysis, the patient\u2019s blood is filtered artificially through a machine and then returned to the patient\u2019s circulation.<\/li>\n
- A kidney stone is a solid crystal that forms in a kidney from minerals in urine. A small stone may pass undetected through the ureters and the rest of the urinary tract. A larger stone may cause pain when it passes or be too large to pass, causing blockage of a ureter. Large kidney stones may be shattered with high-intensity ultrasound into pieces small enough to pass through the urinary tract, or they may be removed surgically.<\/li>\n
- A bladder infection is generally caused by bacteria that reach the bladder from the GI tract and multiply. Bladder infections are much more common in females than males because the female urethra is much shorter and closer to the anus. Treatment generally includes antibiotic drugs.<\/li>\n
- Urinary incontinence is a chronic problem of uncontrolled leakage of urine. It is very common, especially at older ages and in women. In men, urinary incontinence is usually caused by an enlarged prostate gland. In women, it is usually caused by stretching of pelvic floor muscles during childbirth (stress incontinence) or by an \u201coveractive bladder\u201d that empties without warning (urge incontinence).<\/li>\n<\/ul>\n
You have learned that,\u00a0through the removal of toxic wastes and the maintenance of homeostasis,\u00a0the excretory system protects your body. But how does your body protect itself against pathogens and other threats? Read the next chapter on the immune system to find out.<\/p>\n<\/div>\n<\/div>\n
\n\nChapter 16 Review<\/span><\/h1>\n<\/header>\n\n <\/p>\n
\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 in which the human body maintains [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary].<\/li>\r\n \t
- Organs of the excretory system include the skin, liver, large intestine, lungs, and kidneys.<\/li>\r\n<\/ul>\r\n
- \r\n \t
- \r\n
- \r\n \t
- The [pb_glossary id=\"3521\"]skin[\/pb_glossary] plays a role in excretion through the production of [pb_glossary id=\"4711\"]sweat[\/pb_glossary] 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 protein [pb_glossary id=\"5721\"]catabolism[\/pb_glossary].<\/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 \u2014 including toxins \u2014 in the blood. The liver also excretes [pb_glossary id=\"4715\"]bilirubin[\/pb_glossary] (a waste product of hemoglobin catabolism) in bile. [pb_glossary id=\"4599\"]Bile[\/pb_glossary] then travels to the small intestine and is eventually excreted in [pb_glossary id=\"4636\"]feces[\/pb_glossary] by the large intestine.<\/li>\r\n \t
- The main excretory function of the [pb_glossary id=\"4560\"]large intestine[\/pb_glossary] is to eliminate solid 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.<\/li>\r\n \t
- The [pb_glossary id=\"2990\"]lungs[\/pb_glossary] are responsible for the excretion of gaseous wastes \u2014 primarily carbon dioxide \u2014 from [pb_glossary id=\"5725\"]cellular respiration[\/pb_glossary] in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The paired [pb_glossary id=\"2988\"]kidneys[\/pb_glossary]\u00a0are 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 [pb_glossary id=\"4717\"]urine[\/pb_glossary]. The kidneys filter many substances out of blood, allow the blood to reabsorb needed materials, and use the remaining materials to form urine.<\/li>\r\n<\/ul>\r\n
- \r\n \t
- \r\n
- \r\n \t
- The two bean-shaped kidneys are located high in the back of the abdominal cavity on either side of the spine. A renal artery connects each kidney with the aorta, and transports unfiltered blood to the kidney. A renal vein connects each kidney with the inferior vena cava and transports filtered blood back to the circulation.<\/li>\r\n \t
- The kidney has two main layers involved in the filtration of blood and formation of urine: the outer cortex and inner medulla. At least a million [pb_glossary id=\"4718\"]nephrons[\/pb_glossary]\u00a0\u2014 which are the tiny functional units of the kidney \u2014 span the [pb_glossary id=\"4741\"]cortex[\/pb_glossary] and [pb_glossary id=\"4742\"]medulla[\/pb_glossary]. The entire kidney is surrounded by a fibrous capsule and protective fat layers.<\/li>\r\n \t
- As blood flows through a nephron, many materials are filtered out of the blood, needed materials are returned to the blood, and the remaining materials are used to form urine.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n
- \r\n \t
- \r\n
- \r\n \t
- \r\n
- \r\n \t
- In each nephron, the [pb_glossary id=\"4747\"]glomerulus[\/pb_glossary] and the surrounding [pb_glossary id=\"4748\"]glomerular capsule[\/pb_glossary] form the unit that filters blood. From the glomerular capsule, the material filtered from blood (called filtrate) passes through the long [pb_glossary id=\"4749\"]renal tubule[\/pb_glossary]. As it does, some substances are reabsorbed into the blood, and other substances are secreted from the blood into the filtrate, finally forming urine. The urine empties into collecting ducts, where more water may be reabsorbed.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The kidneys are part of the urinary system, which also includes the [pb_glossary id=\"4725\"]ureters[\/pb_glossary], [pb_glossary id=\"4731\"]urinary bladder[\/pb_glossary], and [pb_glossary id=\"4732\"]urethra[\/pb_glossary]. The main function of the urinary system is to eliminate the waste products of metabolism from the body by forming and excreting urine. After urine forms in the kidneys, it is transported through the ureters to the bladder. The bladder stores the urine until urination, when urine is transported by the urethra to be excreted outside the body.<\/li>\r\n<\/ul>\r\n
- \r\n \t
- \r\n
- \r\n \t
- Besides the elimination of waste products such as urea, uric acid, excess water, and mineral ions, the urinary system has other vital functions. These include maintaining [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary] of mineral ions in extracellular fluid, regulating acid-base balance in the blood, regulating the volume of extracellular fluids, and controlling blood pressure.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n
- \r\n \t
- \r\n
- \r\n \t
- \r\n
- \r\n \t
- The formation of urine must be closely regulated to maintain body-wide homeostasis. Several endocrine hormones help control this function of the urinary system, including [pb_glossary id=\"5893\"]antidiuretic hormone[\/pb_glossary] secreted from the posterior pituitary gland, [pb_glossary id=\"3467\"]parathyroid hormone[\/pb_glossary] from the parathyroid glands, and [pb_glossary id=\"5881\"]aldosterone[\/pb_glossary] from the adrenal glands.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n
- \r\n \t
- \r\n
- \r\n \t
- \r\n
- \r\n \t
- \r\n
- \r\n \t
- For example, the kidneys are part of the renin-angiotensin-aldosterone system that regulates the concentration of sodium in the blood to control blood pressure. In this system, the enzyme renin secreted by the kidneys works with hormones from the liver and adrenal gland to stimulate nephrons to reabsorb more sodium and water from urine.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The kidneys also secrete endocrine hormones, including [pb_glossary id=\"4763\"]calcitriol[\/pb_glossary] \u2014 which helps control the level of calcium in the blood \u2014 and [pb_glossary id=\"4764\"]erythropoietin[\/pb_glossary], which stimulates bone marrow to produce red blood cells.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The process of urination is controlled by both the autonomic and the somatic nervous systems. The [pb_glossary id=\"5899\"]autonomic system[\/pb_glossary] causes the detrusor muscle in the bladder wall to relax as the bladder fills with urine, but conscious contraction of the detrusor muscle expels urine from the bladder during urination.<\/li>\r\n \t
- Ureters are tube-like structures that connect the kidneys with the urinary bladder. Each ureter arises at the [pb_glossary id=\"4724\"]renal pelvis[\/pb_glossary] of a kidney and travels down through the abdomen to the urinary bladder. The walls of the ureter contain [pb_glossary id=\"2982\"]smooth muscle[\/pb_glossary] that can contract to push urine through the ureter by [pb_glossary id=\"2890\"]peristalsis[\/pb_glossary]. The walls are lined with transitional epithelium that can expand and stretch.<\/li>\r\n \t
- The urinary bladder is a hollow, muscular organ that rests on the pelvic floor. It is also lined with transitional epithelium. The function of the bladder is to collect and store urine from the kidneys before the urine is eliminated through urination. Filling of the bladder triggers the autonomic nervous system to stimulate the detrusor muscle in the bladder wall to contract. This forces urine out of the bladder and into the urethra.<\/li>\r\n \t
- The urethra is a tube that connects the urinary bladder to the external urethral orifice. Somatic nerves control the [pb_glossary id=\"4627\"]sphincter[\/pb_glossary] at the distal end of the urethra. This allows the opening of the sphincter for urination to be under voluntary control.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- [pb_glossary id=\"4778\"]Diabetic nephropathy[\/pb_glossary] is a progressive kidney disease caused by damage to the capillaries in the glomeruli of the kidneys due to long-standing diabetes mellitus. Years of capillary damage may occur before symptoms first appear.<\/li>\r\n \t
- [pb_glossary id=\"4780\"]Polycystic kidney disease[\/pb_glossary] (PKD) is a genetic disorder (autosomal dominant or recessive) in which multiple abnormal cysts grow in the kidneys.<\/li>\r\n \t
- Diabetic nephropathy, PKD, or chronic hypertension may lead to kidney failure, in which the kidneys are no longer able to adequately filter metabolic wastes from the blood. Kidneys may fail to such a degree that kidney transplantation or repeated, frequent [pb_glossary id=\"4783\"]hemodialysis[\/pb_glossary] is needed to support life. In hemodialysis, the patient\u2019s blood is filtered artificially through a machine and then returned to the patient\u2019s circulation.<\/li>\r\n \t
- A kidney stone is a solid crystal that forms in a kidney from minerals in urine. A small stone may pass undetected through the ureters and the rest of the urinary tract. A larger stone may cause pain when it passes or be too large to pass, causing blockage of a ureter. Large kidney stones may be shattered with high-intensity ultrasound into pieces small enough to pass through the urinary tract, or they may be removed surgically.<\/li>\r\n \t
- A bladder infection is generally caused by bacteria that reach the bladder from the GI tract and multiply. Bladder infections are much more common in females than males because the female urethra is much shorter and closer to the anus. Treatment generally includes antibiotic drugs.<\/li>\r\n \t
- Urinary incontinence is a chronic problem of uncontrolled leakage of urine. It is very common, especially at older ages and in women. In men, urinary incontinence is usually caused by an enlarged prostate gland. In women, it is usually caused by stretching of pelvic floor muscles during childbirth (stress incontinence) or by an \u201coveractive bladder\u201d that empties without warning (urge incontinence).<\/li>\r\n<\/ul>\r\nYou have learned that,\u00a0through the removal of toxic wastes and the maintenance of homeostasis,\u00a0the excretory system protects your body. But how does your body protect itself against pathogens and other threats? Read the next chapter on the immune system to find out.\r\n\r\n<\/div>\r\n<\/div>\r\n
\r\n Chapter 16 Review<\/span><\/h1>\r\n<\/header>\r\n
\r\n\r\n \r\n- \r\n \t
- [h5p id=\"635\"]<\/li>\r\n \t
- In what ways can the alveoli of the lungs be considered analogous to the nephrons of the kidney?<\/li>\r\n \t
- What is urea?\u00a0Where is urea produced, and what is it produced from?\u00a0How is urea excreted from the body?<\/li>\r\n \t
- If a person has a large kidney stone preventing\u00a0urine that has left the kidney from reaching the bladder, where do you think this kidney stone is located? Explain your answer.<\/li>\r\n \t
- As it relates to urine production, explain what is meant by \u201cExcretion = Filtration \u2013 Reabsorption + Secretion.\"<\/li>\r\n \t
- Which disease discussed in the chapter specifically affects the glomerular capillaries of the kidneys?\u00a0Where are the glomerular capillaries located within the kidneys, and what is their function?<\/li>\r\n \t
- Describe one way in which the excretory system helps maintain homeostasis in the body.<\/li>\r\n \t
- High blood pressure can both contribute to the development of kidney disorders and be a symptom of kidney disorders.\u00a0What is a kidney disorder that can be caused by high blood pressure?\u00a0What is a kidney disorder that has high blood pressure as a symptom?\u00a0How does blood pressure generally relate to the function of the kidney?<\/li>\r\n \t
- If the body is dehydrated, what do the kidneys do? What does this do to the appearance of the urine produced?<\/li>\r\n \t
- Identify three risk factors for the development of kidney stones.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
Attribution<\/h2>\r\nFigure 16.7.1<\/strong>\r\n\r\nTags: Alcohol Drink Alkolismus Bottles Glass Container<\/a> by Gerd Altmann [geralt]<\/a> on Pixabay<\/a> is used under the Pixabay License<\/a> (https:\/\/pixabay.com\/service\/license\/).\r\n\r\n<\/div>","rendered":"
<\/p>\n
Figure 16.7.1 Alcoholic affects.<\/em><\/figcaption><\/figure>\n \nCase Study Conclusion: Drink and Flush<\/h1>\n<\/div>\n
You are probably aware that,\u00a0because of its effects on the brain,\u00a0drinking alcohol can cause visual disturbances, slurred speech, drowsiness, impaired judgment, and loss of coordination. Although it may be less obvious, alcohol also can have serious effects on the functioning of the excretory system.<\/p>\n
As you learned from the conversation between Talia and Shae \u2014 who were in line for the restroom at the beginning of this chapter \u2014 alcohol consumption inhibits a hormone that causes our bodies to retain water. As a result, more water is released in urine, increasing the frequency of restroom trips, as well as the risk of dehydration.<\/p>\n
Which hormone discussed in this chapter does this? If you answered antidiuretic hormone<\/a> (ADH; also called vasopressin) \u2014 you are correct! ADH is secreted by the\u00a0posterior pituitary gland<\/a>\u00a0and acts on the kidneys<\/span><\/a><\/span>. As you have learned, the kidneys filter the blood, reabsorb needed substances, and produce urine<\/a>. ADH helps the body conserve water by influencing this process. ADH makes the collecting ducts in the kidneys permeable to water, allowing water molecules to be reabsorbed from the urine back into the blood through osmosis into capillaries.<\/span><\/p>\n
Alcohol is thought to produce more dilute urine by inhibiting the release of ADH. This causes the collecting ducts<\/span><\/a><\/span>\u00a0to be more impermeable to water, so less water can be reabsorbed, and more is excreted in urine. Because the volume of urine is increased, the bladder fills up more quickly, and the urge to urinate occurs more frequently. This is part of the reason why you often see a long line for the restroom in situations where many people are drinking alcohol. In addition to producing more dilute urine, simply consuming many beverages can also increase urine output.<\/span><\/p>\n
In most cases, moderate drinking causes only a minor and temporary effect on kidney function. However, when people consume a large quantity of alcohol in a short period of time, or abuse alcohol over long time periods, there can be serious effects on the kidney.\u00a0Binge drinking (consuming\u00a0roughly\u00a0four to five drinks in two hours) can cause a condition called \u201cacute kidney injury,\u201d a serious and sudden impairment of kidney function that requires immediate medical attention. As with the other cases of kidney failure that you learned about in this chapter, the treatment is to artificially filter the blood using hemodialysis<\/a>. While normal kidney function may eventually return, acute kidney injury can sometimes cause long-term damage to the kidneys.<\/p>\n
In cases where people abuse alcohol, particularly for an extended period of time, there can be many serious effects on the kidneys and other parts of the excretory system. The dehydrating effect of alcohol on the body can impair the function of many organs, including the kidneys themselves. Additionally, because of alcohol\u2019s effect on kidney function, water balance, and ion balance, chronic alcohol consumption can cause abnormalities in blood ion concentration and acid-base balance, which can be very dangerous.<\/p>\n
Drinking more than two alcoholic beverages a day can increase your risk for high blood pressure, too. As you have learned, high blood pressure is a risk factor for some kidney disorders, as well as a common cause of kidney failure<\/a>.\u00a0Drinking too much alcohol can damage the kidneys by raising blood pressure.<\/p>\n
Finally, chronic excessive consumption of alcohol can cause liver disease. The liver is an important organ of the excretory system<\/a> that breaks down toxic substances in the blood. The liver and kidneys work together to remove wastes from the bloodstream. You may remember, for example, the liver transforms ammonia<\/a> into urea<\/a>, which is then filtered and excreted by the kidneys. When the liver is not functioning normally, it puts added strain on the kidneys, which can result in kidney dysfunction. This association between alcohol, liver disease, and kidney dysfunction is so strong that most of the patients in Canada with both liver disease and related kidney dysfunction are alcoholics.<\/p>\n
As you have learned, the excretory system is essential\u00a0in\u00a0removing toxic wastes from the body and regulating homeostasis. Having an occasional drink can temporarily alter these functions, but excessive alcohol exposure can seriously and permanently damage this system in many ways. Limiting alcohol consumption can help preserve the normal functioning of the excretory system, so that it can protect your health.<\/p>\n
\n\n\n Chapter 16 Summary<\/span><\/h1>\n<\/header>\n
\nIn this chapter you learned about the excretory system. Specifically, you learned that:<\/p>\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 in which the human body maintains homeostasis<\/a>.<\/li>\n
- Organs of the excretory system include the skin, liver, large intestine, lungs, and kidneys.<\/li>\n<\/ul>\n
- \n
- \n
- \n
- The skin<\/a> plays a role in excretion through the production of sweat<\/a> by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of urea<\/a>, a byproduct of protein catabolism<\/a>.<\/li>\n
- The liver<\/a> is a very important organ of excretion. The liver breaks down many substances \u2014 including toxins \u2014 in the blood. The liver also excretes bilirubin<\/a> (a waste product of hemoglobin catabolism) in bile. Bile<\/a> then travels to the small intestine and is eventually excreted in feces<\/a> by the large intestine.<\/li>\n
- The main excretory function of the large intestine<\/a> is to eliminate solid 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.<\/li>\n
- The lungs<\/a> are responsible for the excretion of gaseous wastes \u2014 primarily carbon dioxide \u2014 from cellular respiration<\/a> in cells throughout the body. Exhaled air also contains water vapor and trace levels of some other waste gases.<\/li>\n<\/ul>\n<\/li>\n
- The paired kidneys<\/a>\u00a0are 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<\/a>. The kidneys filter many substances out of blood, allow the blood to reabsorb needed materials, and use the remaining materials to form urine.<\/li>\n<\/ul>\n
- \n
- \n
- \n
- The two bean-shaped kidneys are located high in the back of the abdominal cavity on either side of the spine. A renal artery connects each kidney with the aorta, and transports unfiltered blood to the kidney. A renal vein connects each kidney with the inferior vena cava and transports filtered blood back to the circulation.<\/li>\n
- The kidney has two main layers involved in the filtration of blood and formation of urine: the outer cortex and inner medulla. At least a million nephrons<\/a>\u00a0\u2014 which are the tiny functional units of the kidney \u2014 span the cortex<\/a> and medulla<\/a>. The entire kidney is surrounded by a fibrous capsule and protective fat layers.<\/li>\n
- As blood flows through a nephron, many materials are filtered out of the blood, needed materials are returned to the blood, and the remaining materials are used to form urine.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
- \n
- \n
- \n
- \n
- \n
- In each nephron, the glomerulus<\/a> and the surrounding glomerular capsule<\/a> form the unit that filters blood. From the glomerular capsule, the material filtered from blood (called filtrate) passes through the long renal tubule<\/a>. As it does, some substances are reabsorbed into the blood, and other substances are secreted from the blood into the filtrate, finally forming urine. The urine empties into collecting ducts, where more water may be reabsorbed.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n
- The kidneys are part of the urinary system, which also includes the ureters<\/a>, urinary bladder<\/a>, and urethra<\/a>. The main function of the urinary system is to eliminate the waste products of metabolism from the body by forming and excreting urine. After urine forms in the kidneys, it is transported through the ureters to the bladder. The bladder stores the urine until urination, when urine is transported by the urethra to be excreted outside the body.<\/li>\n<\/ul>\n
- \n
- \n
- \n
- Besides the elimination of waste products such as urea, uric acid, excess water, and mineral ions, the urinary system has other vital functions. These include maintaining homeostasis<\/a> of mineral ions in extracellular fluid, regulating acid-base balance in the blood, regulating the volume of extracellular fluids, and controlling blood pressure.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
- \n
- \n
- \n
- \n
- \n
- The formation of urine must be closely regulated to maintain body-wide homeostasis. Several endocrine hormones help control this function of the urinary system, including antidiuretic hormone<\/a> secreted from the posterior pituitary gland, parathyroid hormone<\/a> from the parathyroid glands, and aldosterone<\/a> from the adrenal glands.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
- \n
- \n
- \n
- \n
- \n
- \n
- \n
- For example, the kidneys are part of the renin-angiotensin-aldosterone system that regulates the concentration of sodium in the blood to control blood pressure. In this system, the enzyme renin secreted by the kidneys works with hormones from the liver and adrenal gland to stimulate nephrons to reabsorb more sodium and water from urine.<\/li>\n<\/ul>\n<\/li>\n
- The kidneys also secrete endocrine hormones, including calcitriol<\/a> \u2014 which helps control the level of calcium in the blood \u2014 and erythropoietin<\/a>, which stimulates bone marrow to produce red blood cells.<\/li>\n<\/ul>\n<\/li>\n
- The process of urination is controlled by both the autonomic and the somatic nervous systems. The autonomic system<\/a> causes the detrusor muscle in the bladder wall to relax as the bladder fills with urine, but conscious contraction of the detrusor muscle expels urine from the bladder during urination.<\/li>\n
- Ureters are tube-like structures that connect the kidneys with the urinary bladder. Each ureter arises at the renal pelvis<\/a> of a kidney and travels down through the abdomen to the urinary bladder. The walls of the ureter contain smooth muscle<\/a> that can contract to push urine through the ureter by peristalsis<\/a>. The walls are lined with transitional epithelium that can expand and stretch.<\/li>\n
- The urinary bladder is a hollow, muscular organ that rests on the pelvic floor. It is also lined with transitional epithelium. The function of the bladder is to collect and store urine from the kidneys before the urine is eliminated through urination. Filling of the bladder triggers the autonomic nervous system to stimulate the detrusor muscle in the bladder wall to contract. This forces urine out of the bladder and into the urethra.<\/li>\n
- The urethra is a tube that connects the urinary bladder to the external urethral orifice. Somatic nerves control the sphincter<\/a> at the distal end of the urethra. This allows the opening of the sphincter for urination to be under voluntary control.<\/li>\n<\/ul>\n<\/li>\n
- Diabetic nephropathy<\/a> is a progressive kidney disease caused by damage to the capillaries in the glomeruli of the kidneys due to long-standing diabetes mellitus. Years of capillary damage may occur before symptoms first appear.<\/li>\n
- Polycystic kidney disease<\/a> (PKD) is a genetic disorder (autosomal dominant or recessive) in which multiple abnormal cysts grow in the kidneys.<\/li>\n
- Diabetic nephropathy, PKD, or chronic hypertension may lead to kidney failure, in which the kidneys are no longer able to adequately filter metabolic wastes from the blood. Kidneys may fail to such a degree that kidney transplantation or repeated, frequent hemodialysis<\/a> is needed to support life. In hemodialysis, the patient\u2019s blood is filtered artificially through a machine and then returned to the patient\u2019s circulation.<\/li>\n
- A kidney stone is a solid crystal that forms in a kidney from minerals in urine. A small stone may pass undetected through the ureters and the rest of the urinary tract. A larger stone may cause pain when it passes or be too large to pass, causing blockage of a ureter. Large kidney stones may be shattered with high-intensity ultrasound into pieces small enough to pass through the urinary tract, or they may be removed surgically.<\/li>\n
- A bladder infection is generally caused by bacteria that reach the bladder from the GI tract and multiply. Bladder infections are much more common in females than males because the female urethra is much shorter and closer to the anus. Treatment generally includes antibiotic drugs.<\/li>\n
- Urinary incontinence is a chronic problem of uncontrolled leakage of urine. It is very common, especially at older ages and in women. In men, urinary incontinence is usually caused by an enlarged prostate gland. In women, it is usually caused by stretching of pelvic floor muscles during childbirth (stress incontinence) or by an \u201coveractive bladder\u201d that empties without warning (urge incontinence).<\/li>\n<\/ul>\n
You have learned that,\u00a0through the removal of toxic wastes and the maintenance of homeostasis,\u00a0the excretory system protects your body. But how does your body protect itself against pathogens and other threats? Read the next chapter on the immune system to find out.<\/p>\n<\/div>\n<\/div>\n
\n\n Chapter 16 Review<\/span><\/h1>\n<\/header>\n
\n<\/p>\n
- \n
- \n\n
- The process of urination is controlled by both the autonomic and the somatic nervous systems. The autonomic system<\/a> causes the detrusor muscle in the bladder wall to relax as the bladder fills with urine, but conscious contraction of the detrusor muscle expels urine from the bladder during urination.<\/li>\n
- \n
- \n
- \n
- The formation of urine must be closely regulated to maintain body-wide homeostasis. Several endocrine hormones help control this function of the urinary system, including antidiuretic hormone<\/a> secreted from the posterior pituitary gland, parathyroid hormone<\/a> from the parathyroid glands, and aldosterone<\/a> from the adrenal glands.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
- \n
- \n
- Besides the elimination of waste products such as urea, uric acid, excess water, and mineral ions, the urinary system has other vital functions. These include maintaining homeostasis<\/a> of mineral ions in extracellular fluid, regulating acid-base balance in the blood, regulating the volume of extracellular fluids, and controlling blood pressure.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
- The kidneys are part of the urinary system, which also includes the ureters<\/a>, urinary bladder<\/a>, and urethra<\/a>. The main function of the urinary system is to eliminate the waste products of metabolism from the body by forming and excreting urine. After urine forms in the kidneys, it is transported through the ureters to the bladder. The bladder stores the urine until urination, when urine is transported by the urethra to be excreted outside the body.<\/li>\n<\/ul>\n
- In each nephron, the glomerulus<\/a> and the surrounding glomerular capsule<\/a> form the unit that filters blood. From the glomerular capsule, the material filtered from blood (called filtrate) passes through the long renal tubule<\/a>. As it does, some substances are reabsorbed into the blood, and other substances are secreted from the blood into the filtrate, finally forming urine. The urine empties into collecting ducts, where more water may be reabsorbed.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n
- \n
- As blood flows through a nephron, many materials are filtered out of the blood, needed materials are returned to the blood, and the remaining materials are used to form urine.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
- The liver<\/a> is a very important organ of excretion. The liver breaks down many substances \u2014 including toxins \u2014 in the blood. The liver also excretes bilirubin<\/a> (a waste product of hemoglobin catabolism) in bile. Bile<\/a> then travels to the small intestine and is eventually excreted in feces<\/a> by the large intestine.<\/li>\n
- The skin<\/a> plays a role in excretion through the production of sweat<\/a> by sweat glands. Sweating eliminates excess water and salts, as well as a small amount of urea<\/a>, a byproduct of protein catabolism<\/a>.<\/li>\n
- Organs of the excretory system include the skin, liver, large intestine, lungs, and kidneys.<\/li>\n<\/ul>\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 in which the human body maintains homeostasis<\/a>.<\/li>\n
- \r\n
- \r\n
- \r\n
- The formation of urine must be closely regulated to maintain body-wide homeostasis. Several endocrine hormones help control this function of the urinary system, including [pb_glossary id=\"5893\"]antidiuretic hormone[\/pb_glossary] secreted from the posterior pituitary gland, [pb_glossary id=\"3467\"]parathyroid hormone[\/pb_glossary] from the parathyroid glands, and [pb_glossary id=\"5881\"]aldosterone[\/pb_glossary] from the adrenal glands.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n
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- Besides the elimination of waste products such as urea, uric acid, excess water, and mineral ions, the urinary system has other vital functions. These include maintaining [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary] of mineral ions in extracellular fluid, regulating acid-base balance in the blood, regulating the volume of extracellular fluids, and controlling blood pressure.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n
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