Excretory System PDF

The Excretory System Chapter 12 Waste Excretion and Internal Equilibrium Chapter 12.1 Outcomes D3.1k identify the principal structures in the excretory system; i.e., kidneys, ureters, urinary bladder, urethra D3.2k identify the major and associated structures of the nephron, including the...

The Excretory System Chapter 12 Waste Excretion and Internal Equilibrium Chapter 12.1 Outcomes D3.1k identify the principal structures in the excretory system; i.e., kidneys, ureters, urinary bladder, urethra D3.2k identify the major and associated structures of the nephron, including the glomerulus, Bowman’s capsule, tubules, loop of Henle, collecting duct, afferent and efferent arterioles, and capillary net, and explain their function in maintaining plasma compositions (i.e., water, pH, ions) D3.3k describe the function of the kidney in excreting metabolic wastes and expelling them into the environment D3.4k identify the role of antidiuretic hormone (ADH) and aldosterone in water and sodium ion reabsorption, excretion and blood pressure regulation. Waste Excretion & Internal Equilibrium The process of cellular respiration generates a number of harmful waste products that must be eliminated or excreted by the body… Lungs eliminate carbon dioxide The liver breaks down ingested toxins The kidneys eliminate these toxins and help maintain pH & water balance in the bloodstream The excretory system is therefore comprised of a number of different systems, each of which work to eliminate different types of waste from the body…  The Urinary Tract (a.k.a. “Renal System”) Excretion of toxins by the kidneys occurs via the urinary tract, which consists of the bladder, kidneys, ureters, and urethra. Kidney Anatomy of the Urinary Tract a) Aorta carries oxygenated blood to the kidneys through the renal arteries. Anatomy of the Urinary Tract a) Aorta carries oxygenated blood to the kidneys through the renal arteries. b) Renal Artery brings unfiltered and oxygenated blood to the kidneys Anatomy of the Urinary Tract a) Aorta carries oxygenated blood to the kidneys through the renal arteries. b) Renal Artery brings unfiltered and oxygenated blood to the kidneys c) Kidney - Wastes and excess water are filtered from the blood by the kidneys Anatomy of the Urinary Tract d) Ureter - Wastes and excess water are transported through ureters to the bladder. Anatomy of the Urinary Tract d) Ureter - Wastes and excess water are transported through ureters to the bladder. e) Bladder - As the bladder begins to fill with Urine, receptors in the brain are activated Anatomy of the Urinary Tract d) Ureter - Wastes and excess water are transported through ureters to the bladder. e) Bladder - As the bladder begins to fill with Urine, receptors in the brain are activated f) Urethra - Urine will exit the body through the urethra. Anatomy of the Urinary Tract g) Renal Vein - Once blood is filtered by the kidneys, it returns to the heart through the renal veins Anatomy of the Urinary Tract g) Renal Vein - Once blood is filtered by the kidneys, it returns to the heart through the renal veins h) Vena Cava - brings clean and deoxygenated blood to the heart Anatomy of the Kidneys Anatomy of the Kidneys A cross-section of the kidney reveals three layers: a) An outer layer of connective tissue known as the cortex encircles the kidney Anatomy of the Kidneys A cross-section of the kidney reveals three layers: a) An outer layer of connective tissue known as the cortex encircles the kidney b) An inner layer known as the medulla lies beneath the cortex Anatomy of the Kidneys A cross-section of the kidney reveals three layers: a) An outer layer of connective tissue known as the cortex encircles the kidney b) An inner layer known as the medulla lies beneath the cortex c) A hollow chamber known as the renal pelvis joins the kidney with the ureter  The Nephron Kidneys are composed of millions of slender tubules called nephrons. Nephrons span the cortex and medulla of each kidney, and act to remove waste products and other solutes from the blood. They also allow for the reabsorption of water and solutes back into the bloodstream, thereby maintaining homeostasis. Any solutes & water that are not reabsorbed are excreted in the form of urine. The Nephron  Bowman’s Capsule Distal Tubule Proximal Efferent Tubule Arterioles Afferent Collecting Arterioles Duct Glomerulus Loop of Henle Kidney Composition: Movement of Blood through Nephrons Small branches from the renal artery known as the afferent arterioles supply the nephrons with blood Kidney Composition: Movement of Blood through Nephrons Small branches from the renal artery known as the afferent arterioles supply the nephrons with blood The afferent arterioles branch into a group of capillaries known as the glomerulus. Kidney Composition: Movement of Blood through Nephrons Small branches from the renal artery known as the afferent arterioles supply the nephrons with blood The afferent arterioles branch into a group of capillaries known as the glomerulus. Blood leaves the glomerulus by way of the efferent arterioles. It then moves through the peritubular capillaries and eventually exits the kidney via the renal vein. Kidney Composition: Movement of Blood through Nephrons The glomerulus is surrounded by a funnel-like structure called the Bowman’s capsule Kidney Composition: Movement of Blood through Nephrons The glomerulus is surrounded by a funnel-like structure called the Bowman’s capsule The Bowman’s capsule, afferent arteriole, and efferent arteriole are located in the cortex of the kidney Kidney Composition: Movement of Blood through Nephrons The glomerulus is surrounded by a funnel-like structure called the Bowman’s capsule The Bowman’s capsule, afferent arteriole, and efferent arteriole are located in the cortex of the kidney Fluid to be processed into urine enters the Bowman’s capsule from the blood. The capsule tapers to a thin tubule, called the proximal tubule Kidney Composition: Movement of Blood through Nephrons Urine is carried from the proximal tubule to the loop of Henle, which descends into the medulla of the kidney Kidney Composition: Movement of Blood through Nephrons Urine is carried from the proximal tubule to the loop of Henle, which descends into the medulla of the kidney Urine moves through the distal tubule, the last segment of the nephron, into the collecting ducts. These ducts gather urine from many nephrons, which then merge in the pelvis of the kidney. Formation of Urine Urine formation is the result of three steps: 1) Filtration Accomplished by the movement of fluid from the blood into the Bowman’s capsule. 2) Reabsorption Involves the transfer of essential solutes and water from the nephron back into the blood. 3) Secretion Involves the transport of materials from the blood into the nephron 1) Filtration As blood moves through each nephron of the kidney, it must pass through the glomerulus into the Bowman’s capsule The glomerulus acts like a high-pressure filter, allowing only certain substances to enter the Bowman’s capsule and move on into the proximal tubule 1) Filtration Things that can pass through Things that cannot pass the glomerulus (components through the glomerulus of filtrate) (remain in bloodstream) The activity of the glomerulus thus explains why red blood cells are not found in the urine of a healthy person 1) Filtration Things that can pass through Things that cannot pass the glomerulus (components through the glomerulus of filtrate) (remain in bloodstream) Water Blood plasma proteins Salts Erythrocytes Glucose Platelets Amino acids Hydrogen ions Urea The activity of the glomerulus thus explains why red blood cells are not found in the urine of a healthy person  Urine gets its distinct smell from the urea that passes through the glomerulus. Urea is derived from excess protein. What’s that smell? Essentially, when you obtain more protein than your cells require, these proteins are broken down into amino acids in your liver. This results in the production of ammonia, a nitrogenous compound (NH4) that can become toxic if it builds up. In the liver, two molecules of ammonia are combined with a molecule of CO2 to form urea, which is eventually released into the bloodstream and excreted through the kidneys into your urine. 2) Reabsorption 2) Reabsorption Reabsorption of water, salt, glucose, potassium, amino acids, and urea begins in the proximal tubule. 2) Reabsorption Reabsorption of water, salt, glucose, potassium, amino acids, and urea begins in the proximal tubule. The majority of water reabsorption occurs in the descending limb of the Loop of Henle. The Loop of Henle extends down into the extremely salty medulla, allowing water to be absorbed via osmosis. 2) Reabsorption Reabsorption of water, salt, glucose, potassium, amino acids, and urea begins in the proximal tubule. The majority of water reabsorption occurs in the descending limb of the Loop of Henle. The Loop of Henle extends down into the extremely salty medulla, allowing water to be absorbed via osmosis. The ascending limb of the Loop of Henle is not permeable to water. Here, salt (NaCl) is reabsorbed through diffusion (in the lower portion) and active transport (in the upper portion). 2) Reabsorption Reabsorption of water, salt, glucose, potassium, amino acids, and urea begins in the proximal tubule. The majority of water reabsorption occurs in the descending limb of the Loop of Henle. The Loop of Henle extends down into the extremely salty medulla, allowing water to be absorbed via osmosis. The ascending limb of the Loop of Henle is not permeable to water. Here, salt (NaCl) is reabsorbed through diffusion (in the lower portion) and active transport (in the upper portion). In the distal convoluted tubule, additional water and salt can be reabsorbed if necessary. This requires the action of hormones. 2) Reabsorption Reabsorption of water, salt, glucose, potassium, amino acids, and urea begins in the proximal tubule. The majority of water reabsorption occurs in the descending limb of the Loop of Henle. The Loop of Henle extends down into the extremely salty medulla, allowing water to be absorbed via osmosis. The ascending limb of the Loop of Henle is not permeable to water. Here, salt (NaCl) is reabsorbed through diffusion (in the lower portion) and active transport (in the upper portion). In the distal tubule, additional water and salt can be reabsorbed if necessary. This requires the action of hormones. The collecting ducts in the kidney play a key role in the reabsorption of water, sodium, and urea and secrete acid and potassium. How Can We Influence This? Hormones Direct reabsorption of water is aided by a hormone known as antidiuretic hormone (ADH). ADH increases the permeability of the collecting ducts to H2O. Consequences of hypersecretion? Consequences of hyposecretion?  Reabsorption of sodium is aided by a hormone known as aldosterone. Aldosterone makes the distal tubules more permeable to NaCl. As a result, water is also reabsorbed to maintain the osmotic gradient. Consequences of hypersecretion? Consequences of hyposecretion? 3) Secretion Secretion is the movement of wastes from the blood into the proximal tubule, distal tubule, or collecting duct of a nephron. Ammonia, excess H+ ions, and minerals are examples of substances that are secreted. 3) Secretion pH is controlled by the secretion of excess hydrogen ions and restoration of bicarbonate ions in the blood. Kidney Dysfunction Chapter 12.2 Outcomes D3.1k identify the principal structures in the excretory system; i.e., kidneys, ureters, urinary bladder, urethra D3.2k identify the major and associated structures of the nephron, including the glomerulus, Bowman’s capsule, tubules, loop of Henle, collecting duct, afferent and efferent arterioles, and capillary net, and explain their function in maintaining plasma compositions (i.e., water, pH, ions) D3.3k describe the function of the kidney in excreting metabolic wastes and expelling them into the environment D3.4k identify the role of antidiuretic hormone (ADH) and aldosterone in water and sodium ion reabsorption, excretion and blood pressure regulation.  Kidney Dysfunction Proper functioning of the kidneys is essential for the body to maintain equilibrium. Many kidney disorders can be diagnosed by analyzing a urine sample. Diabetes Mellitus Diabetes mellitus is caused by inadequate secretion of insulin from islet cells in the pancreas. This affects the function of the kidneys, as insulin is required for cells to absorb glucose from the bloodstream… Without insulin, blood glucose levels remain higher than necessary, causing much of this glucose to be excreted in the urine. Because of the osmotic gradient high blood glucose levels creates, water is unable to be reabsorbed into the bloodstream from the nephron (disrupts passive transport of H2O). As a result, large amounts of water are lost, explaining why individuals with this form of Insulin injections are an effective diabetes are often thirsty. treatment for diabetes mellitus Diabetes Insipidus Diabetes insipidus results from a defect in a different hormone referred to as antidiuretic hormone (ADH), which regulates water reabsorption in the nephron. Without ADH, the nephron becomes less permeable to water, and less H2O is removed from the filtrate Extreme thirst is also a sign of As a result, individuals with diabetes diabetes insipidus also produce insipidus large volumes of urine (however, their urine does not contain high concentrations of glucose) Nephritis Nephritis is a general term used to describe an array of diseases characterized by inflammation of the nephrons. This is most often the result of some sort of urinary tract infection, with bacteria entering the body through the urethra. One type of nephritis affects the blood vessels of the glomerulus. Toxins produced by invading microbes destroy the blood vessels and alter the permeability of the nephron. This causes proteins and other large molecules to pass into the nephron rather than being filtered out. As a result, the osmotic gradient is altered, drawing water into the nephron. Individuals with this form of nephritis thus produce large quantities of urine with a high protein concentration. Kidney Stones Kidney stones are caused by the precipitation of mineral solutes from the blood. This typically occurs when your urine contains more calcium or uric acid than the fluid in your urine can dilute. Kidney stones may develop as a result of an unbalanced diet; too much protein, salt, or sugar in addition to inadequate amounts of water can lead to precipitation of these solutes. The sharp-sided stones can become lodged in the renal pelvis, or they may move down the ureter into the bladder and be excreted through the urine. Either way, kidney stones are extremely painful. High-energy shockwaves can be used to break the kidney stones into smaller fragments which can be easily passed. Kidney Dialysis For people whose kidneys cannot effectively process bodily wastes, a dialysis machine can help restore the proper solute balance. It does so by removing any additional wastes, salt and water from blood to prevent them from building up in the body...