Excretory System.pdf

8/27/24, 6:09 PM Platform | Study Fetch The Excretory System (00:00 - 00:13) Introduction to the topic of the excretory system (00:13 - 00:23) The excretory system filters out excess and waste materials from the body...

8/27/24, 6:09 PM Platform | Study Fetch The Excretory System (00:00 - 00:13) Introduction to the topic of the excretory system (00:13 - 00:23) The excretory system filters out excess and waste materials from the body It ensures the body has the necessary cells to perform life functions (00:23 - 00:40)Lesson Overview: Discuss the key players of the kidney and the Nephron Explore the excretory pathways (00:40 - 00:58)Anatomy of the Kidney: The cortex is where blood enters the kidney from the body The medulla is the middle part between the cortex and the pelvis The pelvis is where the final product, urine, collects for excretion from the body (00:58 - 01:11)The Nephron: The Nephron is the individual unit of the kidney It is responsible for filtration, reabsorption, secretion, and excretion (01:11 - 01:27)Kidney Processes: Mnemonic: "Fat rats C" - Filtration, Reabsorption, Secretion, and Excretion (01:27 - 01:40)Blood Flow in the Nephron: Blood flow starts at the afferent arteriole, then flows past Bowman's capsule and the glomeruli It then passes through the efferent arteriole and the vasa recta surrounding the rest of the Nephron (01:40 - 02:05)Excretory Pathway: 1. Filtration: Blood flows from the renal artery into the afferent arteriole It then enters the glomerulus, exerting pressure into Bowman's capsule (Bowman's space) Water and small solutes are able to flow from the blood into Bowman's capsule (02:05 - 02:32)2. Filtration (continued): There is a size-limiting barrier formed by the glomerular capillaries and Bowman's capsule This barrier is made up of the capillaries, the basement membrane, and the podocytes with their foot processes This mesh-like structure keeps proteins from flowing into the urine (02:32 - 02:55)3. Reabsorption and Secretion: The fluid in Bowman's capsule then flows through the Nephron Useful substances are reabsorbed back into the bloodstream Waste products are secreted into the urine for excretion (02:55 - 03:19)4. Excretion: The final urine product is collected in the renal pelvis and then flows out of the body through the ureters (03:19 - 03:33)Key Takeaways: The excretory system filters out excess and waste materials from the body The kidney and the Nephron are the key players in this process https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc1f069b6d6b89c5eb2/document?go=note 1/7 8/27/24, 6:09 PM Platform | Study Fetch The Nephron is responsible for filtration, reabsorption, secretion, and excretion The excretory pathway involves a complex series of steps, including filtration, reabsorption, and secretion The Nephron and Filtration in the Kidney (00:03:33 - 00:03:45) Small dissolved ions, like sugar, glucose, and water, can pass through the mesh-like filter (glomerular filtration barrier) into Bowman's capsule. (00:03:45 - 00:04:02) The amount of fluid that moves into Bowman's capsule is determined by various factors, primarily the pressure in the glomerular capillaries, which pushes water and solutes through the filtration barrier. (00:04:02 - 00:04:16) After the filtrate enters Bowman's capsule, it then flows into the efferent arteriole. (00:04:16 - 00:04:35) The body can increase the pressure in Bowman's capsule by constricting the efferent arteriole. This causes more blood and pressure to be pushed into Bowman's capsule, increasing the filtration rate. (00:04:35 - 00:04:45) The peritubular capillaries that surround the nephron tubules (vasa recta) facilitate the exchange of water and salts with the further parts of the nephron. (00:04:45 - 00:04:57) The mnemonic "A becomes a four E in the alphabet" can help remember that the efferent arteriole (E) comes after the afferent arteriole (A) in the kidney. (00:04:57 - 00:05:13) The efferent arteriole is the exit of the glomerulus, and this can be another way to remember the mnemonic. (00:05:13 - 00:05:33) Reabsorption occurs in the loop of Henle, where water and solutes are removed from the filtrate and returned to the blood vessels. The amount of reabsorption is modulated based on factors like hydration status and salt intake. (00:05:33 - 00:05:49) The ascending limb of the loop of Henle has high permeability to solutes but low permeability to water, while the descending limb has high permeability to water but low permeability to solutes. (00:05:49 - 00:06:09) The proximal tubule is where a lot of nutrient reabsorption, like glucose and bicarbonate, occurs. (00:06:09 - 00:06:22) From the proximal tubule, the filtrate then enters the loop of Henle. The Loop of Henle and Reabsorption (00:06:22 - 00:06:32) The loop of Henle is an important structure for the reabsorption of water and solutes from the filtrate. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc1f069b6d6b89c5eb2/document?go=note 2/7 8/27/24, 6:09 PM Platform | Study Fetch Key Points: Small dissolved ions can pass through the glomerular filtration barrier into Bowman's capsule Pressure in the glomerular capillaries drives fluid filtration into Bowman's capsule The efferent arteriole can be constricted to increase pressure and filtration in Bowman's capsule Peritubular capillaries (vasa recta) facilitate exchange of water and salts with the nephron Mnemonic: "A becomes a four E in the alphabet" to remember afferent vs. efferent arterioles Reabsorption occurs in the loop of Henle, with differential permeability to water and solutes Proximal tubule is where nutrient reabsorption, like glucose and bicarbonate, takes place The Kidney and Urine Formation (00:06:32 - 00:06:43) Water is reabsorbed in the descending loop of Henle, which is permeable to water but not to salt This causes the fluid traveling through the loop of Henle to become more and more concentrated as it descends (00:06:43 - 00:07:00) As the fluid travels back up the ascending loop of Henle and the thick loop of Henle, salts are reabsorbed This causes the fluid in the loop of Henle to become more dilute as it ascends (00:07:00 - 00:07:11) The loop of Henle concentrates the fluid by pulling up water, and then dilutes it by pulling out salt This process of concentrating and diluting allows for the resorption of both water and salt as the fluid passes through the loop of Henle (00:07:11 - 00:07:26) Secretion occurs at the proximal convoluted tubule and the collecting duct Secretion is the transfer of solutions from the blood and vasculature into the nephron and tubule filtrate (00:07:26 - 00:07:37) Secretion can be used to regulate the body's pH, such as by secreting more H+ ions to acidify the urine when the body is too acidic (00:07:37 - 00:07:50) Secretion can also be used to control potassium balance by secreting potassium out into the urine, which occurs in the collecting duct (00:07:50 - 00:08:03) Excretion is the removal of waste, such as urea and other byproducts of metabolism, which are removed from the body through the urine (00:08:03 - 00:08:14) The ureter connects the kidney to the urinary bladder, allowing the urine to be stored and eventually expelled from the body through the urethra (00:08:14 - 00:08:29) The formation of urine involves the following steps: Filtration in the glomerulus Reabsorption and secretion in the nephron Excretion of waste products https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc1f069b6d6b89c5eb2/document?go=note 3/7 8/27/24, 6:09 PM Platform | Study Fetch (00:08:29 - 00:08:43) The urinary system consists of the kidneys, ureters, bladder, and urethra, which work together to filter, store, and expel urine from the body (00:08:43 - 00:08:55) The renal artery carries blood to the glomerulus, where filtration occurs based on the pressure in the glomerulus (00:08:55 - 00:09:08) The filtered fluid then travels through the nephron, where reabsorption and secretion occur, before being expelled as urine through the urinary system The Nephron: Filtration and Reabsorption (00:09:08 - 00:11:55) Filtration in Bowman's Capsule Water and small molecules are forced into Bowman's capsule In a healthy kidney, the filtration barrier (endothelial cells, basement membrane, podocytes) prevents cells and proteins from entering Bowman's capsule A small amount of protein may still leak through the filtration barrier Proximal Convoluted Tubule This is the main site of reabsorption in the body Glucose, bicarbonate, and other substances are reabsorbed here Descending Loop of Henle Primarily reabsorbs water due to its permeability to water Ascending Loop of Henle Reabsorbs salts, but is impermeable to water Distal Convoluted Tubule Site of some salt reabsorption and other minor functions Collecting Duct Main site for reabsorption of salts and excretion of acid and potassium Final step in urine formation Urine Formation and Excretion https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc1f069b6d6b89c5eb2/document?go=note 4/7 8/27/24, 6:09 PM Platform | Study Fetch Urine flows from the collecting duct to the renal pelvis, ureter, bladder, and finally out through the urethra Key Hormones Parathyroid Hormone (PTH): Mobilizes calcium from bone Increases calcium absorption from the gut Calcitonin: Decreases blood calcium levels Aldosterone: Produced by the adrenal cortex Acts on the collecting duct to regulate sodium and potassium balance (00:09:08 - 00:09:22) Water is forced into Bowman's capsule In a healthy kidney, the filtration barrier (endothelial cells, basement membrane, podocytes) prevents cells and proteins from entering Bowman's capsule (00:09:22 - 00:09:32) The filtration barrier allows a small amount of protein to leak through (00:09:32 - 00:09:44) The proximal convoluted tubule is the main site of reabsorption in the body Glucose, bicarbonate, and other substances are reabsorbed here (00:09:44 - 00:09:56) The descending loop of Henle primarily reabsorbs water due to its permeability to water (00:09:56 - 00:10:08) The ascending loop of Henle reabsorbs salts, but is impermeable to water (00:10:08 - 00:10:20) The distal convoluted tubule is a site of some salt reabsorption and other minor functions (00:10:20 - 00:10:32) The collecting duct is the main site for reabsorption of salts and excretion of acid and potassium This is the final step in urine formation (00:10:32 - 00:10:46) Urine flows from the collecting duct to the renal pelvis, ureter, bladder, and finally out through the urethra (00:10:46 - 00:11:00) Parathyroid hormone (PTH) mobilizes calcium from bone and increases calcium absorption from the gut Calcitonin decreases blood calcium levels (00:11:00 - 00:11:11) Aldosterone is produced by the adrenal cortex and acts on the collecting duct to regulate sodium and potassium balance (00:11:11 - 00:11:25) Parathyroid hormone (PTH) and its role in calcium balance are discussed in more detail in the bone module https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc1f069b6d6b89c5eb2/document?go=note 5/7 8/27/24, 6:09 PM Platform | Study Fetch (00:11:25 - 00:11:37) Aldosterone is a key hormone that regulates the collecting duct (00:11:37 - 00:11:55) Aldosterone targets specific cells in the collecting duct, and its function can be altered by certain drugs to help manage diseases The Kidney and Hormone Regulation (00:11:55 - 00:12:09) Aldosterone is secreted by the adrenal cortex in response to the renin-angiotensin-aldosterone system (RAAS). The RAAS system helps regulate blood volume and pressure. (00:12:09 - 00:12:22) In low volume situations, aldosterone increases the absorption of salt and water to increase intravascular volume. (00:12:22 - 00:12:32) Anti-diuretic hormone (ADH), also called vasopressin, is secreted by the posterior pituitary. (00:12:32 - 00:12:45) The hypothalamus senses the osmolarity (salt concentration) of the blood and regulates ADH release accordingly. ADH acts to prevent excessive water loss by increasing water reabsorption in the kidneys. (00:12:45 - 00:13:00) If blood becomes too salty or has too little salt, the hypothalamus adjusts ADH release to maintain proper osmolarity. (00:13:00 - 00:13:11) ADH increases water reabsorption in the kidneys, leading to more concentrated urine and less urine production. (00:13:11 - 00:13:22) ADH is an anti-diuretic hormone, opposing diuresis (increased urine production). (00:13:22 - 00:13:39) ADH regulates water balance by adjusting the osmolarity of the blood, whereas aldosterone regulates blood volume and pressure. Aldosterone increases both salt and water reabsorption, but does not directly affect blood osmolarity. (00:13:39 - 00:13:55) Natriuretic peptide is released from the heart in response to cardiac stretch, causing increased water and salt excretion to reduce blood volume. This opposes the effects of the aldosterone system. (00:13:55 - 00:14:21) Natriuretic peptide is released when there is too much volume/stretch in the cardiovascular system, causing increased water and salt excretion. This helps counteract the volume-increasing effects of the aldosterone system. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc1f069b6d6b89c5eb2/document?go=note 6/7 8/27/24, 6:09 PM Platform | Study Fetch (00:14:21 - 00:14:33) The various hormone systems work together to maintain proper blood volume, pressure, and osmolarity to keep the body healthy. (00:14:33 - 00:14:47) Understanding these key hormone systems that regulate kidney function and fluid balance is important for comprehending how the body maintains homeostasis. (00:14:47 - 00:14:57) Congratulations on mastering the excretory system! Keep up the great work, and you'll do amazing on the upcoming test. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cc1f069b6d6b89c5eb2/document?go=note 7/7