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[Note: All Powerpoint Slides Are on the UVM Blackboard] ANPS 020 Fiekers 05-01-13 [Note: All PowerPoint slides are on the UVM Blackboard] [ON SCREEN] Summary of renal function SUMMARY OF RENAL FUNCTION Step 1: Filtrate produced at the renal corpuscle has the same osmotic concentration as plasma (300 mOsm/L) but without the plasma proteins. Step 2: Removal of ions and organic substrates produces a continuous osmotic flow of water from the tubular fluid. Volume of filtrate reduces filtrate volume but keeps the solutions inside and outside the tubule isotonic. Step 3: in the PCT and descending limb of the nephron loop, water moves into the surrounding peritubular fluid leaving a small volume of highly concentrated tubular fluid. This reduction occurs by obligatory water reabsorption. Step 4: the tick ascending limb is impermeable to water and solutes. The cells transport Na+ and Cl- out of the tubule, lowering the osmotic concentration of the tubular fluid. Because just Na+ and Cl- are removed, urea accounts for a higher proportion of the total osmotic concentration at the end of the loop. Step 5: the final adjustments in the composition of the tubular fluid occur in the DCT and the collecting system. This area is where final composition occurs, regulating acid base balance. Step 6: DCT and collecting ducts: final adjustments in the volume and osmotic concentration of the tubular fluid are made by controlling the water permeability of the distal portions of the DCT and the collecting system. The level of exposure to ADH determines final urine concentration. Step 7: The vasa recta absorbs solutes and water reabsorbed by the nephron loop and the collecting ducts. Removing these solutes and water into the main circulatory system, the vasa recta maintains the concentration gradient of the medulla. Professor comments PROFESSOR COMMENTS Think of the kidney’s actions on second-to-second basis, all the principles involved in forming urine. Pretty amazing. This is a summary of what we talked about in the preceding class. Human Anatomy& Physiology - 1 ANPS 020 Fiekers 05-01-13 Professor reads about a new drug on the market that was announced yesterday: “Invocal is a first new class of drugs for Type 2 Diabetes that inhibits uptake of glucose in the nephron tubule by blocking this particular transporter It is referred to as SGLT2 inhibitor but they don’t name the transport.” o If something is left in the filtrate, water remains behind for osmotic balance so we pee out more water. o The problem with this is dehydration. If you void more water, users must drink more water. Glucose composition is changed by the drug but you have dehydration. o It is important to have the vocabulary so you understand what pharmaceutical companies are doing. o Read the titles of library articles: 75-80% of titles tell you what drug companies are doing and the fact is they have no idea what they are doing. Scientific jargon is not important; the transport is important. o 3-4 days ago CBS Nightly News reported a huge breakthrough that gives hope for Juvenile Diabetes sufferers. Stem cells are important because these key cells can replace cells in organs. They found stem cells in the pancreas that became beta cells when the autoimmune response is normally to destroy them. If you can increase production and make people less susceptible to attack, the cells increase insulin and you can help people who must use insulin daily. This is a huge hope to come about in the last 5-8 years. If you know your vocabulary you’ll understand how big this discovery is. Responses to questions on the exam PROFESSOR RESPONSE TO QUESTIONS ON THE EXAM Worksheets require thinking but they are reiterations of things we talked about in class. Human Anatomy& Physiology - 2 ANPS 020 Fiekers 05-01-13 The exam is multiple choice, fill in the blanks. If you can come up with the word, you understand the material. If you have questions on this I can clarify by email. Go over filtration: What happens to the filtration rate when the glomerulus is constricted? Decreased blood flow which affects amount of filtrates we produce. Must actively change filtrate rate also. Think about changing the flow: a group of vessels go in and out and if you dilate you have more flow and higher pressure and increased filtration rate) depending on the blood. If you increase blood pressure, you have increased blood flow. These are delicate capillaries. It’s not a hormonal intervention; they are responding to a reflex constriction that is responding to higher pressure. Think about the anatomical and physiological differences. You concentrate urine in the presence of ADH. The proximate tubule works the same except for its ability to produce hypertonic gradient. This is critical because it regulates the amount of water we lose. It lets us be more mobile otherwise we’d be tied to a source of water. Know the parts of the glomerulus filtration membrane: What structures must substances go through? Jeopardy game on the urinary system JEOPARDY GAME ON THE URINARY SYSTEM (CHAPTER 26) Q: Why is the presence of microvilli important to the epithelial tissue of the PCT? A: because reabsorption is occurring. Q: Damage to which part of the nephron interferes with hormonal control of blood pressure? A: Juxtaglomerular apparatus because it contains the juxtaglomerular cells which secrete renin (hormonal control of blood pressure). Q: What is role of the vasa recta in the urinary system? A: Returns water and solutions to the general circulation. Q: What effect does an increased amount of aldosterone have on K+ concentration of urine? A: K+ increases o (aldosterone secretion increases sodium reabsorption; where does aldosterone come from, where is it working?) Human Anatomy& Physiology - 3 ANPS 020 Fiekers 05-01-13 Q: What nephron structures are involved in filtration? A: Glomerular capillars, lamina densa, and filtration slits of the podocytes. o Filtration occurs in the glomerulus. Q: Why don’t plasma proteins pass into the capsular space under normal circumstances? A: Glomerular capillary pores are too small. Q: How does the diameter of the lumen of the loop of Henle change along its length? A: The lumen doesn’t change but the cells are thicker. o The lumen is the same diameter along its length. Q: Why does a decrease in Na+ in the distal convoluted tubule lead to an increase in blood pressure? A: Because it increases renin production. Q: How are cortical and juxtamedullary nephrons structurally different? A: Juxtamedullary nephrons have longer loops of Henle. Q: An obstruction of a ureter by a kidney stone limits the flow of urine between which two points? A: Renal pelvis and urinary bladder. o An obstruction prevents anything moving below. Q: The ability to control the micturition reflex depends on the ability to control which muscle? A: External urinary sphincter. o micturition reflex = body’s voiding of urine Q: Why does osmotic concentration decrease in the thick ascending limb of the loop of Henle? A: Na+, K and Cl- are actively transported out of the tubular fluid. Q: What event occurs when the plasma concentration of a substance exceeds its tubular maximum? A: Excess is excreted in urine. Jeopardy game on Blackboard PROFESSOR WILL POST THE JEOPARDY GAME ON THE UVM BLACKBOARD. [CLASS ENDS. END OF SEMESTER.] Human Anatomy& Physiology - 4.
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