Kidney Function

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Kidney Function

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Lecture Note
University of Southern California
Bisc 307l - General Physiology
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BISC 307L 1st Edition Lecture 36 Current Lecture  Overview of Kidney Function o o 4 jobs  1. Filtration  leakage of fluid out of the capillaries into the glomerular tubule  like plasma minus the proteins  2. Reabsorption  from glomerular tubule back into the capillary  most of the salt  most of the water  glucose, amino acids  general process  3. Secretion  from blood into the lumen of the tubule  more of a selective process  concentration can change due to this  . Excretion  what comes out of the end of the collecting duct into the renal pelvis unaltered and is excreted In loop of henle only reabsorption occurs not secretion  180 L/day are filtered out of the plasma into bowmans capsule – all of your plasma is filtered 60 times a day so most of it has to be recovered  over 99% of the fluid that is being filtered is reabsorbed  300mOsM is the same as plasma  over 70% of the fluid is reabsorbed by the end of the proximal tubule by active transport of solutes and water follows by osmosis  because of the way the fluid is reabsorbed (transport of mostly salt) the osmolarity should stay the same and it does  by the end of the loop of henle the osmolarity is 100mOsM because so much salt was reabsorbed that the osmolarity went down- this is the only part of the nephron that can produce a hypoosmotic system- because sometimes you need to get rid of excess water  the osmolarity at the collecting duct varies due to reabsorption of water (can be as high as 1200)  Renal Corpuscle o o In order to understand look at the poking finger analogy o The outer wall is pretty non porous but the inner wall is very porous o Podocytes form filtration slits in the inner wall o 3 barriers that the fluid goes through  1.pores in the endothelium

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