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Lecture 32
Renal Filtration-Reabsorption
Term | Definition |
---|---|
Renal Functions | Filter waste from blood. Maintain blood volume. Maintain blood osmolarity. Uses filtration,Reabsorption,secretion |
Nephron | Force unit for kidneys. Has vascular system and tubular system. All but cells and proteins in the blood can be filtered. Most reabsorbed remainder=urine. |
Vascular System | 2 capillary systems:1 for filtering,1 for reabsorption. Afferent arteriole leads to glomerulus (filtration) leads to efferent arteriole leads to peritubular capillaries (reabsrption) leads to venules |
Tubular System | s-shaped. Bowman's capsule (receives filtrate) leads to proximal tubule leads to loop of henie leads to distal tubule leads to collecting duct leads to ureter. Variable reabsorption. Hormonal control of volume and osmolarity. |
Glomerular Filtration | From glomerulus into bowman's capsule. glomerulur capillaries have very wide pores. Only cells and proteins not filtered. |
Inulin | Fructose polymer. Filtered, not reabsorbed or secreted.. used to measure glomurular filtration rate (GFR). Inject in blood-measure in urine-proportional to amount of filtrate. GFR-125mL/min, 1/40 of total blood volume. |
Hydrostatic/Osmotic Pressures | H:BP force filtrate into Bowman's capsule. OP: so much fluid is filtered,remaining proteins have higher than normal osmotic pressure. Net: lots of filtration. |
Control of GFR | Afferent arteriole radius controls entry to glomerulus. Aff. art. dialation inc. GFR. Aff art constriction dec. GFR. Symp n. constrict aff art. dec GFR. |
Tubular Reabsorption | Must recover most filtrate. 125 filtered 124mL/min reab leads to 1 mL urine, 1.44L/day. 125 filtered, 173mL/min read leads to 2 mL/day urine, 2.88L/day. Excess urine loss in diabteres leads to dec BP leads to shock leads to death |
Transport Maximum | Diff carriers for diff molecules. TM is limit of transport due to limited # of carriers |
Glucosuria | 3x more carrier capacity than normal filtered blood. If G in urine, blood must have at least 3x more G than normal. |
Sodium Reabsoption | controls reabsorption of many other molecules.Na+ pump only on basolateral side of tubular cells. Pump NA+ out,create gradient for Na+ entry into cells. ATP needed for energy. Tight junctions prevent flow in spaces btw cells. caffeine dec Na+ reabsorption |
Cotransport | Carriers for Na+ and cotrans molecule. glucose,amino acids,bicarbonate,Cl- are cotrans w/Na+ during reab.Energy use is NA+ movement down gradient into cells.H2O follows osmotically at proximal tubule.Variable H2O reab.at distal tubule and collection duct. |
Glucose Reabsorption | Binds to carrier w/ Na+ on lumenal side to enter tubule cell. Separate non Na+ glucose carrier moves into interstitial space. |
Proximal Tubule Water Reabsorption | 60-70% of water reab in PT. 180L/day filtered ~ 1L of urine variable. 500 mL of urine min. per day to remove toxins. Osmotic reabsorption of water follows solute,especially Na+ |