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Unformatted text preview: Lecture 12: Water and Salt Balance of the Kidney General o Compartmental distribution of salt and body water o relationship between ICFV, ECFosm, ECFNa ICFV Intraceullar Fluid Volume ECFosm Extracellular fluid osmolality/osmolarity ECFNa Extracellular Fluid Sodium Concentration o Disturbances and regulation of salt and water intake Physiology of Sodium o avg adult eats ~100-120 millimoles of sodium each day about 1/10 gets excreted as feces most of that gets absorbed its distributed b/n the intra and extracellular fluid o more mmoles in ECF than ICF there is a balance equilibrium-- established between ECF and ICF and the amount thats lost (ex. in perspiration) o kidneys are charged with filtering 25,500 millimoles of Na (25,500 is the filtered load) filtered load = glomerular filtration rate (X) Na concentration in plasma 99.6% of which gets reabsorbed on a daily basis, kidneys excrete 3-4/10s of a filtered load (about 100 millimoles) How renal tubular system processes Na o in early proximal tubule: 100% of filtered load for Na is present o going downstream into beginning loop of henle : only 33% still remains in tubule o thus, about 67% of filtered load for Na gets reabsorbed in proximal tubule in the early proximal tubule o only 8% of filtered load remaining at the end of thick ascending limb o thus, only 25% has been reabsorbed somewhere in loop of Henlemost of filtered Na that escapes proximal tubule gets reabsorbed in thick ascending limb o between cortical and medullary collecting tubule, there is about 3% of the Na remaining most of that gets reabsorbed in the inner portion of medullary collecting duct.. leaving .4% of filtered load remaining to be excreted as urine o going back upstream only 5% of filtered load has been reabsorbed collectively by distal convoluted tubule, connecting tubule, initial collecting tubule, and cortical collecting tubule o volume of urine excreted and volume of Na excreted in urine is regulated Slide 1 Slide 2 Slide 3 Mechanisms for the segmental renal tubular reabsorption of NaCl o complexity of the reabsorbing mechanisms decrease from proximal to distal tubules o if were to express the work that the kidney does each day as reabsorption of sodium filtered load, most of oxygen that kidney consumes is for the reabsorption of Sodium occurs in the epithelial cells of the early proximal tubule o Early Proximal Tubule: left = tubular lumen...
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- Fall '08