PHGY 210 Lecture Notes - Lecture 4: Tubular Fluid, Proximal Tubule, Extracellular Fluid
27 Nov 2015
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Document Summary
Renal physiology lecture 4: regulation of water balance. Osmolarity: total solute concentration of a solution; measure of water concentration in that the higher the solution osmolarity, the lower the water concentration. Hypoosmotic: having total solute concentration less than of normal extracellular fluid (300 mosm) Hyperosmotic: having total solute concentration greater than that of normal extracellular fluid. Isoosmotic: having total solute concentration equal to that of normal extracellular fluid. Water is freely filtered but ~99% is reabsorbed. The majority of water reabsorption (~2/3) occurs in the proximal tubule. But the major hormonal control of reabsorption occurs in the cd. This dynamic regulation takes place in cd and there are two critical components: high osmolarity of the medullary interstitium, permeability of cd to water (regulated by vasopressin) The kidney has the ability to concentrate urine up to 1400 mosm/l. Urinary concentration takes place as tubular fluid flows through the medullary collecting ducts. Urinary concentration depends on the hyperosmolarity of the interstitial fluid.
