NPB 101 Lecture Notes - Lecture 27: Aquaporin, Aldosterone, Natriuretic Peptide
11 Nov 2017
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Document Summary
Tubular reabsorption is the selective movement of filtered substances from the tubular lumen into the peritubular capillaries. Key properties of tubular epithelium: throughout its entire length, the tubules is one cell-layer thick, tubular epithelial cells have a luminal membrane and a basolateral membrane. Key properties of capillary endothelium: throughout its entire length, the tubule is one very thin cell layer thick, no tight junctions between endothelial cells -> little barrier for water and solutes, fenestrated capillaries are even more permeable. Two types of tubular reabsorption: passive reabsorption: movement down an osmotic or electrochemical gradient, active reabsorption: requires energy, includes na+, glucose, amino acid and other electrolytes. Na+ reabsorption is unique, complex and very important. 99. 5% of filtered na is reabsorbed: 67% proximal tubule, 25% loop of henle, 8% distal and collecting tubules. In the distal tubule na+ reabsorption is subject to hormonal control, being important in the regulation of ecf volume. The active step in na+ reabsorption involves the energy-dependent.
