Question

18. Explain the process of reabsorption using the following structures.

a. Tubular Lumen, Tubular cells, Tubular fluid, Peritubular fluid, Peritubular capillary

****PLEASE USE THESE TERMS

Answer 1

Tubular reabsorption is the process by which solutes and water are removed from the tubular fluid in the renal tubular lumen and transported to the peritubular capillary (blood vessel). In reabsorption the solutes and water move from the proximal convoluted tubule to the interstitial space which contain  the peritubular fluid and then into peri-tubular capillaries.

A large amount of reabsorption occurs in proximal convoluted tubule, In the PCT 65% of water, 100% of glucose, 100% amino acids, 65% of potassium, 65% chloride and 67% of sodium is reabsorbed. Tubular cells of the proximal tubule have an elaborate brush border, the brush border and the extensive length of the proximal tubule dramatically increases the surface area for reabsorption enabling it to nearly absorb 70% of the filterate.

In the PCT there are a large amount of solutes being transported out, this means that their concentrations in the tubule are decreasing and their concentrations in the interstitium are increasing. The difference in concentration gradient results in the water moving in the same direction as the solutes into the intertitium via osmosis.