Question

Renal System

Describe (include the hormonal control) how water is being reabsorbed from the filtrate into the peritubular circulation.  

Answer 1

TUBULAR REABSORPTION is the process by which water is transported from renal tubules back to blood in peritubular capillaries. Large quantity of water and other substances are reabsorbed by tubular epithelial cells. The reabsorbed substances move into the interstitial fluid of renal medulla and from there into the boood in peritubular capillaries.

Water is reabsorbed by passive reabsorption. In passive reabsorption molecules move along the electrochemical gradient.

Water is reabsorbed from proximal convoluted tubule (maximun) and distal convoluted tubule.

–Tubular reabsorption is regulated by three factors:

1. Glomerulotubular balance.

2. Hormonal factors.

3. Nervous factors.

HORMONAL FACTORS THAT REGULATE TUBULAR REABSORPTION OF WATER :

ADH - It is a hypothalamic hormone and is stored and released by posterior pituitary. When osmoreceptors sense changes in blood osmotic pressure they stimulate the posterior pituitary to release ADH. ADH increases water reabsorption in distal convoluted tubule and collecting duct. ADH binds to the receptors on cells in collecting duct and DCT and promotes reabsorption of water back into circulation.