Question

discuss the funtional regions of the nephron

Answer 1

Answer

1) Renal corpuscle

• Glomerulus : A tuft of fenetrated capillaries that allow filtration of the blood. Many small soluted including nitrogenous wastes, glucose, amino acids, electrolytes are filtered across the filtration membrane.
  
  
• Bowman's capsule : It contributes to form filtration membrane. Podocytes in visceral layer of the capsule contals foot processes that forms filtration slits. It prevents entry of large substances such as proteins and blood cells.  

2) Proximal convoluted tubule

• Nearly 2/3rd of water and NaCl from the filtrate is reabsorbed here.
• All the nutrients such as glucose amino acids are also reaborbed here.
• This process is facilitates by SGLT on apical membrane and GLUT transporters on the basolateral membrane of the epithelial cell of tubule.
• The basolateral membrane also contains sodium potassium pump to maintain intracellular sodium levels.
• Some harmful substances such as creatinine, drugs, reic acid are secreted into the tubule lumen.

3) Loop of Henle

• It forms a countercurrent multiplier to increase water reabsorption.

Descending limb : It is permeable to water and impermeable to solutes. Water is reabsorbed here.

Ascending limb : It is permeable to solutes and impermeable to water. NaCl is reabsorbed into the interstitial fluid.  

4) Distal convoluted tubule

• Active reabsorption of NaCl takes place here facilitated by the hormone aldosterone.
• Sodium reabsorption forms a concentration gradient that facilitates water reabsorption.
• Calcium is also reabsorbed in this tubule. PTH hormone increases the rate of calcium reabsorption.
• Secretion of H+, K+ and urea into the tubule.

5) Collecting duct

• It is the terminal region of the nephron.
• The cells of collecting duct are impermeable to water.
• When ADH hormone installs aquaporin water channels on the membrane of these cells, they become permeable to water.
• Water reabsorption occurs here in order to produce concentrated urine.