Question

Describe the 3 phases of urine formation in the kidney, highlighting specific transport mechanisms for both solutes and solvent, and the changes to the extracellular fluid compartment at each phase.

Answer 1

Mainly 3 phases are

1.filtration

2.resabsorption

3.secretion

All the 3 stages lead to formation of urine

Proximal convoluted tublule :glucose, amino acids ,phosphates ,HCO3, citrate are absorbed

Thick ascending loop of Henley:sodium and potasium absorbed and k+ lions secreted to lumen

DCT: sodium and chlorine absorbed by sodium and chlorine symport,calcium and magnesium are also absorbed

Cortical collecting duct -p cells :aldosterone acts on mineralo corticoid receptor and act on enac to absorb sodium and romk to secret potasium in to lumen .

Cortical collecting duct -alpha inter related cells : leads to secretion of H+ ions into the urine leads to reduce acidity in the blood .

Medulary collecting duct :anti diuretic harmone acts on the v2 receptor and leads tho absorption of water from the lumen through aquqporin 2