ANATOMY

Detailed explanation-1: -A: The ascending limb of the loop of Henle functions to dilute the filtrate by removing solutes. The thin segment of the ascending limb is not permeable to water, but it is permeable to solutes.

Detailed explanation-2: -The thick ascending limb of Henle’s loop actively reabsorbs sodium chloride (NaCl) but is impermeable to water. Therefore this segment raises the osmolality of the interstitial fluid, thus generating medullary interstitial hypertonicity and a lumen-to-interstitium osmotic gradient.

Detailed explanation-3: -In summary, the loop of Henle is surrounded by tissue fluid which has a high concentration of ions in it. This causes water to move out of the descending limb by osmosis. This produces a more concentrated filtrate because of this, ions move out of the loop in the thin ascending limb.

Detailed explanation-4: -In the third segment of the loop, the thick ascending limb, the tubule wall can, if necessary, effect further removal of salt, even against the concentration gradient, in an active-transport process requiring the expenditure of energy.

Detailed explanation-5: -Water present in the filtrate in the papillary duct flows through aquaporin channels out of the duct, moving passively down its concentration gradient. This process reabsorbs water and creates a concentrated urine for excretion.