MEDICAL PHYSIOLOGY

Detailed explanation-1: -An osmotic gradient is established and maintained by selective permeability in the loops of Henle (countercurrent multipliers) and passive diffusion in the vasa recta (countercurrent exchangers).

Detailed explanation-2: -The vasa recta of the kidney, (vasa recta renis) are the straight arterioles, and the straight venules of the kidney, – a series of blood vessels in the blood supply of the kidney that enter the medulla as the straight arterioles, and leave the medulla to ascend to the cortex as the straight venules.

Detailed explanation-3: -The countercurrent exchange of water and solutes between the ascending vasa recta (AVR) and descending vasa recta (DVR) and the interstitium preserves the osmotic gradient by preventing the rapid transfer of solutes away from the medulla (Pallone et al.

Detailed explanation-4: -The vasa recta capillaries are long, hairpin-shaped blood vessels that run parallel to the loops of Henle. The hairpin turns slow the rate of blood flow, which helps maintain the osmotic gradient required for water reabsorption.