loop of Henle The hairpin-shaped section of a kidney tubule situated between the proximal and distal tubules in the nephron. The loop of Henle extends from the cortex into the medulla; it consists of a thin descending limb, which is permeable to water, and a thick ascending limb, which is impermeable to water. Complex movements of ions and water across the walls of the loop enable it to function as a countercurrent multiplier, resulting in the production of concentrated urine in the collecting duct. It is named after German anatomist F. G. J. Henle (1809–85).

loop of Henlé See COUNTER-CURRENT EXCHANGE; NEPHRON.