nephron The excretory unit of the vertebrate kidney (see illustration). Many constituents of the blood are filtered from the glomerulus into the Bowman's capsule at one end of the nephron. The glomerular filtrate passes along the length of the nephron and some of its water, plus some salts, glucose, and amino acids, are reabsorbed into the surrounding blood capillaries (see proximal convoluted tubule; loop of Henle; distal convoluted tubule). More water is reabsorbed in the collecting duct, and the resulting concentrated solution of nitrogen-containing waste matter (urea in most mammals) plus inorganic salts drains from the collecting ducts of the nephrons and is discharged as urine into the ureter.

nephron Functional unit of the mammalian kidney. There are c.1 million nephrons in a human kidney. Each consists of a cluster of tiny blood capillaries, cupped in a structure with an attached, narrow tubule. Blood enters the kidney under pressure, and water and wastes are forced into the tubule. Some water and essential molecules are reabsorbed into the bloodstream; the remaining filtrate, urine, is passed to the bladder.

nephron (nef-ron) n. the active unit of excretion in the kidney (see illustration). Blood is filtered through the glomerulus into the Bowman's capsule so that water, nitrogenous waste, and many other substances pass into the renal tubule. Here most of the substances are reabsorbed back into the blood, the remaining fluid (urine) passing into the collecting duct, which drains into the ureter.

nephron One of the units in the vertebrate kidney that extracts metabolic wastes which are discharged as urine. The Bowman's capsule, at one end of the nephron, receives many blood constituents, and the loop of Henlé extracts water and some salts. See COUNTER-CURRENT EXCHANGE.