<Tr> <Th> FMA </Th> <Td> 17640 </Td> </Tr> <Tr> <Td_colspan="2"> Anatomical terminology (edit on Wikidata) </Td> </Tr> <P> The nephron (from Greek νεφρός--nephros, meaning "kidney") is the microscopic structural and functional unit of the kidney . It is composed of a renal corpuscle and a renal tubule . The renal corpuscle consists of a tuft of capillaries called a glomerulus and an encompassing Bowman's capsule . The renal tubule extends from the capsule . The capsule and tubule are connected and are composed of epithelial cells with a lumen . A healthy adult has 0.8 to 1.5 million nephrons in each kidney . Blood is filtered as it passes through three layers: the endothelial cells of the capillary wall, its basement membrane, and between the foot processes of the podocytes of the lining of the capsule . The tubule has adjacent peritubular capillaries that run between the descending and ascending portions of the tubule . As the fluid from the capsule flows down into the tubule, it is processed by the epithelial cells lining the tubule: water is reabsorbed and substances are exchanged (some are added, others are removed); first with the interstitial fluid outside the tubules, and then into the plasma in the adjacent peritubular capillaries through the endothelial cells lining that capillary . This process regulates the volume of body fluid as well as levels of many body substances . At the end of the tubule, the remaining fluid--urine--exits: it is composed of water, metabolic waste, and toxins . </P> <P> Bowman's capsule has a space that collects the filtrate, called Bowman's space; the filtering capillaries of the glomerulus, and the mesangial cells supporting these capillaries . These components function as the filtration unit and make up the renal corpuscle . The filtering structure (glomerular filtration barrier) has three layers composed of endothelial cells, a basement membrane, and podocytes (foot processes). The tubule has five anatomically and functionally different parts: the proximal tubule, which has a convoluted section the proximal convoluted tubule followed by a straight section (proximal straight tubule); the loop of Henle, which has two parts, the descending loop of Henle ("descending loop") and the ascending loop of Henle ("ascending loop"); the distal convoluted tubule ("distal loop"); the connecting tubule, and the collecting ducts . Nephrons have two lengths with different urine concentrating capacities: long juxtamedullary nephrons and short cortical nephrons . </P>

The functional unit of the kidneys is the