Nephrons- the functional unit of Kidney
The structural and functional unit of kidney is called ‘Nephron’. There are millions of nephron in each kidney of human being. Nephron performs the excretory function as well as osmoregulation.
Structure of Nephron:
The nephron or uriniferous tubule is the functional unit of the kidney. Each kidney of man is about the length of 3 cm.
There are following main parts of naphron:
(a) Bowman’s capsule
(b) Proximal convoluted tubule (PCT)
(c) Loop of Henle
(d) Distal convoluted tubule (DCT)
(e) Collecting Duct
The nephron begins as a spherical structure called malpighian body. The malpighian body composed of cup like “Bowmen’s Capsule”. It is consists of double walls. The outer wall is continuous with the rest of the nephrons. The bowmen capsule contains the rich network of capillaries known as ‘glomerus’. It lies in the renal cortex of the kidney. The Bowman’s capsule is not the only body which composes the malpighian body. Bowman’s capsule together with glomerulus composes the renal corpuscle or malpighian body.
Proximal Convoluted tubule:
It is a coiled tubule arises from bowman capsule. It also lies in renal the cortex. It is also attached with capillaries. Its wall is of a single layer of columnar cells which have a lot of microvilli on its surface.
Loop of Henle:
The proximal tubule narrows and descents down in medulla and make U-shaped tube that again comes back in the cortex. This tube is known as the loop of henle. It has a descending and an ascending limb. The descending limb of loop of henle is a continuation of the Proximal convoluted tubule it and enters into the renal medulla. The ascending limb reenters the renal cortex and joins the Distal convoluted Tubule.
Distal Convoluted Tubule:
The part where the ascending limb of the loop of henle becomes coiled and lies in the cortex, it is called Distal convoluted Tubule. It is greatly twisted just like Proximal convoluted tubule. This tubule opens into the collecting duct.
The distal convoluted tubule opens into a common duct called collecting duct. It receives urine from several nephrons then runs through the medullary pyramids and opens into the pelvis of the kidney.
The gomerulus is carried by “efferent artride” to two capillary networks. The first capillary network is called peritubular capillaries associated with proximal convoluted tubule and distal convoluted tubule. The second capillary network is called vasa recta that runs parallel besides the loop of henle.