Each kidney has nearly one million complex tubular structures called nephrons.
The nephron is a functional unit of kidneys.
Each nephron has two parts
Glomerulus
Renal tubule
Glomerulus: It is tuft of capillaries formed by the afferent arterioles and efferent arterioles.
The renal tubule: It begins with a double walled cup-like structure called Bowman’s capsule that encloses the glomerulus. Glomerulus alongwith Bowman’s capsule, is called the malpighian body or renal corpuscle.
The tubule continues further to form a highly coiled network – proximal convoluted tubule(PCT). A descending and ascending limb, hairpin shaped Henle’s loop is the next part of the tubule. The ascending limb continues as another highly coiled tubular region called distal convoluted tubule (DCT).
The DCTs of many nephrons open into a straight tube called collecting duct, many of which converge and open into the renal pelvis through medullary pyramids in the calyces.
The Malpighian corpuscle, PCT and DCT of the nephron are situated in the cortical region of the kidney whereas the loop of Henle dips into the medulla.
The efferent arteriole emerging from the glomerulus forms a fine capillary network around the renal tubule called the peritubular capillaries. A minute vessel of this network runs parallel to the Henle’s loop forming a ‘U’ shaped vasa recta. Vasa recta is absent or highly reduced in cortical nephrons.
Functioning of nephrons:
Glomerular filtration: 1100-1200ml of blood filtered by our kidney per minute. The glomerular capillary blood pressure causes filtration of blood through three layers: endothelium of glomerular blood vessels, epithelium of Bowman’s capsule and basement membrane between these two layers.Ultrafiltration of blood is seen here due to the finely filtered blood.