Generally, mammals have a pair of bran-shaped kidneys. The mammalian kidney has 2 distinct regions, an outer renal cortex and inner renal medulla. Both regions are packed with microscopic excretory tubules, nephrons, and their associated blood vessels. Each nephron consists of a single long tubule and a ball of capillaries, known as glomerulus. The blind end of the tubule forms a cup-shaped swelling called Bowman’s capsule, that surround the glomerulus. From Bowman’s capsule, the filtrate passes through 3 regions of the nephron which are proximal tubule, the loop of Henle. A hairpin turns with a descending limb and an ascending limb and the distal tubule. The distal tubule empties into a collecting duct, which receives processed filtrate from many nephrons. The many collecting ducts empty into the renal pelvis, which is drained by ureter.
For the structure of nephron, each nephron is supplied with blood by an afferent arteriole, a branch of the renal artery that subdivides into the capillaries of the glomerulus. The capillaries converge as they leave the glomerulus, forming an efferent arteriole. It is surrounded by the Bowman’s capsule. The double-walled epithelial Bowman’s capsule is formed by the invagination of the blind end of the nephron. The glomerulus and Bowman’s capsule form the first region of the nephron and is known as the renal corpuscle or the Malpighian body. The capillary walls are composed of a single layer of endothelial cells with openings between them with a diameter 50-100nm. These cells are pressed up against basement membrane which completely envelops each capillary, separating the blood in the capillary from the lumen of Bowman’s capsule. The inner layer of the Bowman’s capsule is composed of a cell called podocytes which have arms that give off structures resembling tube-feet called foot processes or secondary processes. The secondary processes support the basement membrane and capillaries beneath it and gaps between the processes (slit pores) facilitate the process of filtration. The Malpighian body leads into the remainder of the tubule.
