Nephron : A nephron is a structural and functional unit of kidney. It is differentiated into four regions Bowman's capusle, proximal convoluted tubule, loop of Henle and distal convoluted tubule (DCT).

Fig. Uriniferous tubule

(i) Bowman's capsule : It is a double walled cup containing bunch of parallel capillaries called glomerulus. The glomerulus rests on basement membrane. It is a continuous layer. The Bowman's capsule and glomerulus together are called renal corpuscle or malpighian body. The endothelial cells lining the glomerulus have pores  between them. The cells of inner wall of Bowman's capsule are called podocytes have gaps called slit pores 25nm wide between them.

The glomerulus is supplied by an afferent arteriole and is drained by a relatively narrow efferent arteriole. The latter forms peritubular capillary network around the rest of nephron.

(ii) Proximal convoluted tubule (PCT) : It starts from the neck of the Bowman's capsule.

(iii) Loop of Henle : It is a U-shaped segment of the nephron located in the renal medulla. It consists of two straight parallel limbs.

(iv) Distal convoluted tubule (DCT) : Like PCT, it is greatly twisted and lies in the renal cortex. DCT continues into a collecting tubule.

Collecting tubes or ducts : These are larger tubes, each receiving the collecting tubule of several nephrons. They join each other forming larger ducts of bellini. These open into calyces, which lead into the pelvis.