Describe internal structure of nephron.

Each nephrons has two parts:

$(1)$ Malpighian Body and $(2)$ Uriniferous Tubule

Each nephrons is approximate $3 \mathrm{~cm}$. in length and $20-30 \mu \mathrm{m}$ width.

$(1)$ Malpighian Body : It is complex structure formed of glomerulus and Bowman's capsule.

Malpighian body (renal corpuscle)

$(i)$ Glomerulus is a tuft of capillaries formed by the afferent arterioles - fine branch of renal artery. Blood from the glomerulus is carried away by efferent arteriole.

- Diameter of efferent arteriole is smaller than afferent arteriole. Blood is filtered in the glomerulus.

$(ii)$ Bowman's Capsule one side of closed uriniferous tubule, invaginate to form cup shaped double walled sac like structure known as Bowman's capsule.

- Outer wall of Bowman's capsule is formed of squamous epithelium, while inner side possess specific cells called podocyte. It by special arrangement forms filteration pore, allows the molecules to pass through it.

Bowman's capsule and glomerulus togather termed as malpighian body.

$(2)$ Uriniferous Tubule : Immediate part after the malpighian body/corpuscle is known as neck region.

$(i)$ Proximal Convoluted Tubule is highly coiled structure ($PCT$).

$(ii)$ Loop of Henle : It is hairpin shaped region after $PCT$. It has ascending and descending limbs.

Ascending limb continues as another highly coiled tubular region called distal convoluted tubule $(\mathrm{DCT})$

A diagrammatic representation of a nephron showing blood vessels, duct and tubule

- Distal convoluted tubules of many nephrons open into a straight tube called collecting duct.

- Many $DCTs$ converge and open into large duct of Bellini (Bellini's duct).

$=$ It opens into the renal pelvis through medullary pyramids in the calyces.

Urine formed by all excretory unit is emptied into renal pelvis.

- Synthesis of urine occurs only in the excretory unit (nephron). Collecting tubule transports the urine and it is eliminated through renal pelvis.