What is a nephron made of?
Nephron is a convoluted tubule which is blind at one end and ends to open in another duct. Different types of epithelial tissues form different parts of the tubule. Blood vessels are intimately associated with nephron.
Nephron is structural and functional unit of kidney: in human, one kidney has upto one million nephrons.
The structural association of nephron and blood vessels primarily help in filtration of blood to remove nitrogenous waste products.
Nephron selectively reabsorbs materials from filtrate which are not supposed to be excreted and these materials re-enter blood circulation.
There is also tubular secretion by nephron which helps in maintaining pH of blood.
Different parts of nephron are:
- Bowman's capsule
- Proximal Convoluted Tubule (PCT)
- Loop of Henle-- Descending limb and Ascending limb
- Distal Convoluted Tubule (DCT)
Bowman's capsule is cup shaped with inner visceral layer, it is closely associated with a tuft of capillaries (=glomerulus). This layer is made of special cells (with cytoplasmic processes) called PODOCYTEs which surround the capillaries forming a sieve. Filtration takes place across visceral membrane. Outer parietal layer of capsule's cup is made of squamous epithelium.
Except descending limb of Henle, lining of all other parts are made of CUBOIDAL epithelium . In PCT, the cuboidal epithelium is brush bordered, due to presence of microvilli at free ends of the cells, to increase surface area for reabsorption.
Tubular secretion takes place mainly along DCT.
Water reabsorption from urine continues beyond its passage through nephron, in the collecting tubules.