Nephrons:

It is the structural and functional unit of a kidney. It is a tube like structure. They increase surface area in kidney for more urine formation and for efficient exchange of materials in a kidney.

Nephrons are of 2 types:

 

Cortical Nephrons	Juxta-medullary Nephrons
Form 80% of total nephrons in each kidney.	Form 20% of total nephrons in kidney.
Small in size.	Large in size.
Lies mainly in cortex. (more coiled)	Lies mainly in medulla and at function between cortex and medulla. (less coiled)
They control blood plasma volume when water supply is normal.	They control plasma supply when water supply is short.

Structure of nephron: It has 4 regions Bowman’s capsule, PCT (Proximal Convoluted Tubule), DCT (Distal Convoluted tubule), loop of Henle, and collecting ducts. 

1. Bowman’s capsule: It is a double walled cup and starting part of nephron. It contains glomerulus in its centre. Glomerulus has 50 small capillaries. Bowman’s capsule and glomerulus both are combinely known as Malphigian body.   
2. Proximal Convoluted tubule PCT: Starts from lower part of Bowman’s capsule. It is a hollow coiled tubular part of nephrons, lies in renal cortex.
3. Loop of Henle: U shaped tubule, located in renal medulla. It has two limbs, one ascending and other ascending limb.
4. Distal convoluted tubule: It is also coiled, lies in renal cortex. It starts from the end of ascending limb of loop of Henle.
5. Collecting tube: The larger tubule of nephron where urine is collected.