Draw a neat and labelled diagram of an excretory unit (nephron).

(N/A) Each nephron consists of two main parts:
$(1)$ Malpighian body (Renal corpuscle) and $(2)$ Renal tubule.
Each nephron is approximately $3 \ cm$ in length and $20-30 \ \mu m$ in width.
$(1)$ Malpighian body: It is a complex structure formed by the glomerulus and Bowman's capsule.
$(i)$ Glomerulus: It is a tuft of capillaries formed by the afferent arteriole,which is a fine branch of the renal artery. Blood from the glomerulus is carried away by the efferent arteriole.
- The diameter of the efferent arteriole is smaller than that of the afferent arteriole,which helps in the filtration of blood in the glomerulus.
$(ii)$ Bowman's capsule: It is a cup-shaped,double-walled sac that encloses the glomerulus. The outer wall is composed of squamous epithelium,while the inner wall contains specialized cells called podocytes. These cells are arranged in an intricate manner to form filtration slits (or filtration pores),which allow the passage of molecules.
$(2)$ Renal tubule: The part of the nephron immediately following the Malpighian body is the proximal convoluted tubule $(PCT)$,which is a highly coiled structure.
$(i)$ Loop of Henle: It is a hairpin-shaped region following the $PCT$. It consists of a descending limb and an ascending limb.
$(ii)$ Distal convoluted tubule $(DCT)$: The ascending limb continues into another highly coiled tubular region called the $DCT$.
- The $DCT$ of many nephrons opens into a straight tube called the collecting duct.
- Many collecting ducts converge and open into the renal pelvis through medullary pyramids in the calyces.
- Urine formation occurs in the nephron,while the collecting duct transports the urine to the renal pelvis for elimination.