Describe the structure of human excertory system with suitable diagram. Add a note on the process of urine formation.

Explanation

For diagram, Human excretory system consists of the following organs, viz. a pair of kidneys, a pair of ureters, a single unpaired urinary bladder,urethra in males or vestibule in females.
1. Kidney:
(1) The kidneys are dark red, bean-shaped organs about 10 cm long, 5 cm wide and 4 cm thick.
(2) Each kidney is convex on lateral margin. There is a notch called hilus present on the medial surface. Blood vessels, nerves and ureters enter and leave the kidney through hilus. They are concerned with excretion and osmoregulation.
2. Ureters :Ureters are a pair of narrow ducts about 40 cm long, each coming out of kidney through the hilus and opening in urinary bladder. They carry urine from the kidneys to urinary bladder by peristaltic contractions.
3. Urinary Bladder: Urinary bladder is a single pear-shaped structure with thick muscular wall that is lined by transitional epithelium and a thick layer of detrusor muscle. It stores 500 ml to 1 litre urine temporarily. Urine is expelled out at intervals through urethra.
4. Urethra : Urinary bladder opens into urethra. The urethral opening is guarded by urethral sphincter which is under voluntary control. Urination or micturition is the process of emptying the urinary bladder.