- Urine is formed in the nephrons of kidneys.
- Each kidney contains a large number of tiny filtration units called nephrons.
- Blood at high pressure flows into these tubules by blood capillary’s called glomerulus which are surrounded by Bowman’s capsule.
The following steps are involved in the process of urine formation
- Blood enters the glomerulus through the afferent arterioles.
- It passes under high pressure that results in filtration of blood. Water and small molecules are forced out of glomerular capillary walls and Bowman’s capsule
- Large molecules remain in the blood of the glomerulus.
- Some molecules are selectively reabsorbed into the blood.
- The glomerular filtrate flows through the tubular parts of U-shaped Henle’s loop.
- The useful substances such as glucose amino acids and salts which give energy are reabsorbed by a process called selective reabsorption.
- Hence the filtrate now contains Urea, Some salts and water.
- Reabsorption of solutes increases the water concentration of the filtrate.
- Water is then reabsorbed into blood by osmosis.
- Some nitrogenous waste products and some other substances are removed from blood by parts of Henle’s loop and are passed to blood.
- The urine formed in each kidney enters a long tube called the ureter. Which connects the kidneys with the urinary bladder.
- The urine thus formed is collected in the urinary bladder.
- Urine is stored in the urinary bladder until the pressure of the expanded bladder causes the urge to pass it out through the urethra.