Describe the Process of Urine Formation in Kidneys Class 10

• 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.

Also Check – Function of Nephrons

3 Steps of Urine Formation

The following 3 steps are involved in the process of Urine formation

1. Ultrafiltration
2. Selective reabsorption
3.  Tubular secretion

Also Check – How is the Amount of Urine Produced Regulated ?

Ultrafiltration

•  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.

Also Check- Structure of Kidney 

 Selective reabsorption

•  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.

Also Check – Function Of Kidney

 Tubular secretion

•  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.