Mention the pathway of urine starting from the organ of its formation. Name 4 substances which are reabsorbed from the initial filtrate in the tubular part of the nephron. ( CBSE 2011, 2012)

The basic structural and functional unit of the kidney is Nephrons in which the formation of urine starts. The formation of urine occurs by the three processes:

1. Glomerular filtration

2. Tubular reabsorption and

3. Tubular secretion.

GLOMERULAR FILTRATION:

The filtration of blood takes place in bowman’s capsules from the capillaries of glomerulus. This filtrate then passes to the tubular part of the nephron. This filtrate contains glucose, amino acids, urea, uric acid, salts, and water.

TUBULAR FILTRATION:

In the tubular part, useful substances are selectively reabsorbed into the blood capillaries surrounding the nephron tubules. The substances such as glucose, amino acids, salts, and water are reabsorbed in this step.

TUBULAR SECRETION:

The filtrate which remains after reabsorption is called urine. The collecting duct collects the urine from the nephron and carries it to the long tube Ureter which connects kidneys to the Urinary Bladder. Urine is stored there until the pressure of expanded bladder leads to the urge to pass it through the Urethra.

4 substances that are reabsorbed from the initial filtrate in the tubular part of the nephrons are Glucose, Amino acids, salts, and water.