Which of the following options shows the correct sequence of the three processes involved in urine formation in the kidneys?

Correct option is A

The correct sequence of the three processes involved in urine formation in the kidneys is:

A. Filtration, Selective Reabsorption, Excretion

Explanation of the Processes:

1. Filtration:

   • The first step occurs in the glomerulus of the nephron, where blood is filtered under high pressure.
   • Waste products, water, ions, and small molecules pass into the nephron, forming a filtrate.
   • Larger molecules like proteins and blood cells are retained in the blood.

2. Selective Reabsorption:

   • In the proximal convoluted tubule, loop of Henle, and distal convoluted tubule, useful substances such as glucose, amino acids, and certain ions are reabsorbed back into the bloodstream.
   • Water is reabsorbed as needed to maintain body fluid balance.

3. Excretion:

   • The remaining filtrate, now called urine, contains waste products such as urea and excess ions.
   • It is transported to the renal pelvis, then to the ureters, stored in the bladder, and eventually excreted via the urethra.

Correct Sequence:

• Filtration ensures that unwanted substances are separated from the blood.
• Selective Reabsorption ensures that essential substances and water are reclaimed by the body.
• Excretion removes the final waste products as urine.