Question

$HC{O}_3^{-}$ absorption takes place in

• A. proximal convoluted tubule and distal convoluted tubule
• B. distal convoluted tubule and collecting duct
• C. proximal convoluted tubule and Henle’s loop
• D. Henle’s loop and collecting duct

Answer 1

The correct option is A proximal convoluted tubule and distal convoluted tubule

Urine formation involves three processes - ultrafiltration, reabsorption and secretion. Reabsorption is necessary to prevent loss of essential nutrients in urine. Around 99 percent of filtrate formed is reabsorbed. Reabsorption can take place in different segments of nephron.

Nearly all of the essential nutrients and 70-80 percent of electrolytes and water are reabsorbed by proximal convoluted tubule (PCT). PCT is the highly coiled structure found next to Bowman’s capsule. PCT is also involved in absorption of $HC{O}_3^{-}$ from filtrate.

Distal convoluted tubule (DCT) is another highly coiled tubule which finally opens into collecting duct. DCT is involved in reabsorption of $HC{O}_3^{-}$ and conditional reabsorption of $N{a}^{+}$ and water.

Henle’s loop is not much involved in reabsorption of $HC{O}_3^{-}$.

Large amount of water is reabsorbed in collecting duct.