Question

Absorption of ${Na}^{+}$ and $K^{+}$ ions does not occur in

• A. Bowman's capsule
• B. Loop of Henle
• C. Distal convoluted tubule
• D. Proximal convoluted tubule

Answer 1

The correct option is A Bowman's capsule

Urine formation involves three main processes, i.e., filtration, reabsorption and secretion. Filtration is a non-selective process performed by the glomerulus using the glomerular capillary blood pressure. Nearly 99 per cent reabsorption of the filtrate takes place through different parts of the nephrons. Proximal convoluted tubule (PCT) is the major site of reabsorption and selective secretion. Nearly all of the essential nutrients, and 70-80 per cent of electrolytes and water are reabsorbed by this segment. PCT also helps to maintain the pH and ionic balance of the body fluids by selective secretion of hydrogen ions, ammonia and potassium ions into the filtrate and by absorption of HCO3 from it. Henle's loop (HL) primarily helps to maintain osmolar gradient (300 mOsmolL1 -1200 mOsmolL1) within the kidney interstitium. The descending limb of loop of Henle is permeable to water but almost impermeable to electrolytes. This concentrates the filtrate as it moves down. The ascending limb is impermeable to water but allows transport of electrolytes actively or passively. Distal convoluted tubule (DCT) and collecting duct allow extensive reabsorption of water and certain electrolytes, which help in osmoregulation. No reabsorption takes place in the Bowman's capsule.