Topics:
Animal Physiology, Animal Refresher
Site of Maximum Tubular Reabsorption in Kidney
Maximum tubular reabsorption (about 80%) occurs at:
- Proximal Convoluted Tubule (PCT) — Correct Answer
- Loop of Henle
- Distal Convoluted Tubule (DCT)
- Collecting Duct
Explanation:
Correct Answer: Proximal Convoluted Tubule (PCT)
About 80% of tubular reabsorption occurs in the Proximal Convoluted Tubule (PCT). This includes reabsorption of water, sodium, glucose, amino acids, bicarbonate, potassium, calcium, and urea.
Reabsorption at PCT — Key Details
- ~65–80% of filtered Na⁺, K⁺, Ca²⁺, water, and solutes are reabsorbed here
- Glucose and amino acids: Reabsorbed by co-transport with Na⁺ (active transport) — completely reabsorbed in normal conditions
- Glucose transport protein: SGLT (Na⁺-glucose cotransporter) in luminal membrane; GLUT-2 in basolateral membrane
- PCT cells have a brush border (microvilli) to increase surface area for reabsorption
Reabsorption at Other Segments
- Loop of Henle (Thin descending): Permeable to water, impermeable to solutes — water exits
- Loop of Henle (Ascending): Permeable to solutes (Na⁺, K⁺, Cl⁻), impermeable to water
- DCT & Collecting Duct: Fine-tuning of Na⁺ (aldosterone) and water (ADH) reabsorption
Clinical Note
In diabetes mellitus, when blood glucose exceeds the renal threshold (~180 mg/dl), the PCT's transport capacity is overwhelmed, leading to glycosuria (glucose in urine).
📚 About this Topic — Animal Physiology
This multiple choice question is from Animal Physiology, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Physiology to strengthen your preparation.
