Topics:
Animal Physiology, Animal Refresher
Loop of Henle Lumen Diameter
The thin descending limb, thin ascending limb and thick ascending limb of loop of Henle:
- Have same lumen diameter — Correct Answer
- Have same epithelial cell thickness
- Have lumen diameter corresponding to the limb being thin or thick
- None of the above
Explanation:
Correct Answer: Have same lumen diameter
A common misconception is that the 'thin' and 'thick' limbs of the loop of Henle differ in their lumen diameter. In reality, all limbs have the same lumen diameter. The terms 'thin' and 'thick' refer to the thickness of the epithelial cells lining the limbs, not the lumen.
Clarification
- Thin limb: lined by thin, squamous epithelial cells (low metabolic activity, no active transport).
- Thick limb (Thick Ascending Limb, TAL): lined by thick, cuboidal epithelial cells (high metabolic activity, active ion transport).
- Lumen diameter is equal across all limbs — only epithelial cell thickness differs.
Functional Differences
- Descending thin limb: Permeable to water, impermeable to solutes — water exits, concentrating tubular fluid.
- Ascending limb (thin + thick): Impermeable to water, permeable to solutes — ions exit, diluting tubular fluid.
- TAL: Site of action of loop diuretics (furosemide) — inhibits Na⁺-K⁺-2Cl⁻ cotransporter.
📚 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.
