Nephron Loop (Loop of Henle)

ansa nephroni (Henle)

The nephron loop, or loop of Henle, is the hairpin-shaped part of the tubule that dips from the cortex into the medulla and back. Its descending limb lets water out, while the thick ascending limb pumps salt out but stays watertight. This arrangement builds the salt gradient the kidney needs to concentrate urine.

Anatomical Data

Structure & Supply

Location	Extends from the cortex into the renal medulla and back
Parts	Thick descending limb Thin descending limb Thin ascending limb Thick ascending limb
Blood Supply	Vasa recta; Peritubular capillaries
Venous drainage	Vasa recta

Biomechanics

Function & Actions

Creates the medullary salt gradient by countercurrent multiplication, allowing the kidney to produce concentrated or dilute urine as needed.

Clinical Relevance

Clinical Notes

Loop diuretics such as furosemide block the salt pump (NKCC2) in the thick ascending limb, producing a strong diuresis used for heart failure and fluid overload. Long loops belong to juxtamedullary nephrons near the medulla. Inherited defects in the loop's transporters cause Bartter syndrome.

Pathology

Common Injuries & Conditions

Bartter Syndrome

An inherited defect in salt transport in the thick ascending limb, causing salt wasting, low potassium and alkalosis.

Diuretic-Induced Electrolyte Loss

Loop diuretics can cause low potassium, low sodium and dehydration if not monitored.

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