Thick ascending limb of loop of Henle: Information from Answers.com

Thick ascending limb of loop of Henle

Scheme of renal tubule and its vascular supply. (Labeled at center left.)

Nephron. Diagram is labeled in Polish, but ion flow can still be identified.
Latin	tubulus rectus distalis
Gray's	subject #253 1223

The thick ascending limb of loop of Henle (or distal straight tubule) is a segment of the nephron in the kidney. It can be divided into two parts: that in the renal medulla, and that in the renal cortex.

Medullary thick ascending limb

The medullary thick ascending limb remains impermeable to water. Sodium, potassium (K⁺) and chloride (Cl^-) ions are reabsorbed by active transport. K⁺ is passively transported along its concentration gradient through a K⁺ leak channel in the apical aspect of the cells, back into the lumen of the ascending limb. This K⁺ "leak" generates a positive electrochemical potential difference in the lumen. The electrical gradient drives more reabsorption of Na⁺, as well as other cations such as magnesium (Mg²⁺) and importantly calcium Ca²⁺.

Loop diuretics such as furosemide block the K⁺/Na⁺/2Cl^- co-transporter.

This is also the part of the tubule that generates Tamm-Horsfall protein. The function of this protein is not well understood, but is responsible for creating urinary casts.

Cortical thick ascending limb

The difference between the medullary and cortical thick ascending limbs is mainly anatomical. Functionally, they are very similar.

The cortical thick ascending limb drains urine into the distal convoluted tubule.

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This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated.

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v • d • e Urinary system – Kidney

Layers	Renal fascia • Renal capsule • Renal cortex (Renal column) • Renal medulla (Renal sinus, Renal pyramids, medullary interstitium) • Renal lobe • Cortical lobule • Medullary ray • Nephron

Afferent circulation	Renal artery → Segmental arteries → Interlobar arteries → Arcuate arteries → Interlobular arteries → Afferent arterioles → Renal corpuscle (Glomerulus, Bowman's capsule)

Renal tubule	Proximal tubule → Loop of Henle (Descending, Thin ascending, Thick ascending) → Distal convoluted tubule → Connecting tubule → Collecting ducts aka Duct of Belini → Renal papilla → Minor calyx → Major calyx → Renal pelvis → Ureter

Efferent circulation	Glomerulus → Efferent arterioles → Peritubular capillaries / Vasa recta → Arcuate vein → Interlobar veins → Renal vein

Juxtaglomerular apparatus	Macula densa • Juxtaglomerular cells • Mesangium/Extraglomerular mesangial cell

Filtration	Glomerular basement membrane • Podocyte • Filtration slits • Mesangium/Intraglomerular mesangial cell • Tubular fluid

Renal physiology	Acid base physiology • Fluid balance

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