Thick ascending limb of loop of Henle
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| Thick ascending limb of loop of Henle | |
|---|---|
 | |
| Scheme of renal tubule and its vascular supply. (Labeled at center left.) | |
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| Nephrons | |
| Latin | tubulus rectus distalis |
| Gray's | subject #253 1223 |
| Dorlands/Elsevier | t_22/12830078 |
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Overview
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 block the K+/Na+/2Cl- co-transporter.
Urea which remains in the loop creates a solute potential that prevents water completely osmosing out into the interstitial space. This means that while almost all the ions are reabsorbed, there will still be some water in the urine, and hence, the concentration of the filtrate in the loop is decreased here. (If only ions were present, and a certain amount of ions were reabsorbed, one would expect the same amount of the water to be reabsorbed too, and hence the concentration would remain the same, but this is not true.)
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.
External links
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 As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
ja:ヘンレ係蹄太い上行脚
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
