Descending limb of loop of Henle

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Descending limb of loop of Henle
Gray1128.png
Scheme of renal tubule and its vascular supply. (Labeled at center left.)
Nefron.png
Nephron. Diagram is labeled in Polish, but ion flow can still be identified.
Gray's subject #253 1223
Dorlands/Elsevier l_10/12493919

The descending limb of loop of Henle is the portion of the renal tubule constituting the first part of the loop of Henle.

Physiology

The permeability is as follows:

Substance Permeability
ions Low permeability. Sodium and chloride ions do not easily pass through. [1]
urea Moderate permeability.[2]
water Highly permeable. Water is readily reabsorbed from the descending limb by osmosis.[3]

Also, the medullary interstitium is highly concentrated (because of the activity of the ascending limb), leading to a strong osmotic gradient from the descending limb to the medulla.

Because of these factors, the concentration of the urine increases dramatically in the descending limb. Osmolality can reach up to 1400 mOsmol/kg by the end of the descending limb.[3]

Histology

The epithelium is low simple cuboidal.[4]

They can be distinguished from the vasa recta by the absence of blood, and they can be distinguished from the thick ascending limb by the thickness of the epithelium.[5]

Nomenclature

Like the ascending limb, the descending limb has thick and thin portions. However, this distinction is not as important physiologically as in the ascending limb, so often the two are treated as one structure. The thick descending limb is less important than the thin descending limb, so often the terms "descending limb" and "thin descending limb" are used interchangeably.

Some sources simply refer to a "thin limb". In this context, the thin ascending limb of loop of Henle would be included.

Additional images

References

  1. http://clem.mscd.edu/~raoa/bio2320/uriphys/sld019.htm
  2. Essentials of Human Physiology by Thomas M. Nosek. Section 7/7ch08/7ch08p09.
  3. 3.0 3.1 Essentials of Human Physiology by Thomas M. Nosek. Section 7/7ch07/7ch07p09.
  4. Organology at UC Davis Urinary/mammal/medulla/medulla1 - "Mammal, kidney medulla (LM, Medium)"
  5. Histology image: 15804loa – Histology Learning System at Boston University

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 As such, some of the information contained herein may be outdated.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.


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