Loop of Henle

The loop of Henle is a structure inside the kidney. It is part of the nephron, which helps filter liquid waste from the blood. When people eat food, the body breaks down the food and turns some of it into waste. The nephrons in the kidneys help rid the body of waste. The loop of Henle is important because it helps the body keep the water that it needs to function.

Overview

The loop of Henle is part of the waste-filtering system. The process starts when blood enters the kidney through the renal artery. The blood then passes into smaller blood vessels and eventually into the nephrons. Each nephron has three parts: a renal corpuscle, a renal tubule, and a capillary network. Blood flows from blood vessels into the renal corpuscle. In the corpuscle, waste and water are pushed out of the blood. The waste and water, called filtrate, collect inside the corpuscle. The body needs to rid itself of some of the filtrate. However, it needs to keep some of the water, so the body does not become dehydrated. The loop of Henle is important because it facilitates water reabsorption and contributes to urine concentration.

The loop of Henle is part of the renal tubule. It is a long loop with a descending section and an ascending section. The filtrate first enters the descending part of the loop, which is the thin part of the loop. The loop uses osmosis, which is the movement of water into and out of cells due to differences in the concentrations of water and dissolved solids. As the filtrate moves down the descending loop, water moves outside the loop into the blood. The cells of the descending loop are permeable to water, which means they allow water to move through them. Other parts of the filtrate, such as sodium ions, have limited permeability through the cells of the descending loop. While sodium is reabsorbed, the waste products in the filtrate have to stay inside the loop. This process concentrates the filtrate.

The concentrated filtrate then moves up the thick ascending loop. The cells in the ascending loop are not water-permeable, which means they do not allow water to pass through them. So, the water that has left the loop cannot reenter it. However, the ascending loop does allow some materials, such as sodium ions, to escape. Some of the sodium ions exit the ascending loop, making the fluid around the loop of Henle salty. This is important because the salt in that fluid is what causes water to move out of the descending loop in the first place. Most of the filtrate that was removed in the renal corpuscle is reabsorbed by the body. The concentrated filtrate then moves from the ascending limb of the loop of Henle to the distal convoluted tubule (DCT) before eventually becoming urine and exiting the body.

Bibliography

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Burg, M.B. “Thick Ascending Limb of Henle’s Loop.” Kidney International, vol. 22, no. 5, 1982, pp. 454–64.

Chung, Andrew. “Kidney Anatomy and Function.” Health Pages, 27 June 2022, www.healthpages.org/anatomy-function/kidney. Accessed 21 Mar. 2026.

“41.2 The Kidneys and Osmoregulatory Organs.” LibreTexts Biology, bio.libretexts.org/TextMaps/Map%3A_General_Biology_(OpenStax)/7%3A_Animal_Structure_and_Function/41%3A_Osmotic_Regulation_and_Excretion/41.2%3A_The_Kidneys_and_Osmoregulatory_Organs. Accessed 21 Mar. 2026.

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