Vasa recta (kidney)

Vasa Recta (Kidney)

The vasa recta are a series of straight capillaries in the medulla of the kidney. They lie parallel to the loop of Henle and play a crucial role in the kidney's ability to concentrate urine.

Structure

The vasa recta are part of the renal circulation and are derived from the efferent arterioles of the juxtamedullary nephrons. These capillaries descend into the renal medulla, forming a network around the loop of Henle. The vasa recta are divided into two parts: the descending vasa recta and the ascending vasa recta.

Descending Vasa Recta

The descending vasa recta are thin-walled capillaries that carry blood from the cortex into the medulla. They are permeable to water, allowing water to leave the blood and enter the interstitial fluid of the medulla.

Ascending Vasa Recta

The ascending vasa recta carry blood back towards the cortex. They are less permeable to water but allow solutes to be reabsorbed into the blood, helping to maintain the osmotic gradient in the medulla.

Function

The primary function of the vasa recta is to supply blood to the medulla and to participate in the countercurrent exchange mechanism. This mechanism is essential for the concentration of urine. As blood flows through the vasa recta, it helps to maintain the osmotic gradient established by the loop of Henle, allowing for the reabsorption of water and solutes.

Clinical Significance

The vasa recta are important in the pathophysiology of certain kidney diseases. For example, damage to these capillaries can lead to impaired urine concentration and contribute to conditions such as acute kidney injury.

Related Pages

• Nephron
• Loop of Henle
• Renal circulation
• Countercurrent exchange

References

Diagram of a kidney nephron, showing the vasa recta.