Vasa recta (kidney)

Diagram of a kidney nephron, showing the vasa recta.

The vasa recta are a series of straight capillaries in the kidney that lie parallel to the loop of Henle. They are part of the renal circulation and play a crucial role in the concentration of urine.

Structure

The vasa recta are formed from the efferent arterioles of the juxtamedullary nephrons. These arterioles descend into the renal medulla, where they form a series of hairpin loops. The descending and ascending limbs of these loops run parallel to the loop of Henle, allowing for efficient exchange of solutes and water.

Function

The primary function of the vasa recta is to maintain the osmotic gradient in the renal medulla. This gradient is essential for the kidney's ability to concentrate urine. As blood flows through the vasa recta, it exchanges water and solutes with the surrounding interstitial fluid, a process known as countercurrent exchange. This mechanism helps to preserve the high osmolarity of the medulla, which is necessary for water reabsorption in the collecting duct.

Clinical significance

Disruption of the vasa recta's function can lead to renal medullary hypoxia and contribute to conditions such as acute kidney injury. Understanding the role of the vasa recta is important in the context of hypertension and diabetes mellitus, as these conditions can affect renal blood flow and the kidney's ability to concentrate urine.

Related pages

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