Vasa recta

Definition

The vasa recta are a series of straight capillaries in the medulla of the kidney that play a crucial role in concentrating urine. They are part of the countercurrent exchange system, which helps maintain the osmotic gradient essential for water reabsorption.

5 Must Know Facts For Your Next Test

1. The vasa recta run parallel to the loops of Henle in the nephron.
2. They are responsible for maintaining the medullary concentration gradient by exchanging water and solutes with surrounding interstitial fluid.
3. The descending vasa recta lose water and gain solutes as they descend into the medulla, while the ascending vasa recta gain water and lose solutes as they ascend back towards the cortex.
4. They work closely with the loops of Henle to facilitate the reabsorption of water and concentrate urine.
5. Any disruption in vasa recta function can lead to an inability to concentrate urine, resulting in conditions such as diabetes insipidus.

Review Questions

• What is the primary function of the vasa recta in kidney physiology?
• How do the descending and ascending portions of the vasa recta differ in their interactions with water and solutes?
• Why is it important for the vasa recta to maintain a countercurrent exchange system?

Related terms

Nephron: The functional unit of the kidney responsible for filtering blood and forming urine.

Loop of Henle: A segment of the nephron that creates a concentration gradient in the medulla, facilitating water reabsorption.

Countercurrent Exchange System: A mechanism involving fluid flow in opposite directions that maximizes transfer efficiency, crucial for concentrating urine in kidneys.