Why are vasa recta absent in cortical nephrons? A physiological explanation.

Why vasa recta is absent in cortical nephrons?

The vasa recta is a network of blood vessels that surround the loop of Henle in the nephrons of the kidneys. However, the vasa recta is generally absent in cortical nephrons, which are one of the two types of nephrons found in the kidneys.

The main reason for the absence of vasa recta in cortical nephrons is due to their location within the kidney. Cortical nephrons are located in the cortex region of the kidney, which is the outer part. In contrast, juxtamedullary nephrons, the other type of nephrons, are located closer to the medulla region of the kidney, which is the inner part.

The absence of vasa recta in cortical nephrons is a result of differences in their physiological function compared to juxtamedullary nephrons. Cortical nephrons have a shorter loop of Henle that does not extend deep into the medulla. This shorter loop of Henle means that less water and solutes are reabsorbed in the medullary region, resulting in a lower concentration gradient.

Since the vasa recta’s main purpose is to maintain the concentration gradient by removing water and solutes from the renal medulla, it is not necessary in cortical nephrons as their shorter loops of Henle do not rely as heavily on maintaining the concentration gradient.

Instead, cortical nephrons rely on nearby peritubular capillaries to supply blood to the renal cortex. These capillaries receive blood from the efferent arterioles that arise from the glomerulus within the same nephron. The peritubular capillaries facilitate the exchange of substances between the blood and the surrounding tubular structures, such as reabsorption or secretion of various substances.

In summary, the absence of vasa recta in cortical nephrons is due to the location of these nephrons in the kidney and their shorter loop of Henle, which reduces the reliance on maintaining a concentration gradient in the medullary region.

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