Question

What keeps the capillaries of the vasa recta from dissipating the medullary osmotic gradient?

1) the smooth muscle cells contain Na⁺/K⁺/Cl⁻ cotransporters
2) the smooth muscle cells are impermeable to water and ions
3) the vascular endothelial cells are impermeable to water and ions
4) capillary blood enters and exits the medulla at a similar osmolarity
5) the vascular endothelial cells contain Na⁺/K⁺/Cl⁻ cotransporters

Answer 1

The capillaries of the vasa recta are kept from dissipating the medullary osmotic gradient through mechanisms such as the presence of Na+/K+/Cl- cotransporters in smooth muscle cells, impermeability of vascular endothelial cells to water and ions, and maintenance of similar osmolarity in capillary blood entering and exiting the medulla.

Step-by-step explanation:

The capillaries of the vasa recta are kept from dissipating the medullary osmotic gradient through several mechanisms. One important mechanism is that the smooth muscle cells in the vasa recta contain Na+/K+/Cl- cotransporters, which allow the cells to actively transport sodium, potassium, and chloride ions. This helps maintain the osmolarity of the capillary blood.

Another mechanism is that the vascular endothelial cells of the vasa recta are impermeable to water and ions. This prevents the osmotic gradient from being disrupted by the free movement of water and ions across the capillary walls.

Lastly, the osmolarity of the capillary blood entering and exiting the medulla is maintained at a similar level. This means that the capillaries do not disrupt the osmotic gradient by introducing blood with significantly different osmolarity levels.