Which of the following functions in separating the interstitial fluid from the blood plasma?

The blood vessel walls serve as a crucial barrier that separates interstitial fluid from blood plasma. These walls are composed of endothelial cells that line the interior of blood vessels, maintaining a selective permeability that allows for the controlled exchange of substances between the blood and surrounding tissues. This exchange is vital for various functions, including nutrient delivery, waste removal, and fluid balance.

While cell membranes do play a role in maintaining the internal environment of individual cells and separating the intracellular fluid from the extracellular fluid, they do not specifically delineate the interstitial fluid from blood plasma on a systemic level.

Lymphatic vessels, on the other hand, are part of the immune system and help in draining excess interstitial fluid, but they do not directly separate plasma from interstitial fluid. They function more in the transport of lymph, which includes proteins and other materials that have escaped the circulatory system.

The dermis layer is a part of the skin that provides structural support and contains connective tissues, but it does not have a direct role in separating interstitial fluid from blood plasma. It does not function as a barrier between these two fluid compartments in the way blood vessel walls do.

Thus, the blood vessel walls are specifically designed to create a boundary that is essential for maintaining proper