Kaplan Nursing Entrance Practice Exam

What best describes capillaries in terms of their walls?

1. Thick and muscular

2. Thin and permeable

3. Elastic and rigid

4. Thick and impermeable

The correct answer is: Thin and permeable

Capillaries are best described as having thin and permeable walls. This characteristic is essential because it allows for the efficient exchange of substances between the blood and the surrounding tissues. The thinness of the capillary walls, which are only a single cell layer thick, facilitates the diffusion of oxygen, carbon dioxide, nutrients, and waste products. This permeability is crucial for metabolic processes, as it enables cells to receive the oxygen and nutrients they need while also removing waste products effectively. The other descriptions do not accurately reflect the structure or function of capillaries. For instance, thick and muscular walls are more characteristic of arteries, which need to withstand higher pressure. Elastic and rigid walls would not allow for the flexibility or exchange required in the capillary network. Similarly, thick and impermeable walls would hinder the essential exchange processes that capillaries are designed to facilitate.