Fill in the Blank QuestionFill in the blank question.A capillary's wall is made of a single layer of cells.

A capillary's wall is made of a single layer of endothelial cells.

Explanation:

Capillaries are the smallest blood vessels in the body and play a crucial role in the exchange of oxygen, carbon dioxide, nutrients, and waste products between blood and tissues. The thinness of the capillary walls is important because it allows for efficient diffusion of these substances. The endothelial cells that make up this single layer are flattened, enabling the capillaries to be highly permeable. This structure also ensures that blood can flow through the capillaries at a slower rate, facilitating the exchange process. The simplicity of this single-layer design is essential for the capillary’s function within the circulatory system, providing a large surface area relative to volume.