What is the main purpose of the capillaries in the body?

The main purpose of capillaries in the body is to allow gas and nutrient exchange. Capillaries are small blood vessels that connect the arterioles and venules. Their thin walls, composed of a single layer of endothelial cells, enable efficient diffusion of oxygen, carbon dioxide, nutrients, and waste products between the blood and surrounding tissues. This exchange process is critical for maintaining cellular function and overall homeostasis in the body.

While other options refer to important biological functions, they do not accurately represent the specific role of capillaries. For example, the connection between muscles and bones is primarily facilitated by tendons, not capillaries. Blood storage occurs mainly in larger vessels and organs such as the spleen, which serves as a reservoir. Nerve impulses are transmitted along neurons and do not take place within the capillary system. Thus, the primary and essential function of capillaries is their involvement in the exchange of gases and nutrients, making them vital to the circulatory and metabolic processes of the body.