What is the primary function of capillaries in the human body?

The primary function of capillaries in the human body is to facilitate nutrient and waste exchange with body cells. Capillaries are the smallest blood vessels and form a network between arteries and veins, allowing for direct contact with tissues. Their thin walls, composed of a single layer of endothelial cells, enable the efficient transfer of oxygen, nutrients, and waste products between the blood and surrounding cells through a process called diffusion. This exchange is crucial for maintaining cellular function and homeostasis.

While capillaries do connect arteries and veins, their primary role is centered on supporting metabolic processes by ensuring that cells receive essential materials and can expel waste efficiently. The other functions listed, such as transporting oxygenated blood and conducting electrical impulses, pertain to other components of the circulatory system and the heart.