What role do capillaries play in the circulatory system?

Capillaries play a crucial role in the circulatory system by facilitating gas and nutrient exchange between the blood and surrounding tissues. These tiny blood vessels have thin walls, which allow for the efficient transfer of oxygen, carbon dioxide, nutrients, and waste products. The large surface area provided by the extensive network of capillaries ensures that nearly every cell in the body can access the nutrients it requires while also allowing for the removal of metabolic waste.

Unlike arteries and veins, which primarily function to transport blood, capillaries are specifically designed for this exchange process. This is why their structure is adapted to be very thin-walled and highly permeable, making them ideally suited for their role in the microcirculation of blood.

While other vessels like arteries and veins have significant roles, maintaining pressure or serving as blood reservoirs, capillaries are uniquely positioned as the site of critical exchange that sustains cellular functions throughout the body.