How do capillaries function in blood circulation?

Capillaries play a crucial role in the circulatory system by facilitating the exchange of nutrients, gases, and waste products between blood and tissues. These small, thin-walled blood vessels connect arterioles and venules, providing a large surface area for this exchange to occur efficiently. As blood flows through the capillaries, oxygen and nutrients from the blood diffuse into the surrounding tissues, while carbon dioxide and metabolic waste products move from the tissues into the bloodstream. This process is vital for maintaining homeostasis and ensuring that body cells receive the substances they need for proper function while removing harmful waste.

Other options, while related to blood circulation, do not accurately describe the primary function of capillaries. For example, carrying blood to the heart pertains to larger blood vessels, such as veins, and does not occur in capillaries. Similarly, storing blood is not a function of capillaries; instead, blood storage is primarily the role of organs like the spleen and liver. Regulating blood pressure is managed by the heart and the larger arterial system, particularly the arteries and arterioles, rather than by the capillaries.