How do capillaries function within the circulatory system?

Capillaries play a crucial role in the circulatory system, primarily through the exchange of oxygen, nutrients, and waste products between the blood and the body’s tissues. These tiny blood vessels connect arterioles (which carry blood away from the heart) and venules (which return blood to the heart). The walls of capillaries are thin and permeable, allowing for efficient transfer of gases, nutrients, and other substances. This exchange occurs via diffusion — oxygen and nutrients pass from the blood into the tissue cells, while carbon dioxide and waste products move from the cells into the blood.

Understanding the function of capillaries highlights their importance in maintaining homeostasis within the body, as they ensure that tissues receive the necessary substances while removing waste. This process is vital for cellular respiration and overall metabolic function. Other options such as carrying blood away from the heart or returning it to the heart relate to the roles of arteries and veins respectively, while controlling blood pressure is managed predominantly by larger blood vessels and associated mechanisms within the cardiovascular system.