Hawaii Massage License Practice Exam

Capillaries are specialized blood vessels that play a critical role in gas exchange within the body. Their structure is uniquely designed to facilitate this process: capillaries have very thin walls, typically one cell layer thick, which allows oxygen and carbon dioxide to easily pass through. This permeability is vital for the efficient exchange of gases; oxygen can diffuse from the blood in the capillaries to the surrounding tissues, while carbon dioxide can move from the tissues back into the blood.

The extensive network of capillaries increases the surface area for gas exchange, ensuring that all cells receive the oxygen they need for metabolism and can effectively eliminate carbon dioxide as a waste product. This adaptation makes capillaries the primary site for respiratory gas exchange, distinguishing them from veins and arteries, which serve different functions within the circulatory system. Veins return blood to the heart, arteries carry blood away from the heart, and arterioles serve as smaller branches of arteries leading into the capillary network. However, the actual exchange of gases occurs exclusively at the level of capillaries.