What is the smallest type of blood vessel that facilitates gas exchange?

Capillaries are the smallest type of blood vessel in the circulatory system and play a crucial role in gas exchange. Their thin walls, consisting of a single layer of endothelial cells, allow for the efficient diffusion of oxygen and carbon dioxide between the blood and surrounding tissues. This exchange is essential for maintaining cellular respiration and overall metabolism in the body.

Capillaries connect arterioles (small arteries) and venules (small veins), creating a network that reaches nearly every cell. This extensive network increases the surface area for gas exchange and ensures that oxygen can be delivered effectively, while carbon dioxide and other metabolic waste can be removed.

The other options refer to different types of blood vessels. Arteries are responsible for carrying oxygenated blood away from the heart under high pressure, while veins transport deoxygenated blood back to the heart. Aneurysms relate to the pathological dilation of a blood vessel and are not a type of blood vessel but rather a condition.