Which blood vessel system is responsible for the exchange of gases at the tissue level?

The capillary system is essential for the exchange of gases at the tissue level due to its unique structure and function. Capillaries are the smallest blood vessels and have thin walls, which consist of a single layer of endothelial cells. This design facilitates efficient diffusion, allowing oxygen and carbon dioxide to move between the blood and surrounding tissues.

In the capillaries, oxygen is released from red blood cells into the tissues, where it is utilized for cellular metabolism. Conversely, carbon dioxide, a byproduct of this metabolic process, diffuses from the tissues into the blood to be transported back to the lungs for exhalation. This gas exchange process is vital for maintaining homeostasis and ensuring that tissues receive the oxygen necessary for survival while removing carbon dioxide efficiently.

Other systems, like the venous and arterial systems, play crucial roles in transporting blood but are not directly involved in the exchange of gases. The pulmonary system is primarily responsible for gas exchange in the lungs, not at the tissue level. Therefore, the capillary system is the correct answer, as it is specifically designed for direct gas exchange between blood and tissues.