Oxygen is released into body cells at the level of the capillaries, the smallest blood vessels in the circulatory system. The primary vessel type involved is the capillary, which connects arterioles (small arteries) to venules (small veins) and forms dense networks within tissues. Here's a concise breakdown:
- Where it happens: In the capillary walls, through the thin endothelial lining.
- How it happens: Oxygen bound to hemoglobin in red blood cells diffuses across the capillary endothelium and into surrounding tissue cells; simultaneously, carbon dioxide and other waste products diffuse from cells into the capillaries to be carried away.
- Why capillaries: They have the narrow diameters and extremely thin walls (often just a single endothelial cell thick) that maximize surface area and the gradient for efficient gas exchange.
- Related vessels: Arterioles deliver oxygenated blood to capillaries, and venules carry deoxygenated blood away from tissues toward veins, completing the systemic circulation.
If you’d like, I can tailor this to a specific tissue (e.g., muscle, brain) or explain the cellular mechanism of diffusion across the capillary wall.
