Oxygen diffuses through the capillary wall, into the tissue fluid and the cells. Carbon dioxide diffuses from the cells into the tissue fluid, then across the capillary walls into the blood plasma . Glucose diffuses from the blood plasma, across the capillary walls to the tissue fluid, and then to the cells.

What flows in capillaries?

Arterioles connect with even smaller blood vessels called capillaries. Through the thin walls of the capillaries, oxygen and nutrients pass from blood into tissues, and waste products pass from tissues into blood. From the capillaries, blood passes into venules, then into veins to return to the heart.

What diffuses from the capillaries into cells for respiration?

Red blood cells carry the oxygen into the capillaries of the tissues of the body. Oxygen diffuses into the cells of the tissues, while carbon dioxide diffuses out of the cells of the tissues and into the bloodstream.