How is most oxygen transported to the blood?

Most oxygen is transported to the blood through the process of diffusion. Diffusion is the movement of molecules from an area of high concentration to an area of low concentration. In the case of oxygen, it is transported from the lungs, where the concentration of oxygen is high, to the bloodstream, where the concentration of oxygen is low. The diffusion of oxygen into the bloodstream occurs through the walls of the alveoli, which are small air sacs in the lungs. The alveoli are lined with capillaries, which are tiny blood vessels. The walls of the capillaries are very thin, allowing for the easy diffusion of oxygen from the alveoli into the blood.