1. Oxygenated blood is necessary for proper bodily functions. If there isn't enough oxygen in a person's blood they can become light headed, disoriented, and feel extremely tired. How does the oxygen enters the blood?

The oxygen enters the bloodstream from the alveoli, tiny sacs in the lungs where gas exchange takes place.

The transfer of oxygen into the blood is through simple diffusion. The oxygen molecules move, by diffusion, out of the capillaries and into the body cells.

The oxygen enters the bloodstream from the alveoli, tiny sacs in the lungs where gas exchange takes place. The transfer of oxygen into the blood is through simple diffusion ... The oxygen molecules move, by diffusion, out of the capillaries and into the body cells.