How do glucose and oxygen get into the blood to be used for respiration?

When we breathe we inhale oxygen from the air into our lungs. The alveoli are tiny air sacs in the lung where oxygen diffuses into the blood via small blood vessels, known as capillaries. The blood in these capillaries has a low concentration of oxygen which allows oxygen in the alveoli to diffuse down the concentration gradient and into the blood. When we eat food, it is broken down by enzymes, such as amylase, in the digestive system. Glucose is formed by the breakdown of carbohydrates in the small intestine. Glucose is then absorbed into the blood from the small intestine via the villi by active transport. Glucose and oxygen travel in the bloodstream and are taken up into cells. Respiration takes place in the mitochondria, producing energy.