The air then goes through the series of branches in your lungs, through the bronchi and the bronchioles. The air finally ends up in the 600 million alveoli. As these millions of alveoli fill up with air, the lungs get bigger. It's the alveoli that allow oxygen from the air to pass into your blood. All the cells in the body need oxygen every minute of the day.
Oxygen passes through the walls of each alveolus into the tiny capillaries that surround it.
The oxygen enters the blood in the tiny capillaries, hitching a ride on red blood cells and traveling through layers of blood veseels to the heart . For specific medical advice, diagnoses, and treatment, consult your doctor.