What Happens Between the Alveoli and the Capillaries?
When the body works harder, it needs more oxygen. Air enters the lungs and moves from larger to smaller passages and finally to small sacs which resemble grapes on the end of a stem, called alveoli. Capillaries (tiny blood vessels) pick up oxygen as it enters the alveoli and waste products like carbon dioxide pass into the alveoli and are exhaled.