AP BIOLOGY

Detailed explanation-1: -Bronchioles end in tiny air sacs called alveoli, where the exchange of oxygen and carbon dioxide actually takes place. Each person has hundreds of millions of alveoli in their lungs.

Detailed explanation-2: -The walls of the alveoli share a membrane with the capillaries. That’s how close they are. This lets oxygen and carbon dioxide diffuse, or move freely, between the respiratory system and the bloodstream.

Detailed explanation-3: -Oxygen breathed in from the air passes through the alveoli and into the blood and travels to the tissues throughout the body. Carbon dioxide travels in the blood from the body’s tissues and passes through the alveoli to be breathed out.

Detailed explanation-4: -The carbon dioxide diffuses out of the red blood cells, through the capillary walls, and into the alveolar spaces f exhaled.