Alveoli

Tiny air sacs at the end of the bronchioles in the lungs.

Small balloon-like air sacs in the lungs where oxygen and carbon dioxide are exchanged.

The microscopic air sacs in the lungs through whose walls the exchange of carbon dioxide and oxygen occurs.

The smallest airways in the lungs that contain the membranes through which gases are exchanged with the blood.

Cell structures in the lungs responsible for O2/CO2 exchange.

Hollow, sphere-shaped cells of the lung that function to exchange oxygen and carbon dioxide.

Microscopic air sacs within the lungs and the site of gas “exchange. The alveoli are clustered together like grapes at the end of a bronchiole (small air tube). Each alveolus is made of connective tissue surrounded by very small blood vessels called capillaries. Air that is inhaled travels through the successively finer air passageways of the respiratory system to the alveoli.

Microscopic air sacs within the lungs and the site of gas exchange. The alveoli are clustered together like grapes at the end of a bronchiole (small air tube). Each alveolus is made of connective tissue surrounded by very small blood vessels called capillaries. Air that is inhaled travels through the successively finer air passageways of the respiratory system to the alveoli. The thin wall of the alveoli absorb the oxygen molecules from the air, which then pass through the capillary walls into the bloodstream to oxygenate the blood (which then circulates to body tissues). At the same time, the waste product carbon dioxide passes from the blood through the walls of the capillaries and into the alveoli and is expelled from the lungs in exhaled air. The exchange takes place at this cellular level because oxygen in the alveolus is at higher pressure than in the capillaries, and carbon dioxide is at higher pressure in the capillaries than in the alveolus. This gas exchange is called true respiration.