PowerPoint Presentation

Alveoli and Gas ExchangeThe Terminal End of the Breathing Tube

Inside the LungAfter oxygen passes into the lungs through the bronchial tubes, it moves into tiny sacs called alveoliAlveoli are spongy, air filled sacs that are surrounded by capillariesThe basic function of the alveoli is gas exchange

Alveoli and Capillaries

AlveoliThe inhaled oxygen moves into the alveoli. The walls of the alveoli are just two cells thick.The thin walls allow the oxygen to diffuse out of the alveoli and into the capillaries where it is taken up by red blood cellsAs the oxygen moves into the red cells, carbon dioxide (a waste product), is released from the cells The CO2 moves into the alveoli and it is exhaled from the lungs

AlveoliThere are about 400 to 500 million alveoli in the adult lungBecause there are so many alveoli, their surface area is very large This provides a large area for gas exchange to occur

Gas Exchange