Alveoli are tiny, balloon-shaped air sacs located at the end of the bronchioles (small branches of the air tubes in your lungs). They are the primary sites of gas exchange in the lungs.
Function of Alveoli
The alveoli's main function is to facilitate the exchange of oxygen and carbon dioxide between the air and your bloodstream. Oxygen from the air you inhale passes into the alveoli and then diffuses across the thin alveolar walls into the capillaries (tiny blood vessels) surrounding them. Simultaneously, carbon dioxide, a waste product from your body's metabolism, diffuses from the capillaries into the alveoli and is exhaled.
- Inhaling: Oxygen-rich air enters the alveoli.
- Diffusion: Oxygen moves into the blood; carbon dioxide moves into the alveoli.
- Exhaling: Carbon dioxide-rich air leaves the alveoli.
Alveoli Structure
Alveoli are composed of thin, flat epithelial cells, creating a large surface area for efficient gas exchange. These cells are extremely delicate and easily damaged. The alveoli are surrounded by a dense network of capillaries, ensuring close proximity to the blood supply for efficient gas exchange.
Alveoli and Lung Diseases
Damage to the alveoli can lead to various lung diseases, including pneumonia. Pneumonia causes the alveoli to fill with fluid or pus, impairing their ability to transfer oxygen.
- Pneumonia: An infection causing alveoli to fill with fluid or pus.
- Emphysema: A condition where alveoli are destroyed, reducing lung capacity.
The Number of Alveoli
The human lung contains millions of alveoli, significantly increasing the total surface area available for gas exchange. The exact number varies between individuals, but a precise determination is challenging and depends on the methodology used.
