The alveoli, which are tiny air sacs in the lungs, are adapted to their function in several ways. Here are the key adaptations:
- Large surface area: The alveoli provide a very large surface area for efficient gas exchange. In the lungs of a human adult, there are approximately 300 million alveoli, which results in a total area of about 90 square meters, nearly as large as a basketball pitch.
- Thin and flat epithelium: The walls of the alveoli are composed of a layer of thin and flat epithelial cells. This thin barrier allows for rapid diffusion of gases, making the exchange of oxygen and carbon dioxide between the air in the alveoli and the blood in the adjacent capillaries efficient.
- Moist lining: The internal surface of the alveoli is lined with mucus, which helps in the rapid diffusion of gases. The moisture in the alveoli aids in the dissolution of oxygen from the inhaled air and facilitates the exchange of gases.
- Rich blood supply: The alveoli have a rich supply of blood capillaries, which allows for rapid gaseous exchange. Oxygen diffuses from the alveoli into the adjacent capillaries, where it binds with hemoglobin in red blood cells and is transported to all parts of the body. Carbon dioxide, on the other hand, diffuses from the capillaries into the alveoli to be eliminated during exhalation.
These adaptations of the alveoli ensure efficient gas exchange, allowing oxygen to enter the bloodstream and carbon dioxide to be removed from the body.