The alveoli play a crucial role in the process of respiration by facilitating the exchange of gases, specifically oxygen and carbon dioxide, between the lungs and the bloodstream.
Here's how the alveoli work in respiration:
.jpeg)
1. Structure of Alveoli: Alveoli are tiny, grape-like air sacs located at the ends of the respiratory bronchioles in the lungs. They have thin walls that are surrounded by a dense network of capillaries. The combined surface area of the alveoli provides a large area for gas exchange to occur.
2. Inhalation: During inhalation, the diaphragm contracts and moves downward, and the intercostal muscles between the ribs contract, causing the ribcage to expand. This expansion increases the volume of the chest cavity, leading to a decrease in air pressure within the lungs. As a result, air from the atmosphere moves into the lungs through the airways.
3. Gas Exchange: Within the alveoli, oxygen from the inhaled air diffuses across the thin walls of the alveoli and into the surrounding capillaries. This diffusion is driven by the difference in oxygen concentration between the alveoli and the blood in the capillaries. At the same time, carbon dioxide, a waste product generated by cells, diffuses from the capillaries into the alveoli.
4. Oxygen Transport: Oxygen binds to hemoglobin molecules within red blood cells, forming oxyhemoglobin. Oxygen-rich blood then flows from the lungs back to the heart and is pumped throughout the body, delivering oxygen to tissues and cells.
5. Carbon Dioxide Removal: Carbon dioxide produced by cellular respiration in the body tissues is transported by red blood cells back to the lungs. In the alveoli, carbon dioxide diffuses across the alveolar walls and is exhaled out of the body during exhalation.
6. Exhalation: During exhalation, the diaphragm and intercostal muscles relax, causing the ribcage to move inward and the chest cavity to decrease in volume. This decrease in volume increases the air pressure within the lungs, forcing air containing carbon dioxide out of the lungs and into the atmosphere.
The continuous process of inhalation and exhalation allows for the exchange of gases between the alveoli and the bloodstream, ensuring the supply of oxygen to the body's tissues and the removal of carbon dioxide. This gas exchange is vital for maintaining cellular respiration and providing the energy required for various bodily functions.
