When gases are exchanged at the air sacs in the lungs, the process that primarily takes place is diffusion. Diffusion is the movement of molecules from an area of high concentration to an area of low concentration. In the context of gas exchange in the lungs, oxygen moves from the alveoli (air sacs) into the blood where the concentration of oxygen is lower, while carbon dioxide moves from the blood into the alveoli where its concentration is lower.
Here's a step-by-step breakdown of what happens during gas exchange at the air sacs:
1. When you inhale, oxygen-rich air enters the lungs and reaches the alveoli.
2. Oxygen diffuses across the thin walls of the alveoli and into the surrounding capillaries (tiny blood vessels).
3. The oxygen binds to hemoglobin in red blood cells and is transported to cells throughout the body for cellular respiration.
4. At the same time, carbon dioxide, a waste product of cellular respiration, diffuses from the capillaries into the alveoli.
5. Carbon dioxide is then exhaled out of the lungs when you breathe out.
While osmosis is the movement of water molecules across a semi-permeable membrane, and phagocytosis is a process by which cells engulf and digest solid particles, these processes are not primarily involved in gas exchange at the air sacs.
In summary, the exchange of gases at the air sacs mainly involves the process of diffusion, where oxygen and carbon dioxide move across the respiratory membrane to facilitate the exchange of gases between the lungs and the blood.
