How does air from the atmosphere get into lungs?

The process of air getting into the lungs is called inhalation or inspiration. Here's a step-by-step explanation of how air from the atmosphere gets into the lungs:

1. Diaphragm and Intercostal Muscles:

- Inhalation begins with the contraction of the diaphragm, a large muscle located at the base of the ribcage, and the intercostal muscles between the ribs.

2. Ribcage Expansion:

- The diaphragm's contraction causes it to move downward and the intercostal muscles pull the ribs upward and outward. This movement expands the ribcage and increases the volume of the chest cavity.

3. Lung Expansion:

- As the chest cavity expands, the lungs, which are elastic structures, also expand. This creates a decrease in air pressure within the lungs compared to the atmospheric pressure outside.

4. Air Pressure Difference:

- Due to the pressure difference, air from the atmosphere, which has a higher pressure, rushes into the lungs through the nose or mouth and into the windpipe (trachea).

5. Trachea and Bronchi:

- The trachea branches into two bronchi, one leading to each lung. The bronchi further divide into smaller branches called bronchioles.

6. Alveoli:

- The bronchioles end in tiny air sacs called alveoli. The alveoli are where gas exchange occurs, with oxygen from the inhaled air diffusing into the bloodstream and carbon dioxide from the bloodstream diffusing into the alveoli.

7. Exhalation:

- After inhalation, the diaphragm and intercostal muscles relax, causing the chest cavity to decrease in volume, which pushes the air out of the lungs and back into the atmosphere through the same pathway it entered.

This process of inhalation and exhalation occurs continuously, allowing for the continuous exchange of oxygen and carbon dioxide, which is essential for sustaining life.