The Mechanics of Ventilation in Human Lungs
Understanding Ventilation Basics
Ventilation is the mechanical process of moving air in and out of the lungs, commonly known as breathing. This process involves two main phases:
- Inspiration (breathing in)
- Expiration (breathing out)
Both phases rely on pressure differences between the atmosphere and the lungs, following the principle that air moves from areas of high pressure to areas of low pressure.
The Role of the Thoracic Cavity
The thoracic cavity houses our lungs and is surrounded by several key structures:
- Ribcage
- Intercostal muscles (external and internal)
- Diaphragm
- Pleural membranes (visceral and parietal)
Mechanics of Inspiration
During inspiration:
- The diaphragm contracts and flattens
- External intercostal muscles contract
- Ribs move upward and outward
- Thoracic cavity volume increases
- Lung volume increases
- Intrapulmonary pressure decreases below atmospheric pressure