Inspiration:
Inspiration is the process by which air is taken into the lungs. Under normal (quiet) breathing conditions, inspiration is an active process.
Process of inspiration:
• The diaphragm contracts and moves downward, becoming flat.
• The external intercostal muscles contract, lifting the ribs upward and outward.
• As a result, the volume of the thoracic cavity increases.
• Increase in thoracic volume causes a decrease in intrapulmonary (alveolar) pressure.
• The pressure inside the lungs becomes lower than atmospheric pressure.
• Due to this pressure difference, air rushes into the lungs from the atmosphere.
Role of muscles:
During normal inspiration, only the diaphragm and external intercostal muscles are involved. No extra muscles are required under resting conditions.
Conclusion:
Thus, inspiration under normal conditions occurs due to contraction of the diaphragm and intercostal muscles, leading to an increase in thoracic volume and entry of air into the lungs.
| List I | List II | ||
| A | Expiratory capacity | I | Expiratory reserve volume + Tidal volume + Inspiratory reserve volume |
| B | Functional residual capacity | II | Tidal volume + Expiratory reserve volume |
| C | Vital capacity | III | Tidal volume + Inspiratory reserve volume |
| D | Inspiratory capacity | IV | Expiratory reserve volume + Residual volume |