Mechanism of
respiration
At rest
- Chest wall tends to expand , lung tends to recoil
- Opposing are balanced ; therefore ,negative intra-pleural pressure is developd
At inspiration
- Active process
- Main muscle – diaphragam
During quit inspiration
- Chest wall expands
- Lung begins to expand because visceral pleura is in contact with parietal pleura
- Expansion of lung leads to increased elastic recoil
- Intra plural pressure becomes more negative ( - 6 mmHg )
- It’s transmitted to alveoli ( - 1 to – 1.5 mmHg )
- Pressure gradient is created between atmosphere and alveoli
- Air flows in , until the pressure equalize
At expiration
- Passive process
- Maucle stop contracting during quiet expiration
- Thorax and lung come back to their orginal positions due to elastic recoil forces
- Alveolar pressure becomes (+) positive relative to the atmosphere
- Air flows out until the pressure euqlize
- Negative itrapleural pressure return to previous valuve
- But does not become positive
At forced expiration
- It is an active process
- itra- pleural pressure can become positive
Labels: Revision, RS, RS Revision