Tutorial: Quiet Breathing.

At Rest:

(After expiration ends and before inspiration begins.)

1. With the respiratory muscles at rest, the elastic recoil of the lung (Palv-Ppl=+5) and of the chest wall (Ppl-Pbs=-5) are equal but opposite.

2. Pleural pressure is subatmospheric (note the purple color in the pleural space).

3. Pressure along the tracheobronchial tree and in the alveoli is equal to atmospheric pressure. There is no air flow.

4. Air will only flow only from an area of higher pressure to one of lower pressure. Since alveolar pressure equals atmospheric pressure there is no air flow.

Please click the "next" button to continue.

Last modified, January 22, 1996
Johns Hopkins School of Medicine, 1994
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