4.4 Flashcards
What is meant by compliance of the lungs?
The extent to which the lungs will expand for each unit increase in transpulmonary pressure
What two factors determine lung compliance?
- Elastic forces of the lung
- Elastic forces caused by surface tension
What is surface tension?
The tension of a surface film of a liquid, caused by the attraction of the particles in this surface layer.
Use the law of laplace to explain why a smaller alveolus is harder to breathe through than a larger one
LaPlace: P=2T/r, meaning alveolar pressure is inversely proportional to radius of an alveolus. Since a smaller alveolus implies a smaller radius, there must be a higher alveolar pressure to be overcome in order to breathe. (Assuming surface tension is identical)
Why do the lungs expand when the thoracic wall increases in size?
Because the parietal pleura is connected to the chest wall via the endothoracic fascia, and the visceral pleura (which is connected to the lungs) is adhered to the parietal pleura due to the subatmospheric pressure within the pleural cavity.
Expiratory/Inspiratory reserve volume
The extra volume of air that can be expired/inspired with max effort after a regular expiration/inspiration
Tidal volume
The amount of air that moves in our out of the lungs with each respiratory cycle
Vital capacity
Total amount of air that can be maximally exhaled after a maximal inhalation
Functional residual capacity
Amount of air remaining in lungs after normal expiration
