netter84

tlechanics of Respiration: Surface Forces

RESPIRATORY PHYSIOLOGY

Pressure (cm HjO)

alveoli is thc same. A greater pressure is required to keep smali alveolus open. Smali alveokis tends to empty mto larger one

smali akeolus. Pressure distending both alveoli is approximately the same. Alveoli are stabilized, and the tendency lor smali alveolus to empty into larger one is reduced

Figurę 5.10 Surface Forces in the Lung_

"V aKeoli are coated with a thin film of surfactant <li|łoprotein pro -<ed by type 2 alveolar cellsi. Surfactant reduces the surface ten-- ihat exists ai the air-alveolar inlerface. This has several eftects, iuding a decrease in elastic recoil of the lung, an inerease in lung mpliance, and a decreast* in Ihe work required to inflate the lung

during inspiration. Surfactants' effect on surface tension is greater in smali alveoli compared with largo alvcołl Tliis lends to stabilize the alveoli and thereby equali/e alveolar pressures throughout the lung.

99