2. Surfactant & Compliance Flashcards
What cells make up the alveolar wall ?
Type I cells- permits gas exchange Type II cells- secretes surfactant
What is the function of surfactant ?
Reduces surface tension on alveolar cell surface membrane, thus reducing tendency for alveoli to collapse reduces lungs tendency to recoil makes work of breathing easier increases lung compliance
What is surface tension ?
The attraction that occurs between water molecules that occurs whenever there is an air-water interface and refers to the attraction between water molecules
When is surfactant more effective ?
More effective in small alveoli than larger alveoli as surfactant molecules come closer together and are therefore more concentrated
What is the law of LaPlace ?
pressure required to keep alveoli open P=2T/r
What alveoli has the greatest pressure ?
Smallest alveoli
What force needs to be overcome during inspiration ?
Inward force caused by the elasticity of the lungs - they are stretched slightly open even at the end of a relaxed expiration - natural tendency to recoil (contract inwards)
When is surfactant produced ?
starts at 25 weeks gestation and finishes 36 weeks gestation
What is surfactant production stimulated by ?
Thyroid hormones and cortisol
What do premature babies suffer from ?
Infant Respiratory Distress syndrome (IRDS)
What is compliance ?
Change in volume relative to change in pressure
What does high compliance mean ?
Large increase in lung volume for small decrease in ip pressure
What does low compliance mean ?
Small increase in lung volume for large decrease in ip pressure
What is fibrosis ?
Inert fibrous tissue means effort of inspiration increasesDecreases compliance of the lungs
