BPK 205 Lecture Notes - Lecture 25: Alveolar Cells, Functional Residual Capacity, Transpulmonary Pressure
Document Summary
Describe the function of surfactant on alveolar surface tension. Surfactant is secreted by type ii alveolar cells and lines the inside surface of alveoli. Surfactant functions: decrease surface tension inside the alveoli, preventing alveoli from collapse, making the alveoli easier to expand. Surfactant decreases the tension, thus decreasing the pressure and making alveoli easier to expand: causes fluid to stay together and bead up into a spherical shape. Surfactant and law of laplace: two bubbles have the same surface tension -> according to law of laplace, the pressure is greater in the smaller bubble, surfactant reduces surface tension. 2: surfactant reduces surface tension and inward pressure -> reduces the work to inflate alveoli, smaller alveoli have more surfactant, equalization of the pressure between large and small alveoli, air flow is equalized to all alveoli. Alveolar and intrapleural pressures at rest: pip -> will always be negative, transpulmonary pressure pushes lung tissue up against the chest/thoracic wall.