HHP 3500 Lecture Notes - Lecture 35: External Intercostal Muscles, Intrapleural Pressure, Transpulmonary Pressure
2 Nov 2016
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Document Summary
Ventilation and lung mechanics- what is breathing: pulmonary ventilation- air movement between the environment and alveoli(lungs) Transport involves bulk flow, so f = pressure/resistance. Ventilation is a tidal flow system, meaning air flows in and out with the same route. Pressure regulated by difference between air and alveoli; if palv< To move air in and out of lungs, we must cyclically change p alv. We do this by changing volume of lungs. As volume of lungs decreases, pressure of lungs increases, encouraging expiration. Then as volume of lungs increases, pressure of lungs decreases, encouraging inspiration. Active process driven by contraction of diaphragm (activated by phrenic nerves) and external intercostal muscles. When diaphragm contracts it flattens into abdomen. Expansion of thorax causes intrapleural pressure to become more negative, increasing transpulmonary pressure, which causes lungs to expand. The increased volume causes decreased pressured, so air flows into alveoli: expiration.
