PNB 2265 Lecture Notes - Lecture 18: Latissimus Dorsi Muscle, Accessory Muscle, Abdominal Wall
1 Mar 2017
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Document Summary
Transport of respiratory gases in the blood. Air moves in and out of lungs by bulk flow: f= p/r. Pressures: atmospheric pressure (patm)=0, alveolar pressure (palv) Equalizes between breaths: intrapleural pressure (pip, transpulmonary pressure (ptp)=palv-pip. Holds lungs open: chest wall (pcw)=pip-patm, changing palv-patm, causes air flow, understand what would happen if you had a pneumothorax, or a hole in the chest wall. Alveolar (palv) pressure, aka intrapulmonary pressure: pressure within alveoli, equalizes with atmospheric (between breaths) Intrapleural pressure (pip: pressure in the intrapleural fluid, always at least 4 mmhg less than alveolar pressure. Mechanism of negative pressure in the intrapleural space. Two forces act to pull the lungs (visceral pleura) away from the thorax wall (parietal pleura: recoil due to elasticity of lungs, surface tension of alveolar fluid. Transpulmonary pressure: opposing force that keeps lungs open: surface tension created by pleural fluid in the pleural cavity, glues visceral pleura (and lungs) to parietal pleura.
