Lecture 7 - Mechanics of Ventilation

Lecture 7 - Mechanics of Ventilation - Lecture 7: Mechanics...

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Lecture 7: Mechanics of Ventilation *compliance = flexibility Comparison of cardiac and respiratory cycles o Differences average duration: respiratory cycle 5 secs o delivers air: 5 L/min cardiac cycle 300-400 msec o delivers blood: 5 L/min ventilation profusion matching : respiratory and cardiac cycle delivers the same volume of blood/air Cardiac systole: (ejection of flow) vs Respiration inspiration (intake of ambient air) Cardiac diastole: (intake of flow) vs Respiration expiration (exhaustion of air) o Similarities Both systems need to expend energy to keep fluid and air flowing Both systems experience central control Pulmonary Mechanics and Ventilation Overview o Recoil forces in lungs and thorax purpose of ventilation : to provide ambient air to alveolar membranes; this system is based upon ecoil elastic forces in lungs and thorax Lung Parenchyma : general mass that makes up alveoli, their walls, and extracellular system that supports the alveoli thorax cavities also has elastic properties that recoil and must move with respiratory cycles o pleural space and pressure (intra)pleural space : between lung parenchyma and inner lining of thoracic cavity there is pressure inside this space that changes cyclicly during respiratory cycle pleural space isn’t actual space—it’s a virtual space o surface tension and surfactant alveolar type 2 cells in parenchyma produce sufactant: “surface” + “active” + “agent” = surf-act-ant lipid-like produced by : type 2 alveolar cells function : reduce surface tension—one of the forces that the longs have to overcome in expanding during inspiration o Pneumothorax and lung re-expansion Slide 1 Slide 2
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Elastic Recoils of Lungs and Thorax : o intrapleural space : everything between outside of lungs and the thorax formed by 2 epithelial membrane: parietal pleura: innermost epithelial lining of thorax o has a circulatory system made microvessels that is “weepy” –plasma seep out of these capillaries easily visceral pleura: outermost epithelial layer of lung parenchyma o location of pulmonary lympatic circulation location: 2 circulatory systems next to each other and between them is the pleural space o Volume of intrapleural space : 10-12 mL (or aka pleural fluid) can measure fluid in this space letting us know the volume volume of fluid inside pleural space at any time is the function of rate of production of exudates from the parietal pleural capillaries and rate of removal of exudates by visceral pleural lympathic muscles o equilibrium of these 2 can be disrupted by disease, accident and unknown means o exudates: cells or fluid leaving blood vessels or organ o distance b/n parietal pleural and visceral pleura : 5-30 micrometers o purpose of this slide: to show us net direction of elastic forces during respiratory cycle in conjuction with effect of pleural pressure and the fluid that
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Lecture 7 - Mechanics of Ventilation - Lecture 7: Mechanics...

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