PHGY 210 Lecture Notes - Lecture 13: Surface Tension, Intrapleural Pressure, Smooth Muscle Tissue
14 May 2012
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Document Summary
Review of compliance: dynamics of a breath. From a mechanical point of view, the respiratory system may be regarded as a pump with elastic, flow-resistive and inertial properties (figure 40). Frc and ppl is negative due to the opposite forces acting on the lungs and chest wall. During inspiration, the diaphragm contracts and the chest wall is pulled open. This creates a more negative ppl that causes expansion of the lungs (figure 41). see pictures in slide. As the lungs are pulled further away from their resting position (which is below rv), As the volume of the lungs is increased, gas in the lungs is decompressed. The pressure in the alveoli (palv) drops below atmospheric pressure. The created negative pressure gradient between the alveoli and atmosphere generates air flow to the lungs. As inspiration proceeds, the lungs are filling up with air, and the pressure gradient and the air flow gradually decrease.
