BIO 11 Lecture Notes - Lecture 9: Surface Tension, Asthma, Intercostal Muscle
3 Sep 2020
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Expiration: air moves out of the lungs. Pressure: air moving from high pressure to low pressure. Pressure in the lungs changes because the volume of the lungs keeps changing. Volume: the lungs expand to increase/decrease the volume. Need it in order for gases to move. Atmospheric: pressure of the air in the atmosphere around us. Air is always pushing down on us. At sea level 760mm hg = 1 atm. Intrapulmonary: pressure of the air inside of the lungs. Pressure outside of the lung always has to be less than the pressure inside the lungs. Transpulmonary: the difference in pressure between intrapulmonary and intrapleural. Inspiratory muscles contract: diaphragm pulls down to create space for air. Intercostal muscles contract and rib cage expands enlarging the thoracic cavity. Pressure in the lungs goes down, air goes in. Intercostal muscles relax decreasing the thoracic cavity. Pressure in the lungs goes up air goes out.
