ANP 1105 Lecture : Chapter 22 the respiratory system physiology.doc

• School: University of Ottawa
• Department: Anatomy and Physiology
• Course: ANP 1105
• Professor: Jacqueline Carnegie

Document Summary

Breathing or pulmonary ventilation consists of inspiration when air flows into the lungs and expiration when gases exit the lungs. Respiratory pressures are always described relative to atmospheric pressure. Patm is the pressure exerted by gases surrounding the body. Pressure rises and falls with the phases of breathing but always equalizes with atmospheric pressure eventually. 2 forces act to pull the lungs (visceral pleura) away from the thorax wall (parietal pleura) to cause the lung to collapse: the lung"s natural tendency to recoil. Lungs always assume the smallest size possible due to their elasticity: the surface tension of the alveolar fluid. Molecules of the fluid lining the alveoli attract each other and produces surface tension that constantly acts to draw the alveoli to their smallest possible dimension. These lung-collapsing forces are opposed by the natural elasticity of the chest wall and tends to pull the thorax outward and enlarge the lungs.