PHYSIOL 1 Lecture Notes - Lecture 32: Surface Tension, Bronchoconstriction, Obstructive Lung Disease
Document Summary
Air moves between the environment and the alveoli via bulk flow, a process known as ventilation. Flow= (pressure of alv-pressure of atm)/r of airways. If the pressure of alv is less than the pressure of atm, air flows in (inspiration) If the pressure of alv is greater than pressure of atm, air flows out (expiration) We change alv pressure by boyles law. Boyles law: for a given # of gas molecules in a container: To change pressure in alv, the volume of the lungs must change. Change in lung size brought by change in forces acting upon lungs. Pip is always negative because lungs recoil inward and chest wall recoils outward. Thus ptp (transpulmonary pressure) is always positive, this provides the force that expands the lungs. Elastic recoil is force that shrinks the lung. Balance between elastic recoil and ptp will determine lung size. If negative pip is lost then ptp drops to 0.
