12 November 2008 Respiratory Physiology Mostly white board diagrams in class today covering: 5L blood over tennis court = huge surface area for gas exchange. Ventilation = movement of air by bulk flow in response to pressure gradients (Boyle’s law) (Atmospheric and alveolar pressures) Gas exchange by diffusion. Tidal Inspiration is active (requires muscle contraction of diaphragm and intercostal muscles.) Tidal expiration is passive (elastic recoil of lung tissue.) Compliance (opposite of stiffness) is influence by surface tension in alveoli (governed by Law of Laplace) and altered by surfactant which reduces surface tension and increases compliance.

Figure Type II pneumocytes secrete surfactant. Gas exchange by diffusion based on gradients.

Figure Pneumothorax (unilateral due to each lung having its own compartment. Greg R. and the story of spontaneous pneumothorax Visceral pleura and parietal pleura separated by fluid-filled pleural cavity which allows lung and chest wall to slide relative to each other but remain adhered unless air enters the pleural cavity (which leads to collapse of the lung and outward expansion of chest wall on that side.)

Figure Who cares? Respiratory Distress Syndrome of the Newborn

Table 13.04

Figure 13.19

V = V T x f V A = (V T – V DS ) x f Anatomic dead space = air remaining in conducting zone (typically 150 ml.) What if Tidal Volume is 150 ml? Matching blood flow (Q) to ventilation (V) by pulmonary arterioles that constrict in response to low O 2 and dilate in response to hi O 2. Thus, poorly ventilated regions of the lung will receive less blood flow.

Table 13.05