BIOL 2P97 Lecture 9: Respiratory system: Part 1
2 Dec 2015
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Document Summary
Each cluster of alveoli is surrounded by elastic fibers and a network of. This image shows the very high capillary density in alveoli. The capillaries are almost like a thin-walled sheet surrounded each alveolus. This creates an enormous surface area, which facilitates the diffusion of respiratory gases (o2 and co2) In addition, the capillaries rest right up against the alveolar epithelium so that the distance these gases must diffuse between blood and alveolar airspace is minimized. Blood flow in the pulmonary circulation must exactly match that in the systemic circulation, since it is a closed system. Also, pulmonary blood flow is virtually always matched with pulmonary ventilation rate & depth. The body increases blood flow coincident with increased metabolic rates. So it is appropriate to increase ventilation rate as well to facilitate respiratory gas exchange under such conditions. Pulmonary flow = systemic flow ~ ventilation rate.
