Lecture5 - Lecture #5 VII. Diffusion and Perfusion A....

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Lecture #5 08/07/2008 15:29:00 VII. Diffusion and Perfusion A. Diffusion: How does oxygen move into the blood? * All gases move across the alveolar wall by passive diffusion Depends on: 1. tissue thickness of the wall 2. surface area (want large surface area-more chance to cross membrane) 3. partial pressure of gases on each side of membrane  GRADIENTS (bigger  gradient=faster) *partial pressure= amount of gas 4. Diffusion constant:  Higher in athletic animals (cheetah)/ animals adapted to high altitudes  5. Type of gas: carbon dioxide diffuses 20 ×  faster than oxygen (figure 1) B. Balance of diffusion and Perfusion Diffusion: getting gases across alveolar membrane Perfusion: how much blood you have flowing past alveoli (figure 2.1 on handout) diffusion path alveoli RBC reaction with hemoglobin (Hb) O2+ Hb    HbO2 (fast)                                                         (0.20sec)  rate limiting step (figure 3+4)
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What happens at altitude? (figure 5) strategies at altitude o increase RBC (human adaptations; NOT born at altitude) o increase Hb o if born and raised at altitude  Diffusion capacity (figure 6+7) C. regional variation in blood flow to lungs Blood flow to lung is greatest at the  bottom of lung Decreases linearly as a group Get more uniform as you exercise (figure 8) Zone 1: alveolar pressure > pulmonary arterial pressure> venous pressure
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This note was uploaded on 07/23/2008 for the course BIO 131 taught by Professor Mostman during the Summer '08 term at UCSC.

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Lecture5 - Lecture #5 VII. Diffusion and Perfusion A....

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