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Unformatted text preview: Bio 20B April 17, 2007 Respiratory Systems (Gas Exchange) Mechanics of Breathing Diaphragm is the most important muscle o Bidirectional Flow (goes in and out the same way) Inter Pleural Space o Lungs are elastic so easy to distend Lungs adhere to chest wall o Space between lungs and chest wall is called Inter Pleural Space Negative pressure (suction or vacuum) to keep lungs inflated Chest wounds create a hole, which Increases pressure so lungs collapse Chest wall expands pneumothorax Gas Exchange in Mammal lungs (diagram in notebook) o Open pool system Air passes into alveoli and diffuses into the capillaries and takes the CO 2 from the capillaries and carries it out o Elasticity of the Lungs Few hydrogen bonds at surface (water can bond only with molecules below) versus many hydrogen bonds on alveolar wall = net upward force on alveolar wall (thin wall) Surfactin (spelling?) helps reduce surface tension allowing alveoli to expand and contract Avian (Bird) Respiration o Key Concepts about Bird Respiration Constant Lung Volume Airflow through lung is unidirectional Non-moving lung o Anatomy of Bird Lungs (Freeman Fig. 44.11a) From trachea, air goes into posterior air sacks (which expand and contract) and force air into the bird lung (parabbronchi) and then back into the anterior air sacks and then leaves the body Campbell Fig. 42.24 describes bird respiration Lungs (parabronchi) are connected to a series of air sacks Air sacks act like bellows to push air through lungs Alternate between inflation and deflation Inhalation occurs when air is moving into the air sacks and exhalation occurs when air first goes into the lungs and then again when the air is being pushed out of the body Bird has almost continuous flow of air through lungs, only the air sacks change volume o The amazing Parabronchi (Lungs) Parabronchi does not change volume The flow of air through the parabronchi is one way (unlike mammals) New air passes through the parabronchi with each inspiration and expiration High oxygen extraction efficiency because of cross current flow of air over blood vessels within parabronchi...
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