Mechanism of breathing

Mechanism of breathing - Mechanism of breathing In order to...

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Mechanism of breathing In order to grasp the way in which we breathe we have to grasp the following facts: Each lung is surrounded by a pleural cavity or sac, except where the plumbing joins it to the rest of the body, rather like a hand in a boxing glove. The glove has an outer and inner surface, separated by a layer of padding. The pleura, similarly, has two surfaces, but the padding is replaced by a thin layer of fluid. Each lung is enclosed in a cage bounded below by the diaphragm and at the sides by the chest wall and the mediastinum (technical term for the bit around the heart). It is not usually appreciated that the lung extends so high into the neck. A syringe inserted above a clavicle may pierce the lung. Breathing works by making the cage bigger: the pleural layers slide over each other and the pressure in the lung is decreased, so air is sucked in. Breathing out does the reverse, the cage collapses and air is expelled. The main component acting here is the diaphragm. This is a layer of muscle which is convex above, domed, and squashed in the centre by the heart. When it contracts it flattens and increases the space above it. When it relaxes the abdominal contents push it up again. The proportion of breathing which is diaphragmatic varies from person to person. For
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This note was uploaded on 11/08/2011 for the course BIOLOGY BSC1086L taught by Professor Leostouder during the Fall '10 term at Broward College.

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Mechanism of breathing - Mechanism of breathing In order to...

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