Chapter 17 Notes - Mechanics of Breathing

Chapter 17 Notes - Mechanics of Breathing - Exchange of...

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- O2 is brought into the lungs and distributed to the tissues. CO2 is waste produced by metabolism Homeostatic regulation of body pH – we can selectively retain or excrete carbon dioxide, thereby regulating the body’s pH (higher CO2 correlates with a lower body pH) We know that fluids move from areas of higher to lower pressure (air is a fluid, so it follows this general path) - A muscular pump creates these pressure gradients. - Resistance to air flow is influenced primarily by the diameter of the tubes through which the air is flowing. Air is compressible . Ventilation – exchange of air between the atmosphere and the lungs (a general term) Inspiration and expiration – movement of air into and out of the lungs. Airways direct air from the atmosphere into the lungs in the alveoli, oxygen and carbon dioxide diffuse accordingly so oxygen diffuses into the blood, and carbon dioxide diffuses into the alveoli to be exhaled. Pleural sacs in the thorax enclose the lungs. - Pleural membranes contain layers of elastic connective tissues and numerous capillaries. - Pleural fluid holds the pleural membrane intact, and provides a slippery surface for opposing membranes to slide across one another as the lungs move. Similar analogy – two sheets of glass being held together with a thin layer of water in between: they can slide back and forth across each other, but cannot be pulled apart due to cohesion of the water molecules. Pharynx – common passageway for lungs and food Larynx – air flows in here first, then through the trachea (called the windpipe) - Contains vocal cords: connective tissue bands that tighten to create sound when air moves past them. - Extends into a pair of primary bronchi (one bronchus per lung), into more bronchi, then into bronchioles - As individual airways get smaller, their numbers increase total cross-sectional area increases with each division of the airways. (for optimal surface area-volume ratio…seen in many systems in the body) Alveoli – primary sites of gas exchange - Type II alveolar cells – create surfactant (aid lungs in expanding while breathing): also responsible for transporting solutes (followed by water) out of the alveolar air space. - Surfactant decreases surface tension of the alveolar fluid and decreases resistance of the lung to stretch. -
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Chapter 17 Notes - Mechanics of Breathing - Exchange of...

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