Pulmonary Physiology Lange Physiology By Michael G Levitzky
Chapter 15: Pulmonary mechanics Introduction: The breathing cycle consists of inspiration (insp) and expiration (exp). Lung ventilation is the flow of air into and out of the lungs. The function of the lungs is to supply the body with oxygen and expel carbon dioxide and other waste products. The lungs consist of a number of structural components: 1. The trachea 2. The two lung sacs 3. The respiratory bronchioles 4. The respiratory bronchioles 5. The alveoli 6. The terminal bronchioles 7. The bronchioles 8. The air sacs 9. The connective tissues (viscera) Pulmonary Mechanics The word mechanics means the study of the relationship between forces and motion. All the forces involved in the respiration are transmitted to and from the lungs by the thoracic (chest) cage, the respiratory (breathing) muscles, and the lungs. The lungs are organs that absorb oxygen and expel carbon dioxide, the gas exhaled through the nose and mouth. They are therefore called the "gas-exchanging organs." The lungs have an important gas exchange function. Because oxygen cannot diffuse from the alveolar gas into the blood, pulmonary gas exchange is accomplished by diffusion from the alveolar gas to the alveolar capillaries. Because carbon dioxide cannot diffuse from the blood into the alveolar gas, pulmonary gas exchange is accomplished by diffusion of carbon dioxide from the alveolar gas to the alveolar capillaries. The process of gas exchange requires a certain amount of time, or a certain amount of time. It must take place as the pulmonary gas moves from the alveolar gas to the alveolar capillaries. This diffusion process is called alveolar ventilation. The lungs contain three compartments: 1. The gas-exchanging alveoli 2. The conducting airways 3. The respiratory bronchioles Respiratory Mechanics The Lung Ventilation The air moving into the lungs is divided into two chambers: 1. The gas-exchanging alveoli 2. The conducting airways The Air Moving Into the Lungs: The external nose and mouth contain a constant stream of air that originates in the nose. This continuous air movement has three components: 1. Expiratory air, which comes out of the nose, mouth, and sinuses 2. Inspiratory air, which moves into the lungs 3. Pneumatic, or pressure, waves, which move into and out of the
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