Pulmonary Function


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1 PULMONARY STRUCTURE AND FUNCTION I. Anatomy of the Respiratory System Respiratory system consists of nose, pharynx, larynx, trachea, bronchi, and lungs. Bronchi - primary, secondary, and tertiary bronchi ---> terminal and respiratory bronchioles ---> alveolar ducts ---> alveoli. With branching, supportive cartilage is gradually replaced by smooth muscle. Contraction and relaxation of this smooth muscle constricts or dilates the bronchioles --> major effects on airway resistance. The conducting airways lead inspired air to the alveoli. Volume of conducting airways = anatomic dead space (V D ) - 150 ml. Alveoli - small, thin walled sacs that have capillary beds in their walls; site of gas molecule (O 2 2 ) exchange between air and blood; there are millions of alveoli Respiratory membrane – alveolar-capillary membranes that separate the air molecules in the alveoli from the blood in the capillaries - average thickness is 0.6 micrometers. The respiratory membrane has a very large surface area – 70 square meters in the normal adult - size of tennis court. Lungs - contain conducting airways, alveoli, blood vessels, elastic tissue. II. Mechanics of Breathing Molecules move from areas of high pressure or concentration to areas of low pressure or concentration. Boyle's Law - the pressure of a gas is inversely proportional to its volume. The movement of air into and out of the lungs results from a pressure difference between the pulmonary air and the atmosphere.
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2 Inspiration - active process - diaphragm descends and external intercostal
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