Respiratory Tract

The Upper Respiratory Tract
The human respiratory system involves complex organization of structural and defense mechanisms for the inhalation and exhalation of gases. The primary function of the respiratory system is to breathe air, provide oxygen to the bloodstream, and expel carbon dioxide. The respiratory system also provides transport of respiratory gases, internal respiration, pulmonary ventilation, and external respiration. There are two zones of the respiratory system, the conducting zone and the respiratory zone. The conducting zone is comprised of structured conduits for air to flow to sites of gas exchange and includes the nose, nasal cavity, pharynx, larynx, trachea, and bronchi. The respiratory zone is a site of gas exchange
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During passive or quiet breathing, the muscles used for ventilation are the diaphragm, external intercostals, scalenes, and sternocleidomastoids (pg. 536 Silverthorn). Inhalation and exhalation begin with the contraction and relaxation of the diaphragm, a dome-shaped muscle beneath the lungs. The diaphragm’s contraction downward provides a vacuum of pressure differences to bring air into the lungs. During exhalation, the diaphragm is relaxed upwards, pushing air out of the lungs. The lungs have a spongy tissue with its volume engaged in air-filled spaces. The lungs are covered in a double layered serosa where the parietal pleura lines the thoracic wall and the visceral pleura covers the lung surface. Each lung is surrounded by the pleura fluid which is engrossed in between two pleura membrane. This pleura fluid serves as a moist surface to prevent friction as well as adhere the lungs tightly together in between the thoracic wall. ( pg.536,Silverthorn) The intrapleural pressure of the pleura fluid is -3 mm Hg and as a result, the pressure from the lungs will rush out towards the pleural membrane due to a high to low pressure gradient, consistent with Boyle’s law with increased volume causes a decrease in intrapleural pressure. Airway resistance, friction, and bronchiole constriction also play factors into respiratory

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