8/25/2023 The trachea, bronchi, and terminal bronchioles contribute to anatomic dead space because:Read Now![]() Pressure is determined by the volume of the space occupied by a gas and is influenced by resistance. In addition, intra-alveolar pressure will equalize with the atmospheric pressure. The difference in pressure between intrapleural and intra-alveolar pressures is called transpulmonary pressure. Typically, intrapleural pressure is lower, or negative to, intra-alveolar pressure. The force exerted by gases within the alveoli is called intra-alveolar (intrapulmonary) pressure, whereas the force exerted by gases in the pleural cavity is called intrapleural pressure. Atmospheric pressure is the force exerted by gases present in the atmosphere. Pulmonary ventilation is the process of breathing, which is driven by pressure differences between the lungs and the atmosphere. The mesothelial cells of the pleural membrane create pleural fluid, which serves as both a lubricant (to reduce friction during breathing) and as an adhesive to adhere the lungs to the thoracic wall (to facilitate movement of the lungs during ventilation). The space between these two layers is called the pleural cavity. The lungs are enclosed by the pleura, a membrane that is composed of visceral and parietal pleural layers. The lungs are innervated by the parasympathetic and sympathetic nervous systems, which coordinate the bronchodilation and bronchoconstriction of the airways. The pulmonary artery provides deoxygenated blood to the capillaries that form respiratory membranes with the alveoli, and the pulmonary veins return newly oxygenated blood to the heart for further transport throughout the body. The function of the pulmonary circulation is to aid in gas exchange. Blood circulation is very important, as blood is required to transport oxygen from the lungs to other tissues throughout the body. The lungs are paired and separated into lobes The left lung consists of two lobes, whereas the right lung consists of three lobes. The lungs are the major organs of the respiratory system and are responsible for performing gas exchange. This is a blood-air barrier through which gas exchange occurs by simple diffusion. The endothelium of the surrounding capillaries, together with the alveolar epithelium, forms the respiratory membrane. As the bronchioles become smaller and smaller, and nearer the alveoli, the epithelium thins and is simple squamous epithelium in the alveoli. The mucus traps pathogens and debris, whereas beating cilia move the mucus superiorly toward the throat, where it is swallowed. The lining of the conducting zone is composed mostly of pseudostratified ciliated columnar epithelium with goblet cells. ![]() The respiratory zone includes the structures of the lung that are directly involved in gas exchange: the terminal bronchioles and alveoli. The pharynx is composed of three major sections: the nasopharynx, which is continuous with the nasal cavity the oropharynx, which borders the nasopharynx and the oral cavity and the laryngopharynx, which borders the oropharynx, trachea, and esophagus. The nasal passages contain the conchae and meatuses that expand the surface area of the cavity, which helps to warm and humidify incoming air, while removing debris and pathogens. The conducting zone consists of all of the structures that provide passageways for air to travel into and out of the lungs: the nasal cavity, pharynx, trachea, bronchi, and most bronchioles. From a functional perspective, the respiratory system can be divided into two major areas: the conducting zone and the respiratory zone. The respiratory system is responsible for obtaining oxygen and getting rid of carbon dioxide, and aiding in speech production and in sensing odors. 22.1 Organs and Structures of the Respiratory System
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