Pulmonary Physiology: Respiratory System Study Guide PDF

Part 1 Pulmonary 1) Students will identify the parts of the conducting and respiratory zones of the lungs and will interpret the functions of lung volumes and capacities. The respiratory system includes the lungs and a series of airways that connect the lungs to the external environment. The struc...

Part 1 Pulmonary 1) Students will identify the parts of the conducting and respiratory zones of the lungs and will interpret the functions of lung volumes and capacities. The respiratory system includes the lungs and a series of airways that connect the lungs to the external environment. The structures of the respiratory system are subdivided into a conducting zone (or conducting airways), which brings air into and out of the lungs, and a respiratory zone lined with alveoli where gas exchange occurs. The functions of the conducting and respiratory zones differ, and the structures lining them also differ. Conducting zone The conducting zone includes the nose, nasopharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles. These structures function to bring air into and out of the respiratory zone for gas exchange and to warm, humidify, and filter the air before it reaches the critical gas exchange region. The progressively bifurcating airways are referred to by their generation number. The trachea, which is the zeroth generation, is the main conducting airway. The trachea divides into the right and left mainstem bronchi (the first generation), which divide into smaller bronchi, continuing this process through 23 generations, culminating in the airways of the 23rd generation. Cartilage is present in the walls of the zeroth to 10th generations of conducting airways; it functions structurally to keep those airways open. Starting with the 11th generation, cartilage disappears; to remain open, those airways with no cartilage depend on the presence of a favorable transmural pressure. The conducting airways are lined with mucus-secreting and ciliated cells that function to remove inhaled particles. Large particles are usually filtered out in the nose, while small particles are captured by mucus and swept upward by the rhythmic beating of cilia. The walls of the conducting airways contain smooth muscle, which is regulated by the autonomic nervous system: 1. Sympathetic adrenergic neurons activate β₂ receptors on bronchial smooth muscle, leading to relaxation and dilation of the airways. These β₂ receptors are also activated by epinephrine from the adrenal medulla and by β₂-adrenergic agonists such as isoproterenol. 2. Parasympathetic cholinergic neurons activate muscarinic receptors, leading to contraction and constriction of the airways. Changes in airway diameter affect airway resistance, altering air flow. β₂-adrenergic agonists (e.g., epinephrine, isoproterenol, albuterol) are used to dilate airways in the treatment of asthma. Part 1 Pulmonary Respiratory zone The respiratory zone includes structures lined with alveoli and thus involved in gas exchange: the respiratory bronchioles, alveolar ducts, and alveolar sacs. Respiratory bronchioles are transitional structures—they have cilia and smooth muscle, like the conducting airways, but also participate in gas exchange as alveoli occasionally bud off their walls. Alveolar ducts are completely lined with alveoli, but they contain no cilia and little smooth muscle. Alveolar sacs are the terminal structures of the respiratory zone, also lined with alveoli. Alveoli are pouchlike evaginations of the respiratory bronchioles, alveolar ducts, and alveolar sacs. Each lung contains approximately 300 million alveoli, with a diameter of ~200 micrometers (μm). The thin alveolar walls and large surface area allow rapid and efficient diffusion of oxygen (O₂) and carbon dioxide (CO₂) between alveolar gas and pulmonary capillary blood. The alveolar walls contain elastic fibers and epithelial cells called type I and type II pneumocytes (alveolar cells): Type II pneumocytes synthesize pulmonary surfactant, which reduces surface tension in the alveoli, and they have regenerative capacity for type I and type II pneumocytes. The alveoli also contain phagocytic cells called alveolar macrophages, which keep the alveoli free of dust and debris since alveoli have no cilia. Macrophages migrate to the bronchioles, where cilia transport debris to the pharynx for swallowing or expectoration. 2) Students will calculate ventilation rates, dilution effect of dead space, alveolar ventilation, alveolar PO2 and FEV1 /FVC ratios. 3) Students will examine the mechanics of breathing: muscles involved, compliance of lungs and chest wall, FRC as the equilibrium point and the impact of diseases upon compliance. 4) Students will recognize the molecular forces responsible for and the importance of alveolar surface tension in maintaining effective gas exchange across respiratory membranes. 5) Students will recognize the importance of the pressure gradient and resistance (Poiseuille Law) upon the effectiveness of ventilation (air flow). 6) Students will assess changes in volumes and pressures occurring during a normal breathing cycle. Part 1 Pulmonary