Chapter 26: Structure and Function of the Pulmonary System - Mosby PDF

Chapter 26 Structure and Function of the Pulmonary System  Structures of the Pulmonary System  Conducting airways: Upper airways: Nasopharynx Oropharynx Larynx Connects upper and lower airways Lower airw...

Chapter 26 Structure and Function of the Pulmonary System  Structures of the Pulmonary System  Conducting airways: Upper airways: Nasopharynx Oropharynx Larynx Connects upper and lower airways Lower airways: Trachea Bronchi Terminal bronchioles  Structures of the Pulmonary System (Cont.)  Gas-exchange airways: Respiratory bronchioles Alveolar ducts Alveoli Epithelial cells:  Type I alveolar cells – Alveolar structure  Type II alveolar cells – Surfactant production Macrophages  Immune protection  Structures of the Pulmonary System (Cont.) From Patton, K.T., & Thibodeau, G.A. (2016). Structure & function of the body (15th ed.). Mosby.  Structures of the Pulmonary System (Cont.) Redrawn from Thompson, J.M., et al. (2002). Mosby’s clinical nursing (5th ed.). Mosby.  Structures of the Pulmonary System (Cont.) From Patton, K.T., & Thibodeau, G.A. (2018). The human body in health & disease (7th ed.). Elsevier. 1. Which statement is TRUE regarding the pulmonary system? A. Each lobe is divided into bronchi. B. Left lobe is divided into three lobes. C. Mediastinum contains the lungs and heart. D. Larynx connects the upper and lower airways.  Pulmonary and Bronchial Circulation  Pulmonary circulation has a lower pressure than the systemic circulation.  One-third of pulmonary vessels are filled with blood at any given time.  Pulmonary artery divides and enters the lung at the hilus.  Each bronchus and bronchiole has an accompanying artery or arteriole.  Pulmonary and Bronchial Circulation (Cont.)  Alveolocapillary membrane Formed by the shared alveolar and capillary walls Gas exchange occurs across this membrane  Pulmonary veins Each drains several pulmonary capillaries Dispersed randomly throughout the lung Leave the lung at the hila and enter the left atrium  Pulmonary and Bronchial Circulation (Cont.) Adapted from Montague, S.E., Watson, R., & Herbert, R. (2005). Physiology for nursing practice (3rd ed.). Elsevier.  Control of the Pulmonary Circulation  Calibre of pulmonary artery lumina decreases as smooth muscle in the arterial walls contracts.  Contraction (vasoconstriction) and relaxation (vasodilation) primarily occur in response to local humoral conditions. Most important cause of pulmonary artery constriction is a low alveolar PO2. Acidemia also causes pulmonary artery constriction.  Chest Wall and Pleura  Chest wall Skin, ribs, and intercostal muscles Thoracic cavity  Pleura Serous membrane Parietal and visceral layers Pleural space (cavity) Pleural fluid  Thoracic Cavity From Thibodeau, G.A., & Patton, K.T. (1996). Anatomy & physiology (3rd ed.). Mosby. Functions of the Pulmonary System  Ventilate the alveoli  Diffuse gases into and out of the blood  Perfuse the lungs so the body receives oxygen  Functions of the Pulmonary System (Cont.)  Ventilation Mechanical movement of gas or air into and out of the lungs Minute volume Ventilatory rate multiplied by the volume of air per breath Alveolar ventilation  Ventilation  Neurochemical control Respiratory centre Lung receptors: Dorsal respiratory Irritant receptors group Stretch receptors Ventral respiratory J receptors group Chemoreceptors: Pneumotaxic centre Central chemoreceptors Apneustic centre Peripheral Peripheral chemoreceptors chemoreceptors Neurochemical Respiratory Control  Mechanics of Breathing  Major and accessory muscles: Major muscles of inspiration: Diaphragm External intercostals Accessory muscles of inspiration: Sternocleidomastoid muscle Scalene muscles Accessory muscles of expiration: No major muscles of expiration; normally passive Abdominal muscles Internal intercostal muscles Muscles of Ventilation Modified from Thompson, J.M., et al. (2002). Mosby’s clinical nursing (5th ed.). Mosby.  Mechanics of Breathing  Alveolar surface tension and ventilation Function of surfactant  Elastic properties of the lung and chest wall: Elastic recoil Compliance  Airway resistance  Work of breathing Mechanics of Breathing (Cont.) 2. A patient has a history of emphysema and has hyperinflated lungs. Which of the following would be TRUE regarding this patient? A. Increased compliance B. Decreased surfactant C. Increased elastic recoil D. Increased airway resistance  Gas Transport  Four steps Ventilation of the lungs Diffusion of oxygen from the alveoli into the capillary blood Perfusion of systemic capillaries with oxygenated blood Diffusion of oxygen from systemic capillaries into the cells  Diffusion of CO2 occurs in reverse order  Measurement of Gas Pressure  Barometric pressure Partial pressure  Partial pressure of water vapour Measurement of Gas Pressure (Cont.) Modified from Thompson, J.M., et al. (2002). Mosby’s clinical nursing (5th ed.). Mosby. Measurement of Gas Pressure From Patton, K.T., & Thibodeau, G.A. (2010). The human body in health & disease (4th ed.). Mosby.  Gas Transport  Distribution of ventilation and perfusion Gravity and alveolar pressure Ventilation–perfusion ratio Normal = 0.8  Gas Transport (Cont.)  Oxygen transport Diffusion across the alveolocapillary membrane Determinants of arterial oxygenation: Hemoglobin binding Oxygen saturation Oxyhemoglobin association and dissociation Oxyhemoglobin dissociation curve Bohr effect  Gas Transport  Carbon dioxide transport Dissolved in plasma Bicarbonate Carbamino compounds  Haldane effect  Aging and the Pulmonary System  Decreased chest wall compliance and elastic recoil of the lungs Reduces ventilatory reserve  Decreased surface area for gas exchange as well as capillary perfusion decreasing exercise capacity