1 Structure and Function of the Pulmonary System Chapter 32

Mosby items and derived items © 2006 by Mosby, Inc. 2 Structures of the Pulmonary System  Airways  Blood vessels  Chest wall  Lungs Lobes Segments Lobules

Mosby items and derived items © 2006 by Mosby, Inc. 3 Structures of the Pulmonary System

Mosby items and derived items © 2006 by Mosby, Inc. 4 Structures of the Pulmonary System  Conducting airways Upper airways  Nasopharynx  Oropharynx Larynx  Connects upper and lower airways Lower airways  Trachea  Bronchi  Terminal bronchioles

Mosby items and derived items © 2006 by Mosby, Inc. 5 Structures of the Pulmonary System

Mosby items and derived items © 2006 by Mosby, Inc. 6 Structures of the Pulmonary System  Gas-exchange airways Respiratory bronchioles Alveolar ducts Alveoli  Epithelial cells Type I alveolar cells  Alveolar structure Type II alveolar cells  Surfactant production

Mosby items and derived items © 2006 by Mosby, Inc. 7 Structures of the Pulmonary System

Mosby items and derived items © 2006 by Mosby, Inc. 8 Structures of the Pulmonary System

Mosby items and derived items © 2006 by Mosby, Inc. 9 Structures of the Pulmonary System

Mosby items and derived items © 2006 by Mosby, Inc. 10 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

Mosby items and derived items © 2006 by Mosby, Inc. 11 Pulmonary and Bronchial Circulation

Mosby items and derived items © 2006 by Mosby, Inc. 12 Pulmonary and Bronchial Circulation  Alveolocapillary membrane Formed by the shared alveolar and capillary walls Thin membrane of alveolar epithelium, the alveolar basement membrane, interstitial space, the capillary basement membrane, and the capillary endothelium

Mosby items and derived items © 2006 by Mosby, Inc. 13 Pulmonary and Bronchial Circulation

Mosby items and derived items © 2006 by Mosby, Inc. 14 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

Mosby items and derived items © 2006 by Mosby, Inc. 15 Function of the Pulmonary System  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

Mosby items and derived items © 2006 by Mosby, Inc. 16 Ventilation  Neurochemical control Respiratory center  Dorsal respiratory group  Ventral respiratory group  Pneumotaxic center  Apneustic center Peripheral chemoreceptors

Mosby items and derived items © 2006 by Mosby, Inc. 17 Ventilation  Neurochemical control Lung receptors  Irritant receptors  Stretch receptors  J-receptors Chemoreceptors  Central chemoreceptors  Peripheral chemoreceptors

Mosby items and derived items © 2006 by Mosby, Inc. 18 Mechanics of Breathing  Major and accessory muscles Major muscles of inspiration  Diaphragm  External intercostals Accessory muscles of inspiration  Sternocleidomastoid and scalene muscles Accessory muscles of expiration  Abdominal and internal intercostal muscles

Mosby items and derived items © 2006 by Mosby, Inc. 19 Muscles of Ventilation

Mosby items and derived items © 2006 by Mosby, Inc. 20 Mechanics of Breathing  Alveolar surface tension Function of surfactant  Elastic properties of the lung and chest wall Elastic recoil Compliance  Airway resistance  Work of breathing

Mosby items and derived items © 2006 by Mosby, Inc. 21 Mechanics of Breathing

Mosby items and derived items © 2006 by Mosby, Inc. 22 Measurement of Gas Pressure  Barometric pressure Partial pressure  Partial pressure of water vapor

Mosby items and derived items © 2006 by Mosby, Inc. 23 Measurement of Gas Pressure

Mosby items and derived items © 2006 by Mosby, Inc. 24 Measurement of Gas Pressure

Mosby items and derived items © 2006 by Mosby, Inc. 25 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 CO 2 occurs in reverse order

Mosby items and derived items © 2006 by Mosby, Inc. 26 Gas Transport  Distribution of ventilation and perfusion Gravity and alveolar pressure Ventilation-perfusion ratio

Mosby items and derived items © 2006 by Mosby, Inc. 27 Measurement of Gas Pressure

Mosby items and derived items © 2006 by Mosby, Inc. 28 Gas Transport  Oxygen transport Diffusion across the alveolocapillary membrane Determinants of arterial oxygenation Oxyhemoglobin association and dissociation  Oxyhemoglobin dissociation curve

Mosby items and derived items © 2006 by Mosby, Inc. 29 Measurement of Gas Pressure

Mosby items and derived items © 2006 by Mosby, Inc. 30 Gas Transport  Carbon dioxide transport Dissolved in plasma Bicarbonate Carbamino compounds  Haldane effect

Mosby items and derived items © 2006 by Mosby, Inc. 31 Control of Pulmonary Circulation  Hypoxic vasoconstriction Caused by low alveolar pO 2 Blood is shunted to other, well-ventilated portions of the lungs  Provides better ventilation and perfusion matching  If hypoxia affects all segments of the lungs, the vasoconstriction can result in pulmonary hypertension  Acidemia also causes pulmonary artery constriction

Mosby items and derived items © 2006 by Mosby, Inc. 32 Tests of Pulmonary Function  Spirometry  Diffusion capacity  Residual volume  Functional reserve capacity (FRC)  Total lung capacity  Arterial blood gas analysis  Chest radiographs

Mosby items and derived items © 2006 by Mosby, Inc. 33 Aging and the Pulmonary System  Loss of elastic recoil  Stiffening of the chest wall  Alterations in gas exchange  Increases in flow resistance

Mosby items and derived items © 2006 by Mosby, Inc. 34 Aging and the Pulmonary System