Chapter 25 Structure and Function of the Pulmonary

Chapter 25 Structure and Function of the Pulmonary System Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 1

Structures of the Pulmonary System Airways Pulmonary circulation Chest wall Lungs Ø Ø Ø Lobes (three on right, two on left) Segments Lobules Mediastinum Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 2

Structures of the Pulmonary System (cont’d) Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 3

Structures of the Pulmonary System (cont’d) Conducting airways: Upper airways: • Nasopharynx • Oropharynx Ø Larynx • Connects upper and lower airways Ø Lower airways: • Trachea • Bronchi • Terminal bronchioles Ø Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 4

Structures of the Pulmonary System (cont’d) Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 5

Structures of the Pulmonary System (cont’d) Gas-exchange airways: Ø Ø Ø Respiratory bronchioles Alveolar ducts Alveoli • Epithelial cells: Type I alveolar cells – Alveolar structure Type II alveolar cells – Surfactant production Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 6

Structures of the Pulmonary System (cont’d) Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 7

Structures of the Pulmonary System (cont’d) Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 8

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 © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 9

Pulmonary and Bronchial Circulation (cont’d) Alveolocapillary membrane Formed by the shared alveolar and capillary walls Ø Gas exchange occurs across this membrane Ø Pulmonary veins Ø Ø Ø Each drains several pulmonary capillaries Dispersed randomly throughout the lung Leave the lung at the hila and enter the left atrium Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 10

Pulmonary and Bronchial Circulation (cont’d) Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 11

Chest Wall and Pleura Chest wall Ø Ø Skin, ribs, and intercostal muscles Thoracic cavity Pleura Ø Ø Serous membrane Parietal and visceral layers Pleural space (cavity) Pleural fluid Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 12

Thoracic Cavity Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 13

Function of the Pulmonary System Ventilate the alveoli Diffuse gases into and out of the blood Perfuse the lungs so the body receives oxygen Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 14

Function of the Pulmonary System (cont’d) Ventilation Mechanical movement of gas or air into and out of the lungs Ø Minute volume • Ventilatory rate multiplied by the volume of air per Ø breath Ø Alveolar ventilation Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 15

Ventilation Neurochemical control Ø Respiratory center • Dorsal respiratory group • Ventral respiratory group • Pneumotaxic center • Apneustic center Ø Peripheral chemoreceptors Lung receptors: • Irritant receptors • Stretch receptors • J receptors Ø Chemoreceptors: • Central Ø chemoreceptors • Peripheral chemoreceptors Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 16

Neurochemical Respiratory Control Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 17

Mechanics of Breathing Major and accessory muscles: Major muscles of inspiration: • Diaphragm • External intercostals Ø Accessory muscles of inspiration: • Sternocleidomastoid muscle • Scalene muscles Ø Accessory muscles of expiration: • Abdominal intercostal muscles • Internal intercostal muscles Ø Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 18

Muscles of Ventilation Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 19

Mechanics of Breathing Alveolar surface tension and ventilation Ø Elastic properties of the lung and chest wall: Ø Ø Function of surfactant Elastic recoil Compliance Airway resistance Work of breathing Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 20

Mechanics of Breathing (cont’d) Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 21

Gas Transport Four steps Ventilation of the lungs Diffusion of oxygen from the alveoli into the capillary blood Ø Perfusion of systemic capillaries with oxygenated blood Ø Diffusion of oxygen from systemic capillaries into the cells Ø Ø Diffusion of CO 2 occurs in reverse order Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 22

Measurement of Gas Pressure Barometric pressure Ø Partial pressure of water vapor Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 23

Measurement of Gas Pressure (cont’d) Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 24

Gas Transport Distribution of ventilation and perfusion Ø Ø Gravity and alveolar pressure Ventilation-perfusion ratio Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 25

Gas Transport (cont’d) Oxygen transport Diffusion across the alveolocapillary membrane Determinants of arterial oxygenation: • Hemoglobin binding • Oxygen saturation Ø Oxyhemoglobin association and dissociation • Oxyhemoglobin dissociation curve • Bohr effect Ø Ø Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 26

Measurement of Gas Pressure Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 27

Gas Transport Carbon dioxide transport Ø Ø Ø Dissolved in plasma Bicarbonate Carbamino compounds Haldane effect Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 28

Control of Pulmonary Circulation Hypoxic pulmonary vasoconstriction Ø Ø Caused by low alveolar pa. O 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 Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 29

Control of Pulmonary Circulation (cont’d) Acidemia also causes pulmonary artery constriction Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 30

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 © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 31

Aging and the Pulmonary System Loss of elastic recoil Stiffening of the chest wall Alterations in gas exchange Increases in flow resistance Decreased exercise tolerance Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 32

Aging and the Pulmonary System (cont’d) Mosby items and derived items © 2012 Mosby, Inc. , an imprint of Elsevier Inc. 33