Structure and Function of the Pulmonary System Chapter 32 Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.

2 Structures of the Pulmonary System  Airways  Blood vessels  Chest wall  Lungs  Lobes  Segments  Lobules

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 3 Structures of the Pulmonary System

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 4 Structures of the Pulmonary System  Conducting airways  Upper airways Nasopharynx Nasopharynx Oropharynx Oropharynx  Larynx Connects upper and lower airways Connects upper and lower airways  Lower airways Trachea Trachea Bronchi Bronchi Terminal bronchioles Terminal bronchioles

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 5 Structures of the Pulmonary System

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 6 Structures of the Pulmonary System  Gas-exchange airways  Respiratory bronchioles  Alveolar ducts  Alveoli Epithelial cells Epithelial cells  Type I alveolar cells –Alveolar structure  Type II alveolar cells –Surfactant production

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 7 Structures of the Pulmonary System

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 8 Structures of the Pulmonary System

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 9 Structures of the Pulmonary System

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 10 Gas Exchange  Alveoli  Primary gas-exchange units  Pores of Kohn Permit air to pass through the septa from alveolus to alveolus Permit air to pass through the septa from alveolus to alveolus  Collateral ventilation and even air distribution  Lungs contain approximately 25 million alveoli at birth and 300 million by adulthood

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 11 Pulmonary and Bronchial Circulation  Pulmonary circulation has a lower pressure than systemic circulation (18 mmHg)  Only one third of vessels filled with blood at any given time

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 12 Pulmonary and Bronchial Circulation  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 © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 13 Pulmonary and Bronchial Circulation

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 14 Pulmonary and Bronchial Circulation  Alveolocapillary membrane  Formed by 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 © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 15 Pulmonary and Bronchial Circulation

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 16 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 © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 17 Lung Functions  Gas exchange  Supply oxygen  Eliminate CO 2  Maintain pH  Eliminate water  Other functions  Maintain normal body temperature  Immune responses  Hormone secretion  Metabolism

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 18 Requirements for Ventilation, Perfusion, and Diffusion  Adequate inspired O 2 – (Fi O 2 )  Ventilation and perfusion of alveoli  A permeable alveolocapillary membrane  Adequate blood flow  Ability to transport O 2 and CO 2  Ability of cell to use O 2 and eliminate CO 2

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 19 Requirements for Ventilation, Perfusion, and Diffusion  Adequate inspired O 2 – (FiO 2 ) Barometric pressure is 760 at sea level 21% x 760 = partial pressure of O 2 at sea level = ~160 mmHg Barometric pressure is 600 at Salt Lake City (much lower on Mt. Everest) (much lower on Mt. Everest) 21% x 600 = partial pressure of O 2 at SLC = ~126 mmHg Why we give oxygen at high altitude

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 20 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 Ventilatory rate multiplied by the volume of air per breath  Alveolar ventilation

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 21 Lung Volumes and Capacities Based on Age, Gender, Height  Dead space: oropharynx to division 16 (about equal to ideal body weight)  Tidal volume (per breath) ml  IRV 3000 ml additional air that could be inhaled

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 22 Lung Volumes and Capacities Based on Age, Gender, Height  ERV 1000 ml remaining air  Can be forcefully expired after normal expiration FEV 1  Why abdominal thrusts work; expel TV plus ERV  Forced vital capacity (theoretical)  TV + IRV + ERV ~ ml  Residual volume constant ~1200 ml  Air remaining in alveoli

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 23 Formulas  Minute ventilation (or volume/min)  RR x TV  RR 16, TV 500  16 x 500 = 8000 ml/min  Effective minute volume: RR x (TV-DS)  100 lb, RR 16, TV 500 ml  16 ( ) = 6400 ml/min

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 24 Control of Ventilation  ANS  Stimulates smooth muscle (contract relax) Airway lumen diameter Airway lumen diameter

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 25 Terms  Hypoxia  Low oxygen in the cell  Hypoxemia  Low oxygen in arterial blood (low O 2 saturation)

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 26 Control of Ventilation  Chemoreceptors  Central receptors Reflects Pa CO 2 Reflects Pa CO 2 Stimulated by H + in cerebrospinal fluid (pH) Stimulated by H + in cerebrospinal fluid (pH)  Peripheral receptors Aorta and carotid bodies Aorta and carotid bodies Stimulated by hypoxemia (Pa O 2 ) Stimulated by hypoxemia (Pa O 2 )

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 27 Control of Ventilation  Irritant receptors: epithelium of conducting airways  Cough, bronchoconstriction, decrease RR  Stretch receptors: protective  Decrease RR and volume

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 28 Ventilation  Neurochemical control  Respiratory center Dorsal respiratory group Dorsal respiratory group Ventral respiratory group Ventral respiratory group Pneumotaxic center Pneumotaxic center Apneustic center Apneustic center  Peripheral chemoreceptors

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 29 Ventilation  Neurochemical control  Lung receptors Irritant receptors Irritant receptors Stretch receptors Stretch receptors J-receptors J-receptors  Chemoreceptors Central chemoreceptors Central chemoreceptors Peripheral chemoreceptors Peripheral chemoreceptors

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 30 Mechanics of Breathing  Major and accessory muscles  Major muscles of inspiration Diaphragm Diaphragm External intercostals External intercostals  Accessory muscles of inspiration Sternocleidomastoid and scalene muscles Sternocleidomastoid and scalene muscles  Accessory muscles of expiration Abdominal and internal intercostal muscles Abdominal and internal intercostal muscles

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 31 Muscles of Ventilation

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 32 Overview: Mechanics of Breathing  Alveolar surface tension  Function of surfactant  Elastic properties of lung and chest wall  Elastic recoil  Compliance  Airway resistance  Airway size  Gas velocity (Poiseuille’s law)  Muscular effort

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 33 Mechanics of Breathing

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 34 Surface Tension of Water  Tendency of water molecules to contract to the smallest possible surface area (bead) with exposure to air  Increased surface tension = increased work of breathing

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 35 Laplace’s Law  The smaller a sphere’s radius (alveoli) the greater the surface tension and the more difficult (work) to expand the alveoli  P = 2t/r  P = pressure inside a sphere (alveoli)  t = surface tension  r = radius of a sphere  Surfactant reduces fluid surface tension lining the alveoli and decreases tendency to collapse, preventing atelectasis

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 36 Compliance  A measure of lung and chest wall distensibility or “stiffness”  ― volume of air moved ― force to move the air ― force to move the air  Low: increased work of inspiration  Stiff lungs  High: increased work of expiration  Baggy lungs

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 37 Measurement of Gas Pressure  Barometric pressure  Partial pressure  Partial pressure of water vapor

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 38 Measurement of Gas Pressure

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 39 Measurement of Gas Pressure

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 40 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 © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 41 Gas Transport  Distribution of ventilation and perfusion  Gravity and alveolar pressure  Ventilation-perfusion ratio

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 42 Gas Transport: O 2  Oxygen transport  Diffusion across alveolocapillary membrane  Determinants of arterial oxygenation  Oxyhemoglobin association and dissociation Oxyhemoglobin dissociation curve Oxyhemoglobin dissociation curve

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 43 Gas Transport: CO 2  Carbon dioxide transport  Dissolved in plasma  Bicarbonate  Carbamino compounds  Haldane effect

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 44 Measurement of Gas Pressure

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 45 Measurement of Gas Pressure

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 46 Clinical Manifestations: Hypoxemia  Early  Tachycardia  Mild increase in blood pressure  Diaphoresis (stress response)  Confusion (CNS response)  Loss of judgment  Cyanosis after 5 g desaturation  Late  Stupor  Decreased BP, myocardium not getting enough O 2

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 47 Control of Pulmonary Circulation  Hypoxic vasoconstriction  Caused by low alveolar PO 2  Blood is shunted to other, well-ventilated portions of the lungs Better ventilation and perfusion matching Better ventilation and perfusion matching If hypoxia affects all segments of lungs, the vasoconstriction can result in pulmonary hypertension If hypoxia affects all segments of lungs, the vasoconstriction can result in pulmonary hypertension  Acidemia also causes pulmonary artery constriction

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 48 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 © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 49 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 © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 50 Aging and the Pulmonary System