Transcript chapter 19
Hole’s Human Anatomy and Physiology Twelfth Edition Shier w Butler w Lewis Chapter 19 Respiratory System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 19.1: Introduction • The respiratory system consists of passages that filter incoming air and transport it into the body, into the lungs, and to the many microscopic air sacs where gases are exchanged • Respiration is the process of exchanging gases between the atmosphere and body cells • It consists of the following events: • Ventilation • External respiration • Transport of gases • Internal respiration • Cellular respiration 2 19.2: Why We Breathe • Respiration occurs on a macroscopic level at the organ system • Gas exchange, oxygen and carbon dioxide, occur at the cellular and molecular levels • Aerobic reactions of cellular respiration allow for: • ATP production • Carbon dioxide generation forming carbonic acid 3 19.3: Organs of the Respiratory System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • The organs of the respiratory system can be divided into two tracts: • Upper respiratory tract • The nose • Nasal cavity • Sinuses • Pharynx • Lower respiratory tract • Larynx • Trachea • Bronchial tree • Lungs Frontal sinus Nasal cavity Hard palate Soft palate Pharynx Nostril Oral cavity Larynx Epiglottis Esophagus Trachea Bronchus 4 Right lung Left lung Nose Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Frontal sinus Superior Middle Inferior Nasal conchae Sphenoidal sinus Nostril Hard palate Uvula Tongue Hyoid bone Pharyngeal tonsil Nasopharynx Opening of auditory tube Palatine tonsil Oropharynx Lingual tonsil Epiglottis Laryngopharynx Larynx Trachea Esophagus 5 Nasal Cavity Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nasal cavity Mucus Particle Cilia Goblet cell Epithelial cell (a) (b) b: © Biophoto Associates/Photo Researchers, Inc. pseudostratified columnar epithelium with cilia and goblet cells 6 Sinuses • The sinuses are air-filled spaces in the maxillary, frontal, ethmoid, and sphenoid bones of the skull 7 Pharynx • The pharynx is posterior to the oral cavity and between the nasal cavity and the larynx Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Superior Frontal sinus Middle Inferior Nasal conchae Sphenoidal sinus Nostril Pharyngeal tonsil Hard palate Uvula Tongue Nasopharynx Opening of auditory tube Palatine tonsil Oropharynx Lingual tonsil Epiglottis Hyoid bone Laryngopharynx Larynx Trachea Esophagus 8 Larynx • The larynx is an enlargement in the airway superior to the trachea and inferior to the pharynx • It is composed of a framework of muscles and cartilages bound by elastic tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Epiglottic cartilage Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Epiglottis Hyoid bone False vocal cord Thyroid cartilage Glottis Cricoid cartilage True vocal cord (a) Thyroid cartilage Cuneiform cartilage Hyoid bone Epiglottis Arytenoid cartilage False vocal cord Thyroid cartilage True vocal cord Cricoid cartilage Corniculate cartilage Hyoid bone (b) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thyroid cartilage Posterior portion of tongue Cricoid cartilage Glottis False vocal cord True vocal cord Cuneiform cartilage Corniculate cartilage (a) Trachea (a) Epiglottis Glottis Inner lining of trachea Hyoid bone (b) Epiglottic cartilage Thyroid cartilage 9 Cricoid cartilage Trachea (b) (c) c: © CNRI/PhotoTake Trachea Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • The trachea (windpipe) is a flexible cylindrical tube about 2.5 centimeters in diameter and 12.5 centimeters in length • As it extends downward anterior to the esophagus and into the thoracic cavity, it splits into the right and left primary bronchi Larynx Thyroid cartilage Cricoid cartilage Trachea Superior (upper) lobe bronchus Cartilaginous ring Carina Left primary bronchus Right primary bronchus Middle lobe bronchus Superior (upper) lobe bronchus Inferior (lower) lobe bronchi 10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lumen of trachea Hyaline cartilage Ciliated epithelium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hyoid bone Smooth muscle Connective tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Connective tissue Smooth muscle Thyroid cartilage Thyroid gland Cricoid cartilage Incision Trachea Jugular notch Hyaline cartilage Ciliated epithelium Lumen of trachea © Ed Reschke 11 Bronchial Tree • The bronchial tree consists of branched airways leading from the trachea to the microscopic air sacs in the lungs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Larynx Trachea Right superior (upper) lobe Left superior (upper) lobe Right primary bronchus Secondary bronchus Tertiary bronchus Terminal bronchiole Right inferior (lower) lobe Right middle lobe Left inferior (lower) lobe Respiratory bronchiole Alveolar duct Alveolus 12 Branches of the Bronchial Tree • The successive divisions of the branches from the trachea to the alveoli are: 1. Right and left primary bronchi 2. Secondary or lobar bronchi 3. Tertiary or segmental bronchi 4. Intralobular bronchioles 5. Terminal bronchioles 6. Respiratory bronchioles 7. Alveolar ducts 8. Alveolar sacs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Ralph Hutchings/Visuals Unlimited 13 Blood flow Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood flow Intralobular bronchiole Pulmonary venule Pulmonary arteriole Blood flow Smooth muscle Alveolus Pulmonary artery Capillary network on surface of alveolus Pulmonary vein Terminal bronchiole Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Respiratory bronchiole Alveolar duct Alveolar sac Alveoli Capillary Simple squamous epithelial cells Alveolus © McGraw-Hill Higher Education, Inc./Bob Coyle 14 The Respiratory Tubes • The structure of the bronchus is similar to that of the trachea, but the C-shaped cartilaginous rings are replaced with cartilaginous plates where the bronchus enters the lung • These respiratory tubes become thinner and thinner, and the cell layers thin and change until the alveoli is reached • It is the alveoli that provides surface area for gas exchange Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood flow Blood flow Venule Arteriole Alveolar wall Alveolus Air O2 CO2 CO2 O2 Capillary 15 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood vessel Capillary Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Alveolus Tissues and Organs: A Text-Atlas of Scanning Electron Microscopy, by R.G. Kessel and R.H. Kardon. © 1979 W.H. Freeman and Company Alveolus Bronchiole Courtesy of the American Lung Association 16 Lungs • The right and left lungs are soft, spongy, cone-shaped organs in the thoracic cavity • The right lung has three lobes and the left lung two lobes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Right lung Left lung Thyroid cartilage Cricoid cartilage Plane of section Trachea Clavicle Scapula Superior (upper) lobe of right lung Superior (upper) lobe of left lung Middle lobe of right lung Inferior (lower) lobe of left lung Inferior (lower) lobe of right lung Heart Visceral pleura Pericardial cavity Parietal pleura Pericardium Pleura Right pleural cavity Left pleural cavity Rib cartilage Sternum 17 18 19.4: Breathing Mechanism • Breathing or ventilation is the movement of air from outside of the body into the bronchial tree and the alveoli • The actions responsible for these air movements are inspiration, or inhalation, and expiration, or exhalation 19 Inspiration • Atmospheric pressure due to the weight of the air is the force that moves air into the lungs • At sea level, atmospheric pressure is 760 millimeters of mercury (mm Hg) • Moving the plunger of a syringe causes air to move in or out • Air movements in and out of the lungs occur in much the same way Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Air passageway Atmospheric pressure of 760 mm Hg on the outside Atmospheric pressure of 760 mm Hg on the inside Diaphragm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20 (a) (b) Inspiration • Intra-alveolar pressure decreases to about 758mm Hg as the thoracic cavity enlarges due to diaphragm downward movement caused by impulses carried by the phrenic nerves • Atmospheric pressure then forces air into the airways Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Atmospheric pressure (760 mm Hg) Intra-alveolar pressure (760 mm Hg) Intra-alveolar pressure (758 mm Hg) Diaphragm (a) (b) 21 Inspiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sternocleidomastoid elevates sternum Sternum moves Up and out Pectoralis minor elevates ribs External intercostal muscles pull ribs up and out Diaphragm contracts (a) Diaphragm contracts more (b) 22 23 Expiration • The forces responsible for normal resting expiration come from elastic recoil of lung tissues and from surface tension • These factors increase the intra-alveolar pressure about 1 mm Hg above atmospheric pressure forcing air out of the lungs 24 Expiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Posterior internal intercostal muscles pull ribs down and inward Diaphragm Diaphragm Abdominal organs recoil and press diaphragm upward Abdominal organs force diaphragm higher Abdominal wall muscles contract and compress abdominal organs (a) (b) 25 26 Respiratory Air Volumes and Capacities • Different degrees of effort in breathing move different volumes of air in and out of the lungs • This measurement of volumes is called spirometry Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lung volume in milliliters (mL) 6,000 5,000 Inspiratory reserve volume Vital capacity 4,000 Inspiratory capacity Total lung capacity 3,000 2,000 1,000 0 Tidal volume Residual volume Expiratory reserve volume Functional residual capacity 27 28 Alveolar Ventilation • The volume of new atmospheric air moved into the respiratory passages each minute is minute ventilation • It equals the tidal volume multiplied by the breathing rate • Much of the new air remains in the physiologic dead space • The tidal volume minus the physiologic dead space then multiplied by breathing rate is the alveolar ventilation rate • This is the volume of air that reaches the alveoli • This impacts the concentrations of oxygen and carbon dioxide in the alveoli 29 Nonrespiratory Air Movements • Air movements other than breathing are called nonrespiratory movements • They clear air passages, as in coughing and sneezing, or express emotions, as in laughing and crying 30 31 19.5: Control of Breathing • Normal breathing is a rhythmic, involuntary act that continues when a person is unconscious • Respiratory muscles can be controlled as well voluntarily 32 Respiratory Areas Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Groups of neurons in the brainstem comprise the respiratory areas that control breathing • Impulses travel on cranial nerves and spinal nerves, causing inspiration and expiration • Respiratory areas also adjust the rate and depth of breathing • The respiratory areas include: • Respiratory center of the medulla • Respiratory group of the pons Midbrain Fourth ventricle Pontine respiratory group Pons Medulla oblongata Ventral respiratory group Dorsal respiratory group Medullary respiratory center Internal (expiratory) intercostal muscles External (inspiratory) intercostal muscles Diaphragm 33 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Respiratory areas Pontine respiratory group Medullary respiratory center Ventral respiratory group Dorsal respiratory group Nerve impulses Nerve impulses Respiratory muscles Basic rhythm of breathing Forceful breathing 34 Factors Affecting Breathing • A number of factors affect breathing rate and depth including: • Partial pressure of oxygen (Po2) • Partial pressure of carbon dioxide (Pco2) • Degree of stretch of lung tissue • Emotional state • Level of physical activity • Receptors involved include mechanoreceptors and central and peripheral chemoreceptors Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Medulla oblongata Sensory nerve (branch of glossopharyngeal nerve) Carotid bodies Sensory nerve (branch of vagus nerve) Common carotid artery Aorta Aortic bodies Heart 35 Factors Affecting Breathing • Changes in blood pH, O2 and CO2 concentration stimulates chemoreceptors Sensory pathway • Motor impulses can travel Vagus nerve from the respiratory center to the diaphragm and external Phrenic nerve intercostal muscles • Contraction of these muscles Stretch receptors Lung causes the lungs to expand stimulating mechanoreceptors in the lungs • Inhibitory impulses from the mechanoreceptors back to the respiratory center prevent overinflation of the lungs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Respiratory center Spinal cord – – Motor pathways External intercostal muscles Intercostal nerve Rib Diaphragm 36 37 19.6: Alveolar Gas Exchanges • The alveoli are the sites of the vital process of gas exchange between the air and the blood 38 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Type I (squamous epithelial) cell of alveolar wall Type II (surfactantsecreting) cell Fluid with surfactant Macrophage Alveolus Respiratory membrane Cell of capillary wall Capillary lumen Alveolar fluid (with surfactant) Alveolar epithelium Alveolus Basement membrane of alveolar epithelium Interstitial space Respiratory membrane Basement membrane of capillary endothelium Capillary endothelium Diffusion of O2 Diffusion of CO2 Red blood cell Capillary 39 Respiratory Membrane • Part of the wall of an alveolus is made up of cells (type II cells) that secrete pulmonary surfactant • The bulk of the wall of an alveolus consists of a layer of simple squamous epithelium (type I cells) • Both of these layers make up the respiratory membrane through which gas exchange takes place 40 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. EP AS BM RBC AS IS 41 © Imagingbody.com Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Alveolus Diffusion of CO2 Alveolar wall PCO = 40 mm Hg 2 PCO = 45 mm Hg 2 PO = 104 mm Hg 2 Diffusion of O2 PO = 40 mm Hg 2 Blood flow (from body tissues) Blood flow (to body tissues) Capillary PCO = 40 mm Hg PO = 104 mm Hg 2 2 42 Diffusion Through the Respiratory Membrane • Molecules diffuse from regions where they are in higher concentration toward regions where they are in lower concentration • It is important to know the concentration gradient • In respiration, think in terms of gas partial pressures • Gases diffuse from areas of higher partial pressure to areas of lower partial pressure • The respiratory membrane is normally thin and gas exchange is rapid • Increased diffusion is favored with more surface area, shorter distance, greater solubility of gases and a steeper partial pressure gradient • Decreased diffusion occurs from decreased surface area 43 19.7: Gas Transport • Blood transports O2 and CO2 between the lungs and the body cells • As the gases enter the blood, they dissolve in the plasma or chemically combine with other atoms or molecules 44 Oxygen Transport • Almost all oxygen carried in the blood is bound to the protein hemoglobin in the form of oxyhemoglobin • Chemical bonds between O2 and hemoglobin are relatively unstable • Oxyhemoglobin releases O2 into the body cells • About 75% of the O2 remains bound to hemoglobin in the venous blood ensuring safe CO2 levels and thereby pH 45 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Alveolus Blood PO = 95 mm Hg Capillary Hemoglobin molecules 2 Alveolar wall Oxygen molecules Diffusion of oxygen (a) Hemoglobin molecules 2 Blood flow (to lungs) Oxyhemoglobin molecule Blood flow (from body tissues) Blood PO = 40 mm Hg Tissue cells Tissue PO = 40 mm Hg Diffusion of oxygen 2 (b) 46 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 100 % saturation of hemoglobin 90 80 70 60 50 40 30 20 10 0 10 20 30 40 50 60 70 80 PO2(mm Hg) 90 100 110 120 130 140 Oxyhemoglobin dissociation at 38°C 47 • The amount of oxygen released from oxyhemoglobin increases with: Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 100 80 70 PCO2 = 60 20 mm Hg 40 mm Hg 80 mm Hg 50 40 30 20 10 10 20 30 40 50 60 70 80 PO2 (mm Hg) 90 100 110 120 130 140 Oxyhemoglobin dissociation at 38°C Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 100 90 80 70 pH = 60 7.6 50 7.4 7.2 40 30 20 10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 0 10 20 30 40 50 60 70 80 90 100 PO2 (mm Hg) Oxyhemoglobin dissociation at 38°C 1 10 120 130 140 100 90 % saturation of hemoglobin 0 % saturation of hemoglobin % saturation of hemoglobin 90 80 70 60 50 40 30 20 10 0 10 20 30 40 50 60 70 80 PO2 (mm Hg) 90 48 100 110 120 Oxyhemoglobin dissociation at various temperatures 130 140 48 Carbon Dioxide Transport • Blood flowing through capillaries gains CO2 because the tissues have a high Pco2 • The CO2 is transported to the lungs in one of three forms: • As CO2 dissolved in plasma • As part of a compound with hemoglobin • As part of a bicarbonate ion 49 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tissue cell Tissue PCO2 = 45 mm Hg Cellular CO2 CO2 dissolved in plasma PCO = 40 mm Hg 2 Blood flow from systemic arteriole CO2 + H2O CO2 combined with hemoglobin to form carbaminohemoglobin HCO3- + H2CO3 PCO = 45 mm Hg H+ 2 H+combines with hemoglobin HCO3- Plasma Red blood cell Blood flow to systemic venule Capillary wall 50 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Capillary wall Cl- Red blood cell HCO3- Plasma Cl- HCO3HCO3Cl- 51 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Alveolus PCO = 40 mm Hg 2 CO2 CO2dissolved in plasma CO2 + H2O PCO = 45 mm Hg 2 Blood flow from pulmonary arteriole HCO3- Plasma CO2 Alveolar wall H2CO3 CO2 Carbaminohemoglobin PCO = 40 mm Hg 2 HCO3-+ H+ H+ released from hemoglobin Red blood cell CO2 + hemoglobin Blood flow to pulmonary venule Capillary wall 52 53 19.8: Lifespan Changes • Lifespan changes reflect an accumulation of environmental influences and the effects of aging in other organ systems, and may include: • The cilia become less active • Mucous thickening • Swallowing, gagging, and coughing reflexes slowing • Macrophages in the lungs lose efficiency • An increased susceptibility to respiratory infections • A “barrel chest” may develop • Bronchial walls thin and collapse • Dead space increasing 54