Chapter 19 Respiratory System 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.

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

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

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 Soft palate Hard palate Pharynx Nostril Epiglottis Oral cavity Esophagus Larynx Trachea Bronchus 4 Right lung Left lung

Nose Superior Middle Frontal sinus Nasal conchae Inferior Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Superior Frontal sinus Middle Nasal conchae Inferior Sphenoidal sinus Nostril Pharyngeal tonsil Hard palate Nasopharynx Opening of auditory tube Uvula Tongue Palatine tonsil Oropharynx Lingual tonsil Epiglottis Hyoid bone Laryngopharynx Larynx Esophagus Trachea

b: © Biophoto Associates/Photo Researchers, Inc. Nasal Cavity Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mucus Particle Cilia Nasal cavity Goblet cell Epithelial cell (a) (b) b: © Biophoto Associates/Photo Researchers, Inc. pseudostratified columnar epithelium with cilia and goblet cells

Sinuses The sinuses are air-filled spaces in the maxillary, frontal, ethmoid, and sphenoid bones of the skull

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 Middle Frontal sinus Nasal conchae Inferior Sphenoidal sinus Nostril Pharyngeal tonsil Hard palate Nasopharynx Opening of auditory tube Uvula Palatine tonsil Tongue Oropharynx Lingual tonsil Epiglottis Hyoid bone Laryngopharynx Larynx Esophagus Trachea

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. Epiglottis Hyoid bone False vocal cord Thyroid cartilage Glottis Cricoid cartilage True vocal cord (a) Thyroid cartilage Hyoid bone Epiglottis Cuneiform cartilage Corniculate cartilage False vocal cord Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Arytenoid cartilage Thyroid cartilage Epiglottic cartilage True vocal cord Cricoid cartilage Hyoid bone (b) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Posterior portion of tongue Thyroid cartilage False vocal cord Cricoid cartilage Glottis True vocal cord Corniculate cartilage Cuneiform cartilage (a) Trachea (a) Epiglottis Glottis Inner lining of trachea Hyoid bone (b) Epiglottic cartilage Thyroid cartilage Cricoid cartilage Trachea (c) c: © CNRI/PhotoTake (b)

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 Cartilaginous ring Trachea Superior (upper) lobe bronchus Carina Left primary bronchus Right primary bronchus Superior (upper) lobe bronchus Inferior (lower) lobe bronchi Middle lobe bronchus 10

Connective tissue Smooth muscle Hyaline cartilage Ciliated epithelium 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 Connective tissue Smooth muscle Thyroid cartilage Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thyroid gland Cricoid cartilage Connective tissue Incision Smooth muscle Trachea Jugular notch Hyaline cartilage Ciliated epithelium Lumen of trachea © Ed Reschke

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 Left inferior (lower) lobe Right middle lobe Respiratory bronchiole Alveolar duct Alveolus 12

Branches of the Bronchial Tree Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The successive divisions of the branches from the trachea to the alveoli are: Right and left primary bronchi Secondary or lobar bronchi Tertiary or segmental bronchi Intralobular bronchioles Terminal bronchioles Respiratory bronchioles Alveolar ducts Alveolar sacs Alveoli © Ralph Hutchings/Visuals Unlimited

© McGraw-Hill Higher Education, Inc./Bob Coyle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood flow Blood flow Pulmonary venule Intralobular bronchiole Pulmonary arteriole Smooth muscle Blood flow 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 Capillary Alveoli Simple squamous epithelial cells Alveolus © McGraw-Hill Higher Education, Inc./Bob Coyle

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

Courtesy of the American Lung Association Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blood vessel Capillary Alveolus 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 Bronchiole Courtesy of the American Lung Association

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 Clavicle Trachea Plane of section Scapula Superior (upper) lobe of right lung Superior (upper) lobe of left lung Heart Visceral pleura Middle lobe of right lung Inferior (lower) lobe of left lung Pericardial cavity Parietal pleura Inferior (lower) lobe of right lung Pericardium Pleura Right pleural cavity Left pleural cavity Rib cartilage Sternum

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

Inspiration Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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 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. (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)

Inspiration Sternocleidomastoid elevates sternum Sternum moves 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 Diaphragm contracts more (a) (b)

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

Expiration Posterior internal intercostal muscles pull ribs down and 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)

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. 6,000 5,000 Inspiratory reserve volume Vital capacity Inspiratory capacity 4,000 Total lung capacity Lung volume in milliliters (mL) 3,000 2,000 Tidal volume Functional residual capacity 1,000 Expiratory reserve volume Residual volume

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

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

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

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

Medullary respiratory center 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

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

Factors Affecting Breathing Changes in blood pH, O2 and CO2 concentration stimulates chemoreceptors Motor impulses can travel from the respiratory center to the diaphragm and external intercostal muscles Contraction of these muscles 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 – – Sensory pathway Motor pathways Vagus nerve External intercostal muscles Phrenic nerve Intercostal nerve Stretch receptors Rib Lung Diaphragm

19.6: Alveolar Gas Exchanges The alveoli are the sites of the vital process of gas exchange between the air and the blood

Copyright © The McGraw-Hill Companies, Inc Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Type I (squamous epithelial) cell of alveolar wall Type II (surfactant- secreting) cell Fluid with surfactant Macrophage Alveolus Respiratory membrane Cell of capillary wall Capillary lumen Alveolar fluid (with surfactant) Alveolus Alveolar epithelium Basement membrane of alveolar epithelium Respiratory membrane Interstitial space Basement membrane of capillary endothelium Capillary endothelium Diffusion of O2 Diffusion of CO2 Red blood cell Capillary

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

Copyright © The McGraw-Hill Companies, Inc Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. EP AS BM RBC AS IS © Imagingbody.com

Alveolus Diffusion of CO2 Alveolar wall PCO2 = 40 mm Hg Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Alveolus Diffusion of CO2 Alveolar wall PCO2 = 40 mm Hg PO2 = 104 mm Hg PCO2 = 45 mm Hg PO2 = 40 mm Hg Diffusion of O2 Blood flow (from body tissues) Blood flow (to body tissues) Capillary PCO2 = 40 mm Hg PO2 = 104 mm Hg

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

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

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

Alveolus Blood PO = 95 mm Hg Capillary Hemoglobin molecules Blood Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Alveolus Blood PO = 95 mm Hg Capillary Hemoglobin molecules Blood PO = 40 mm Hg 2 2 Alveolar wall Oxygen molecules Blood flow (to lungs) Oxyhemoglobin molecule Diffusion of oxygen Blood flow (from body tissues) Tissue cells Tissue PO = 40 mm Hg Diffusion of oxygen 2 Hemoglobin molecules (a) (b)

% saturation of hemoglobin Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 100 90 80 70 60 % saturation of hemoglobin 50 40 30 20 10 10 20 30 40 50 60 70 80 90 100 1 10 120 130 140 PO2(mm Hg) Oxyhemoglobin dissociation at 38°C

The amount of oxygen released from oxyhemoglobin increases with: Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 100 90 80 70 60 PCO2 = 20 mm Hg % saturation of hemoglobin 50 40 mm Hg 40 80 mm Hg 30 20 10 10 20 30 40 50 60 70 80 90 100 1 10 120 130 140 PO2 (mm Hg) Oxyhemoglobin dissociation at 38°C Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 100 90 80 70 60 pH = 7.6 % saturation of hemoglobin 50 7.4 40 7.2 30 20 10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10 20 30 40 50 60 70 80 90 100 1 10 120 130 140 PO2 (mm Hg) 100 0°C Oxyhemoglobin dissociation at 38°C 90 10°C 80 20°C 70 30°C 38°C 60 43°C % saturation of hemoglobin 50 40 30 20 10 10 20 30 40 50 60 70 80 90 100 1 10 120 130 140 PO2 (mm Hg) 48 Oxyhemoglobin dissociation at various temperatures

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

Tissue cell Tissue PCO2 = 45 mm Hg Cellular CO2 CO2 dissolved 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 CO2 + H2O H2CO3 CO2 combined with hemoglobin to form carbaminohemoglobin PCO2 = 40 mm Hg HCO3- + H+ PCO2 = 45 mm Hg Blood flow from systemic arteriole Blood H+combines with hemoglobin flow to systemic HCO3- venule Plasma Red blood cell Capillary wall

Capillary wall Red blood cell Plasma Cl- HCO3- Cl- HCO3- HCO3- Cl- Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Capillary wall Red blood cell Plasma Cl- HCO3- Cl- HCO3- HCO3- Cl-

H+ released from hemoglobin Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Alveolus PCO2 = 40 mm Hg CO2 CO2 CO2 Alveolar wall CO2dissolved in plasma CO2 + H2O Carbaminohemoglobin PCO2 = 45 mm Hg H2CO3 PCO2 = 40 mm Hg HCO3-+ H+ Blood flow from pulmonary arteriole Blood flow to pulmonary venule HCO3- H+ released from hemoglobin CO2 + hemoglobin Plasma Red blood cell Capillary wall

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