Chapter 22A Respiratory System: Slides by Barbara Heard and W. Rose. figures from Marieb & Hoehn 9th ed. Portions copyright Pearson Education Respiratory System Functions • Respiration • Supply O2, dispose of CO2 • Four processes (next slide) • Involves circulatory system • Olfaction • Speech Processes of Respiration • Pulmonary ventilation (breathing): moving air into and out of lungs • External respiration: O2 and CO2 exchange between lungs and blood • Transport: O2 and CO2 in blood • Internal respiration: O2 and CO2 exchange between systemic blood vessels and tissues © 2013 Pearson Education, Inc. Respiratory system Circulatory system Respiratory System: Functional Anatomy • Major organs – Nose, nasal cavity, and paranasal sinuses – Pharynx – Larynx – Trachea – Bronchi and their branches – Lungs and alveoli © 2013 Pearson Education, Inc. Figure 22.1 Major respiratory organs and surrounding structures Nasal cavity Oral cavity Nostril Pharynx Larynx Trachea Carina of trachea Right main (primary) bronchus Right lung Left main (primary) bronchus Left lung Diaphragm © 2013 Pearson Education, Inc. Functional Anatomy • Respiratory zone-site of gas exchange – Microscopic structures-respiratory bronchioles, alveolar ducts, and alveoli • Conducting zone-conduits to gas exchange sites – Includes all other respiratory structures; cleanses, warms, humidifies air • Diaphragm and other respiratory muscles promote ventilation PLAY Animation: Rotating face © 2013 Pearson Education, Inc. Nose – Provides an airway for respiration – Moistens and warms entering air – Filters and cleans inspired air – Serves as resonating chamber for speech – Houses olfactory receptors © 2013 Pearson Education, Inc. Figure 22.2b The external nose. Frontal bone Nasal bone Septal cartilage Maxillary bone (frontal process) Nasal cartilages Dense fibrous connective tissue Nares (nostrils) External skeletal framework © 2013 Pearson Education, Inc. Nasal cavity • • • • Divided by midline nasal septum Opens into nasopharynx posteriorly Roof: ethmoid and sphenoid bones Lateral walls: ethmoid, inferior conchae, palatine bones • Floor: hard palate (maxilla & palatine bones), soft palate (muscle) • Lined with mucous membranes – Olfactory mucosa – Respiratory mucosa: ciliated; cilia sweep mucus toward pharynx © 2013 Pearson Education, Inc. Frontal sinus Superior, middle, and inferior meatus Superior nasal concha Ethmoid Middle bone nasal concha Sphenoid sinus Nasal bone Inferior nasal concha Maxillary bone Palatine bone Nasal cavity: left lateral wall Nasal septum removed. Copyright © 2010 Pearson Education, Inc. Frontal sinus Nasal bone Sphenoid sinus Perpendicular plate of ethmoid bone Septal cartilage Hard Palatine bone palate Maxilla Vomer Nasal cavity: midline structures Septum in place. Note ethmoid bone, vomer, septal cartilage. Copyright © 2010 Pearson Education, Inc. Figure 22.3b The upper respiratory tract. Cribriform plate of ethmoid bone Sphenoid sinus Frontal sinus Nasal cavity Nasal conchae (superior, middle and inferior) Nasal meatuses (superior, middle, and inferior) Nasal vestibule Posterior nasal aperture Nasopharynx Pharyngeal tonsil Opening of pharyngotympanic tube Uvula Nostril Oropharynx Palatine tonsil Isthmus of the fauces Hard palate Soft palate Tongue Lingual tonsil Laryngopharynx Esophagus Larynx Epiglottis Vestibular fold Thyroid cartilage Vocal fold Cricoid cartilage Trachea Thyroid gland Illustration © 2013 Pearson Education, Inc. Hyoid bone Figure 22.3a The upper respiratory tract. Olfactory nerves Olfactory epithelium Superior nasal concha and superior nasal meatus Mucosa of pharynx Middle nasal concha and middle nasal meatus Tubal tonsil Inferior nasal concha and inferior nasal meatus Pharyngotympanic (auditory) tube Nasopharynx Hard palate Soft palate Uvula Photograph © 2013 Pearson Education, Inc. Nasal Cavity • Nasal conchae-superior, middle, and inferior – Protrude medially from lateral walls – Increase mucosal area – Enhance air turbulence • Nasal meatus – Groove inferior to each concha © 2013 Pearson Education, Inc. Functions of the Nasal Mucosa and Conchae • During inhalation: filter, heat, moisten air • During exhalation: reclaim heat, moisture © 2013 Pearson Education, Inc. Paranasal Sinuses • In frontal, sphenoid, ethmoid, and maxillary bones • Lighten skull; secrete mucus; help to warm and moisten air © 2013 Pearson Education, Inc. Homeostatic Imbalance • Rhinitis – Inflammation of nasal mucosa – Nasal mucosa continuous with mucosa of respiratory tract spreads from nose throat chest – Spreads to tear ducts and paranasal sinuses causing • Blocked sinus passageways air absorbed vacuum sinus headache © 2013 Pearson Education, Inc. Upper respiratory tract Pharynx Nasopharynx Oropharynx Laryngopharynx Regions of the pharynx © 2013 Pearson Education, Inc. Nasopharynx • Air passageway posterior to nasal cavity • Lining - pseudostratified columnar epithelium • Soft palate and uvula close nasopharynx during swallowing • Pharyngeal tonsil (adenoids) on posterior wall • Pharyngotympanic (auditory) tubes drain and equalize pressure in middle ear; open into lateral walls © 2013 Pearson Education, Inc. Oropharynx • Passageway for food and air from level of soft palate to epiglottis • Lining of stratified squamous epithelium • Palatine tonsils-in lateral walls of fauces • Lingual tonsil-on posterior surface of tongue © 2013 Pearson Education, Inc. Laryngopharynx • Passageway for food and air • Posterior to upright epiglottis • Extends to larynx, where continuous with esophagus • Lined with stratified squamous epithelium © 2013 Pearson Education, Inc. Figure 22.3b The upper respiratory tract. Cribriform plate of ethmoid bone Sphenoid sinus Frontal sinus Nasal cavity Nasal conchae (superior, middle and inferior) Nasal meatuses (superior, middle, and inferior) Nasal vestibule Posterior nasal aperture Nasopharynx Pharyngeal tonsil Opening of pharyngotympanic tube Uvula Nostril Oropharynx Palatine tonsil Isthmus of the fauces Hard palate Soft palate Tongue Lingual tonsil Laryngopharynx Esophagus Larynx Epiglottis Vestibular fold Thyroid cartilage Vocal fold Cricoid cartilage Trachea Thyroid gland Illustration © 2013 Pearson Education, Inc. Hyoid bone Larynx • Structures through which air passes, between laryngopharynx and trachea • Provides patent airway • Routes air and food into proper channels • Voice production © 2013 Pearson Education, Inc. Larynx • Thyroid cartilage (laryngeal prominence = Adam's apple) • Cricoid cartilage ring-shaped • Other cartilages • Epiglottis (elastic cartilage); covers laryngeal inlet during swallowing to prevent food/water from entering larynx © 2013 Pearson Education, Inc. Larynx Epiglottis Hyoid bone Thyroid cartilage Laryngeal prominence (Adam’s apple) Cricoid cartilage Tracheal cartilages Anterior superficial view Larynx Hyoid bone Epiglottis Vestibular fold (false vocal cord) Thyroid cartilage Vocal fold (true vocal cord) Cricoid cartilage Tracheal cartilages Sagittal view; anterior surface to the right © 2013 Pearson Education, Inc. Larynx • Vocal ligaments – Contain elastic fibers – Form core of vocal folds (true vocal cords) • Glottis-opening between vocal folds • Folds vibrate to produce sound as air rushes up from lungs • Vestibular folds (false vocal cords) – Superior to vocal folds – No part in sound production – Help to close glottis during swallowing © 2013 Pearson Education, Inc. Figure 22.5. Vocal fold movements. Base of tongue Epiglottis Vestibular fold (false vocal cord) Vocal fold (true vocal cord) Glottis Lumen of trachea Vocal folds in closed position; closed glottis © 2013 Pearson Education, Inc. Vocal folds in open position; open glottis Voice Production • Intermittent release of expired air while opening and closing glottis • Pitch determined by length and tension of vocal cords • Loudness depends upon force of air • Chambers of pharynx, oral, nasal, and sinus cavities amplify and enhance sound quality • Sound is "shaped" into language by muscles of pharynx, tongue, soft palate, lips © 2013 Pearson Education, Inc. Larynx • Vocal folds can act as sphincter to prevent air passage • Example: Valsalva's maneuver – Glottis closes to prevent exhalation – Abdominal muscles contract – Intra-abdominal pressure rises – Helps to stabilizes trunk during heavy lifting; helps to empty bladder or bowel © 2013 Pearson Education, Inc. Trachea • Air passageway from larynx into mediastinum; “windpipe” • Wall composed of three layers – Mucosa-ciliated pseudostratified epithelium with goblet cells – Submucosa – Adventitia-outermost layer made of connective tissue; encases C-shaped rings of hyaline cartilage • Carina – where trachea branches into two main bronchi © 2013 Pearson Education, Inc. Trachea Posterior Mucosa Esophagus Trachealis muscle Submucosa Lumen of trachea Seromucous gland in submucosa Hyaline cartilage Adventitia Anterior Cross section of trachea and esophagus © 2013 Pearson Education, Inc. Bronchi and Subdivisions • Bronchial (respiratory) tree: Air passages undergo ~23 orders of branching • Conducting zone • Respiratory zone © 2013 Pearson Education, Inc. Conducting Zone Structures • Trachea • Right and left main bronchi – Each main bronchus enters hilum of one lung – Right main bronchus wider, shorter, more vertical than left • Lobar bronchi – One to each lobe of each lung: 3 right, 2 left • Segmental bronchi • Smaller and smaller branches – Bronchioles < 1 mm in diameter – Terminal bronchioles < 0.5 mm diameter © 2013 Pearson Education, Inc. Figure 22.7 Conducting zone passages. Trachea Superior lobe of left lung Left main (primary) bronchus Superior lobe of right lung Lobar (secondary) bronchus Segmental (tertiary) bronchus Middle lobe of right lung Inferior lobe of right lung © 2013 Pearson Education, Inc. Inferior lobe of left lung Conducting Zone Structures • From bronchi through bronchioles, structural changes occur – Cartilage rings gradually disappear – Elastic fibers replace cartilage in bronchioles – Epithelium changes from pseudostratified columnar to cuboidal – Cilia, goblet cells become sparse – Relative amount of smooth muscle increases • Allows constriction © 2013 Pearson Education, Inc. Respiratory Zone • • • • • Where gas exchange takes place Begins at ends of terminal bronchioles Respiratory bronchioles Alveolar ducts Alveolar sacs – Alveolar sacs contain clusters of alveoli – ~300 million alveoli make up most of lung volume – Sites of gas exchange © 2013 Pearson Education, Inc. Figure 22.8a Respiratory zone structures. Alveoli Alveolar duct Respiratory bronchioles Terminal bronchiole © 2013 Pearson Education, Inc. Alveolar duct Alveolar sac Figure 22.8b Respiratory zone structures. Respiratory bronchiole Alveolar duct Alveoli Alveolar sac © 2013 Pearson Education, Inc. Alveolar pores Respiratory Membrane • Alveolar and capillary walls and their fused basement membranes – ~0.5-µm-thick; gas exchange across membrane by simple diffusion • Alveolar walls – Single layer of squamous epithelium (type I alveolar cells) • Scattered cuboidal type II alveolar cells secrete surfactant and antimicrobial proteins © 2013 Pearson Education, Inc. Figure 22.9a Alveoli and the respiratory membrane. Terminal bronchiole Respiratory bronchiole Smooth muscle Elastic fibers Alveolus Capillaries Diagrammatic view of capillary-alveoli relationships © 2013 Pearson Education, Inc. Alveoli • Surrounded by fine elastic fibers and pulmonary capillaries • Alveolar pores connect adjacent alveoli • Equalize air pressure throughout lung • Alveolar macrophages keep alveolar surfaces “clean” – 2 million dead macrophages/hour carried by cilia throat swallowed © 2013 Pearson Education, Inc. Figure 22.9c Alveoli and the respiratory membrane. Red blood cell Nucleus of type I alveolar cell Alveolar pores Capillary Capillary Macrophage Endothelial cell nucleus Alveolus Respiratory membrane Alveoli (gas-filled air spaces) Red blood cell in capillary Type II alveolar cell Type I alveolar cell Detailed anatomy of the respiratory membrane © 2013 Pearson Education, Inc. Alveolus Alveolar epithelium Fused basement membranes of alveolar epithelium and capillary endothelium Capillary endothelium Lungs • Composed primarily of alveoli • Elastic connective tissue • Apex (superior), base (rests on diaphragm) • Root (hilum): site of entry/exit of blood vessels, bronchi, lymphatics, nerves • Left lung smaller than right – Cardiac notch-concavity for heart – Superior, inferior lobes • Right lung – Superior, middle, inferior lobes © 2013 Pearson Education, Inc. Figure 22.10c Anatomical relationships of organs in the thoracic cavity. Vertebra Right lung Parietal pleura Visceral pleura Pleural cavity Posterior Esophagus (in mediastinum) Root of lung at hilum • Left main bronchus • Left pulmonary artery • Left pulmonary vein Left lung Thoracic wall Pulmonary trunk Pericardial membranes Sternum Heart (in mediastinum) Anterior mediastinum Anterior Transverse section through the thorax, viewed from above. Lungs, pleural membranes, and major organs in the mediastinum are shown. © 2013 Pearson Education, Inc. Figure 22.10a. Organs in the thoracic cavity. Intercostal muscle Rib Lung Parietal pleura Pleural cavity Visceral pleura Trachea Thymus Apex of lung Left superior lobe Right superior lobe Horizontal fissure Right middle lobe Oblique fissure Oblique fissure Left inferior lobe Right inferior lobe Heart (in mediastinum) Diaphragm Cardiac notch Base of lung Anterior view. The lungs flank mediastinal structures laterally. © 2013 Pearson Education, Inc. Figure 22.10b Anatomical relationships of organs in the thoracic cavity. Apex of lung Pulmonary artery Left superior lobe Oblique fissure Pulmonary vein Left inferior lobe Cardiac impression Hilum of lung Oblique fissure Aortic impression © 2013 Pearson Education, Inc. Left main bronchus Lobules Photograph of medial view of the left lung. Figure 22.11 A cast of the bronchial tree. Right lung Right superior lobe (3 segments) Left lung Left superior lobe (4 segments) Right middle lobe (2 segments) Right inferior lobe (5 segments) © 2013 Pearson Education, Inc. Left inferior lobe (5 segments) Pulmonary circulation • Low pressure, low resistance • Pulmonary arteries deliver systemic venous blood to lungs for oxygenation • Pulmonary veins carry oxygenated blood from respiratory zones to heart • Pulmonary capillary endothelium contains angiotensin-converting enzyme – Converts angiotensin I to angiotensin II. (Renin converts angiotensinogen to Ang I.) © 2013 Pearson Education, Inc. Bronchial circulation • Oxygenated blood for lung tissue • Only circulatory pathway that goes from systemic arteries to pulmonary veins © 2013 Pearson Education, Inc. Pleurae • Thin, double-layered serosa • Parietal pleura on thoracic wall, superior face of diaphragm, around heart, between lungs • Visceral pleura on external lung surface • Pleural fluid fills thin pleural cavity – Provides lubrication and surface tension assists in expansion and recoil © 2013 Pearson Education, Inc. Figure 22.10c Organs in the thoracic cavity Vertebra Right lung Parietal pleura Visceral pleura Pleural cavity Posterior Esophagus (in mediastinum) Root of lung at hilum • Left main bronchus • Left pulmonary artery • Left pulmonary vein Left lung Thoracic wall Pulmonary trunk Pericardial membranes Sternum Heart (in mediastinum) Anterior mediastinum Anterior Transverse section through the thorax, viewed from above. Lungs, pleural membranes, and major organs in the mediastinum are shown. © 2013 Pearson Education, Inc. Mechanics of Breathing • Pulmonary ventilation consists of two phases – Inspiration-gases flow into lungs – Expiration-gases exit lungs © 2013 Pearson Education, Inc. Pressure Relationships in the Thoracic Cavity • Atmospheric pressure (Patm) – Pressure exerted by air surrounding body – 760 mm Hg at sea level = 1 atmosphere • Respiratory pressures described relative to Patm – Negative respiratory pressure-less than Patm – Positive respiratory pressure-greater than Patm – Zero respiratory pressure = Patm © 2013 Pearson Education, Inc. Intrapulmonary Pressure • Intrapulmonary (intra-alveolar) pressure (Ppul) – Pressure in alveoli – Fluctuates with breathing – Always eventually equalizes with Patm © 2013 Pearson Education, Inc. Intrapleural Pressure • Intrapleural pressure (Pip) – Pressure in pleural cavity – Fluctuates with breathing – Always a negative pressure (<Patm and <Ppul) – Fluid level must be minimal • Pumped out by lymphatics • If accumulates positive Pip pressure lung collapse © 2013 Pearson Education, Inc. Intrapleural Pressure • Negative Pip caused by opposing forces – Two inward forces promote lung collapse • Elastic recoil of lungs decreases lung size • Surface tension of alveolar fluid reduces alveolar size – One outward force tends to enlarge lungs • Elasticity of chest wall pulls thorax outward © 2013 Pearson Education, Inc. Pressure Relationships • If Pip = Ppul or Patm lungs collapse • (Ppul – Pip) = transpulmonary pressure – Keeps airways open – Greater transpulmonary pressure larger lungs © 2013 Pearson Education, Inc. Figure 22.12 Intrapulmonary and intrapleural pressure relationships. Atmospheric pressure (Patm) 0 mm Hg (760 mm Hg) Parietal pleura Thoracic wall Visceral pleura Pleural cavity Transpulmonary pressure 4 mm Hg (the difference between 0 mm Hg and −4 mm Hg) –4 0 Lung Diaphragm © 2013 Pearson Education, Inc. Intrapulmonary pressure (Ppul) 0 mm Hg (760 mm Hg) Intrapleural pressure (Pip) −4 mm Hg (756 mm Hg) Homeostatic Imbalance • Atelectasis (lung collapse) due to – Plugged bronchioles collapse of alveoli – Pneumothorax-air in pleural cavity • From either wound in parietal or rupture of visceral pleura • Treated by removing air with chest tubes; pleurae heal lung reinflates © 2013 Pearson Education, Inc. Pulmonary Ventilation • Inspiration and expiration • Mechanical processes that depend on volume changes in thoracic cavity – Volume changes pressure changes – Pressure changes gases flow to equalize pressure © 2013 Pearson Education, Inc. Boyle's Law • Relationship between pressure and volume of a gas – Gases fill container; if container size reduced increased pressure • Pressure (P) varies inversely with volume (V): – P1V1 = P2V2 © 2013 Pearson Education, Inc. Inspiration • Active process – Inspiratory muscles (diaphragm and external intercostals) contract – Thoracic volume increases intrapulmonary pressure drops (to 1 mm Hg) – Lungs stretched and intrapulmonary volume increases – Air flows into lungs, down its pressure gradient, until Ppul = Patm © 2013 Pearson Education, Inc. Forced Inspiration • Vigorous exercise, COPD accessory muscles (scalenes, sternocleidomastoid, pectoralis minor) further increase in thoracic cage size © 2013 Pearson Education, Inc. Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (1 of 2) Slide 1 Sequence of events Changes in anterior-posterior and superior-inferior dimensions Changes in lateral dimensions (superior view) 1 Inspiratory muscles contract (diaphragm descends; rib cage rises). Inspiration 2 Thoracic cavity volume increases. 3 Lungs are stretched; intrapulmonary volume increases. Ribs are elevated and sternum flares as external intercostals contract. External intercostals contract. 4 Intrapulmonary pressure drops (to –1 mm Hg). 5 Air (gases) flows into lungs down its pressure gradient until intrapulmonary pressure is 0 (equal to atmospheric pressure). © 2013 Pearson Education, Inc. Diaphragm moves inferiorly during contraction. Expiration • Quiet expiration normally passive process – Inspiratory muscles relax – Thoracic cavity volume decreases – Elastic lungs recoil and intrapulmonary volume decreases pressure increases (Ppul rises to +1 mm Hg) – Air flows out of lungs down its pressure gradient until Ppul = 0 • Note: forced expiration-active process; uses abdominal (oblique and transverse) and internal intercostal muscles © 2013 Pearson Education, Inc. Figure 22.13 Changes in thoracic volume and sequence of events during inspiration and expiration. (2 of 2) Slide 1 Sequence of events Changes in anterior-posterior and superior-inferior dimensions Changes in lateral dimensions (superior view) 1 Inspiratory muscles relax (diaphragm rises; rib cage descends due to recoil of costal cartilages). Expiration 2 Thoracic cavity volume decreases. 3 Elastic lungs recoil passively; intrapulmonary Volume decreases. Ribs and sternum are depressed as external intercostals relax. External intercostals relax. 4 Intrapulmonary pressure rises (to +1 mm Hg). 5 Air (gases) flows out of lungs down its pressure gradient until intrapulmonary pressure is 0. © 2013 Pearson Education, Inc. Diaphragm moves superiorly as it relaxes. Intrapleural pressure. Pleural cavity pressure becomes more negative as chest wall expands during inspiration. Returns to initial value as chest wall recoils. Volume of breath. During each breath, the pressure gradients move 0.5 liter of air into and out of the lungs. Volume (L) Intrapulmonary pressure. Pressure inside lung decreases as lung volume increases during inspiration; pressure increases during expiration. Pressure relative to atmospheric pressure (mm Hg) Figure 22.14 Changes in intrapulmonary and intrapleural pressures during inspiration and expiration. Inspiration Expiration Intrapulmonary pressure +2 0 –2 –4 Transpulmonary pressure –6 Intrapleural pressure –8 Volume of breath 0.5 0 5 seconds elapsed © 2013 Pearson Education, Inc. Physical Factors Influencing Pulmonary Ventilation • Three physical factors influence the ease of air passage and the amount of energy required for ventilation. – Airway resistance – Alveolar surface tension – Lung compliance © 2013 Pearson Education, Inc. Airway Resistance • Friction-major nonelastic source of resistance to gas flow; occurs in airways • Relationship between flow (F), pressure (P), and resistance (R) is: – ∆P - pressure gradient between atmosphere and alveoli (2 mm Hg or less during normal quiet breathing) – Gas flow changes inversely with resistance © 2013 Pearson Education, Inc. Airway Resistance • Resistance usually insignificant – Large airway diameters in first part of conducting zone – Progressive branching of airways as get smaller, increasing total cross-sectional area – Resistance greatest in medium-sized bronchi • Resistance disappears at terminal bronchioles where diffusion drives gas movement © 2013 Pearson Education, Inc. Figure 22.15 Resistance in respiratory passageways. Conducting zone Respiratory zone Resistance Medium-sized bronchi Terminal bronchioles 1 © 2013 Pearson Education, Inc. 5 10 15 Airway generation (stage of branching) 20 23 Homeostatic Imbalance • As airway resistance rises, breathing movements become more strenuous • Severe constriction or obstruction of bronchioles – Can prevent life-sustaining ventilation – Can occur during acute asthma attacks; stops ventilation • Epinephrine dilates bronchioles, reduces air resistance © 2013 Pearson Education, Inc. Alveolar Surface Tension • Surface tension – Attraction of liquid molecules for one another at gas-liquid interface – Resists any force that tends to increase surface area of liquid – Water has high surface tension – Water layer on alveolar walls generates a “shrinking” (closing) force © 2013 Pearson Education, Inc. Alveolar Surface Tension • Surfactant – Anything that reduces surface tension – Type II alveolar cells make surfactant (lipd/protein mix) – Reduces surface tension of alveolar fluid and discourages alveolar collapse – Insufficient quantity in premature infants causes infant respiratory distress syndrome © 2013 Pearson Education, Inc. Lung Compliance • Compliance = ΔV / ΔP • ΔV = change in lung volume • ΔP = change in transpulmonary pressure Volume (mL) 2500 2000 1500 1000 500 0 © 2013 Pearson Education, Inc. 2 4 6 Pressure (mmHg) 8 Lung Compliance • High lung compliance easy to expand lungs • Normally high, due to – Lung tissue that is easy to distend (stretch) – Surfactant, which decreases alveolar surface tension • Diminished by – Scar tissue (which is inelastic) replacing lung tissue (fibrosis) – Reduced production of surfactant – Decreased flexibility of thoracic cage © 2013 Pearson Education, Inc. Lung Compliance • Lung compliance is also influenced by compliance of the thoracic wall, which is decreased by: – Deformities of thorax – Ossification of costal cartilage – Paralysis of intercostal muscles © 2013 Pearson Education, Inc.