C H A P T E R 22 The Respiratory System The Respiratory System Supplies body with oxygen Disposes of carbon dioxide Four processes in respiration Pulmonary ventilation External respiration Transport of respiratory gases Internal respiration Functional Anatomy of the Respiratory System Respiratory organs Nose, nasal cavity, and paranasal sinuses Pharynx, larynx, and trachea Bronchi and smaller branches Lungs and alveoli Divided into: Conducting zone Respiratory zone 1
Organs of the Respiratory System Trachea Carina of trachea Right main (primary) bronchus Right lung Parietal pleura Nasal cavity Nostril Larynx Oral cavity Pharynx Left main (primary) bronchus Bronchi Alveoli Left lung Diaphragm Figure 22.1 The Nose Provides an airway for respiration Moistens and warms air Filters inhaled air Resonating chamber for speech Houses olfactory receptors Size variation due to differences in nasal cartilages Skin is thin contains many sebaceous glands Frontal bone Nasal bone Septal cartilage Maxillary bone (frontal process) Lateral process of septal cartilage Minor alar cartilages Dense fibrous connective tissue Major alar cartilages (b) External skeletal framework Figure 22.2 The Nasal Cavity External nares nostrils Divided by nasal septum Continuous with nasopharynx Posterior nasal apertures choanae Figure 22.3c 2
Nasal Cavity Two types of mucous membrane Olfactory mucosa Near roof of nasal cavity Houses olfactory (smell) receptors Respiratory mucosa Lines nasal cavity Epithelium is pseudostratified ciliated columnar The Upper Respiratory Tract Cribriform plate of ethmoid bone Sphenoid sinus Posterior nasal aperture Nasopharynx Pharyngeal tonsil Opening of pharyngotympanic tube Uvula Oropharynx Palatine tonsil Isthmus of the fauces Laryngopharynx Esophagus Trachea (c) Illustration Larynx Epiglottis Vestibular fold Thyroid cartilage Vocal fold Cricoid cartilage Thyroid gland Frontal sinus Nasal cavity Nasal conchae (superior, middle and inferior) Nasal meatuses (superior, middle, and inferior) Nasal vestibule Nostril Hard palate Soft palate Tongue Lingual tonsil Hyoid bone Figure 22.3c Respiratory Mucosa Consists of: Pseudostratified ciliated columnar epithelium Goblet cells within epithelium Underlying layer of lamina propria Cilia move contaminated mucus posteriorly 3
Nasal Conchae Superior and middle part of the ethmoid bone Inferior a separate bone Project medially from the lateral wall of the nasal cavity Particulate matter deflected to mucus-coated surfaces Figure 22.3c The Paranasal Sinuses The Pharynx Funnel-shaped passageway Connects nasal cavity and mouth Divided into three locations Nasopharynx, oropharynx, and laryngopharynx Type of mucosal lining varies along its length Figure 22.3c 4
The Nasopharynx Superior to the point where food enters Only an air passageway Closed off during swallowing Pharyngeal tonsil (adenoids) Located on posterior wall Destroys entering pathogens Contains the opening to the pharyngotympanic (auditory) tube Epithelium is ciliated pseudostratfied columnar The Oropharynx Arch-like entranceway fauces Extends from soft palate to the epiglottis Epithelium is stratified squamous epithelium Two types of tonsils in the oropharynx Palatine tonsils in the lateral walls of the fauces Lingual tonsils covers the posterior surface of the tongue The Laryngopharynx Passageway for both food and air Lined with stratified squamous epithelium Continuous with the esophagus and larynx 5
The Larynx Three functions Voice production Provides an open airway Routes air and food into the proper channels Anatomy of the Larynx Figure 22.5a, b Movements of the Vocal Folds Anterior Thyroid cartilage Cricoid cartilage Vocal ligaments of vocal cords Glottis Lateral cricoarytenoid muscle Arytenoid cartilage Corniculate cartilage Posterior cricoarytenoid muscle Posterior Base of tongue Epiglottis Vestibular fold (false vocal cord) Vocal fold (true vocal cord) Glottis Inner lining of trachea Cuneiform cartilage Corniculate cartilage (a) Vocal folds in closed position; closed glottis (b) Vocal folds in open position; open glottis Figure 22.6 6
The Larynx Voice production Length of the vocal folds changes with pitch Loudness depends on the force of air across the vocal folds Sphincter function of the larynx Valsalva s maneuver Innervation of the larynx recurrent laryngeal nerves The Trachea Descends into the mediastinum Divides into two main bronchi C-shaped cartilage rings keep airway open The Trachea Mucosa Pseudostratified ciliated columnar epithelium Lamina propria (connective tissue) Submucosa Posterior Seromucous gland in submucosa Hyaline cartilage Mucosa Esophagus Submucosa (b) Photomicrograph of the tracheal wall (250 ) Trachealis Lumen of Seromucous gland muscle trachea in submucosa Hyaline cartilage Adventitia Anterior (a) Cross section of the trachea and esophagus Figure 22.7 7
Bronchi in the Conducting Zone Bronchial tree extensively branching respiratory passageways Primary bronchi (main bronchi) largest bronchi Right main bronchi wider and shorter than the left Figure 22.8a,b Bronchi in the Conducting Zone Secondary (lobar) bronchi Three on the right Two on the left Tertiary (segmental) bronchi Branch into each lung segment Bronchioles little bronchi, less than 1 mm in diameter Terminal bronchioles less than 0.5 mm in diameter Changes in Tissue Composition along Conducting Pathways Supportive connective tissues change C-shaped rings replaced by cartilage plates Epithelium changes First, pseudostratified ciliated columnar Replaced by simple columnar, then simple cuboidal epithelium Smooth muscle becomes important 8
The Respiratory Zone Consists of air-exchanging structures Respiratory bronchioles branch from terminal bronchioles Lead to alveolar ducts Lead to alveolar sacs Structures of the Respiratory Zone Figure 22.9a,b The Respiratory Zone Alveoli consist of type I cells and basal laminae Scattered among type I cells Cuboidal epithelial cells type II cells Secrete surfactant 9
Anatomy of Alveoli and the Respiratory Membrane Terminal bronchiole Respiratory bronchiole Smooth muscle Elastic fibers Alveolus Capillaries (a) Diagrammatic view of capillary-alveoli relationships Figure 22.10a, b Anatomy of Alveoli and the Respiratory Membrane Nucleus of type I (squamous epithelial) cell Alveolar pores Red blood cell Alveoli (gas-filled air spaces) Red blood cell in capillary Alveolus Type I cell of alveolar wall Type II (surfactantsecreting) cell Capillary O 2 Capillary CO 2 Macrophage Alveolus Endothelial cell nucleus Respiratory membrane (c) Detailed anatomy of the respiratory membrane Alveolar epithelium Fused basement membranes of the alveolar epithelium and the capillary endothelium Capillary endothelium Figure 22.10c The Respiratory Zone Features of alveoli Surrounded by elastic fibers Interconnect by way of alveolar pores Internal surfaces A site for free movement of alveolar macrophages 10
The Pleurae A double-layered sac surrounding each lung Parietal pleura Visceral pleura Pleural cavity Potential space between the visceral and parietal pleurae Pleurae help divide the thoracic cavity Central mediastinum Two lateral pleural compartments Diagram of the Pleurae and Pleural Cavities Gross Anatomy of the Lungs Anterior View of Thoracic Structures Figure 22.11a, b 11
Blood Supply and Innervation of the Lungs Pulmonary arteries deliver oxygen-poor blood to the lungs Pulmonary veins carry oxygenated blood to the heart Innervation Sympathetic, parasympathetic, and visceral sensory fibers Parasympathetic constrict airways Sympathetic dilate airways Transverse Cut through the Superior Thorax Vertebra Posterior Esophagus (in mediastinum) Root of lung at hilum Right lung Left main bronchus Left pulmonary Parietal pleura Visceral pleura Pleural cavity artery Left pulmonary vein Left lung Thoracic wall Pulmonary trunk Pericardial membranes Heart (in mediastinum) Anterior mediastinum Sternum Anterior (d) Transverse section through the thorax, viewed from above. Lungs, pleural membranes, and major organs in the mediastinum are shown. Figure 22.11d The Mechanisms of Ventilation Two phases of pulmonary ventilation Inspiration inhalation Expiration exhalation 12
Inspiration Volume of thoracic cavity increases Decreases internal gas pressure Action of the diaphragm diaphragm flattens Action of intercostal muscles contraction raises the ribs Deep inspiration requires Scalenes, sternocleidomastoid, and pectoralis minor Erector spinae extends the back Expiration Quiet expiration chiefly a passive process Inspiratory muscles relax Diaphragm moves superiorly Volume of thoracic cavity decreases Forced expiration an active process Produced by contraction of: The oblique and transversus abdominis muscles Location of Lungs in Thoracic Cavity Rib 8 9 Lung Clavicle Nipple Rib 3 4 5 6 Lung 10 7 11 12 (a) Posterior view Parietal pleura 8 Midaxillary line 9 10 Midclavicular line (b) Anterior view Infrasternal angle at the xiphisternal joint Costal margin Parietal pleura Figure 22.13 13
Changes in Thoracic Volume Changes in superiorinferior and anteriorposterior dimensionsi (a) Inspiration Diaphragm and intercostal muscles contract (diaphragm descends and rib cage rises). Thoracic cavity volume increases. Ribs are elevated and sternum flares as external intercostals contract. (b) Expiration Inspiratory muscles relax (diaphragm rises and rib cage descends due to recoil of the costal cartilages). Thoracic cavity volume decreases. Ribs and sternum are depressed as external intercostals relax. Diaphragm moves inferiorly during contraction. Diaphragm moves superiorly as it relaxes. Changes in lateral dimensions (superior view) External intercostals contract. External intercostals relax. Figure 22.14 Changes in Thoracic Volume 1 At rest, no air Trachea movement: Air pressure in lungs is Main bronchi equal to atmospheric (air) pressure. Pressure Lung in the pleural cavity is less than pressure in the lungs. This pressure difference keeps the lungs inflated. Diaphragm Air 2 Inspiration: Inspiratory muscles contract and increase the volume of the thoracic and pleural cavities. Pleural fluid in the pleural cavity holds the parietal and visceral pleura close together, causing the lungs to expand. As volume increases, pressure decreases and air flows into the lungs. Air 3 Expiration: Inspiratory muscles relax, reducing thoracic volume, and the lungs recoil. Simultaneously, volumes of the pleural cavity and the lungs decrease, causing pressure to increase in the lungs, and air flows out. Resting state is reestablished. Thoracic wall Pleural cavity At rest Expanded Lung Parietal pleura Visceral pleura V P Air flows in V P Air flows out Pleural Thoracic cavity wall V P V P Figure 22.15 How The Lungs Work 14
Location of Peripheral Chemoreceptors Brain Sensory nerve fiber in cranial nerve IX (pharyngeal branch of glossopharyngeal) External carotid artery Internal carotid artery Carotid body Common carotid artery Cranial nerve X (vagus nerve) Sensory nerve fiber in cranial nerve X Aortic bodies in aortic arch Aorta Heart Figure 22.17 Disorders of Lower Respiratory Structures Bronchial asthma a type of allergic inflammation A hypersensitivity to irritants in the air or to stress Asthma attacks characterized by: Contraction of bronchiole smooth muscle Secretion of mucus in airways Disorders of Lower Respiratory Structures Chronic obstructive pulmonary disease (COPD) Airflow into and out of the lungs is difficult Obstructive emphysema Chronic bronchitis History of smoking 15
Disorders of Lower Respiratory Structures Figure 22.18 Alveolar Changes in Emphysema Figure 22.19 Disorders of Lower Respiratory Structures Cystic fibrosis (CF) inherited disease Exocrine gland function is disrupted Respiratory system affected by: Oversecretion of viscous mucus 16
Disorders of Upper Respiratory Structures Epistaxis nosebleed Epiglottitis inflammation and swelling of the epiglottis 17