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The Respiratory System

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The Respiratory System

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  1. The Respiratory System 22

  2. The Respiratory System • Basic functions of the respiratory system • Supplies body with oxygen • Disposes of carbon dioxide • Four processes involved in respiration • Pulmonary ventilation • External respiration • Transport of respiratory gases • Internal respiration

  3. 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

  4. Nasal cavity Oral cavity Pharynx Nostril Left main (primary) bronchus Larynx Bronchi Trachea Carina of trachea Alveoli Right main (primary) bronchus Left lung Right lung Diaphragm Parietal pleura Organs of the Respiratory System Figure 22.1

  5. The Nose • Provides an airway for respiration • Moistens and warms air • Filters inhaled air • Resonating chamber for speech • Houses olfactory receptors

  6. 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

  7. Cribriform plate of ethmoid bone Frontal sinus Sphenoid sinus Nasal cavity Posterior nasal aperture Nasal conchae (superior, middle and inferior) Nasopharynx Pharyngeal tonsil Nasal meatuses (superior, middle, and inferior) Opening of pharyngotympanic tube Nasal vestibule Nostril Uvula Oropharynx Hard palate Palatine tonsil Soft palate Isthmus of the fauces Tongue Lingual tonsil Laryngopharynx Hyoid bone Larynx Epiglottis Vestibular fold Esophagus Thyroid cartilage Vocal fold Trachea Cricoid cartilage Thyroid gland (c) Illustration The Upper Respiratory Tract Figure 22.3c

  8. The Pharynx • Funnel-shaped passageway • Connects nasal cavity and mouth • Divided into three sections by location • Nasopharynx • Oropharynx • Laryngopharynx • Type of mucosal lining changes along its length

  9. 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 tube (auditory tube) • Tubal tonsil • Provides some protection from infection

  10. The Oropharynx • Arch-like entranceway—fauces • Extends from soft palate to the epiglottis • Epithelium • 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

  11. The Laryngopharynx • Passageway for both food and air • Epithelium • Stratified squamous epithelium • Continuous with the esophagus and larynx

  12. The Larynx • Three functions • Voice production • Provides an open airway • Routes air and food into the proper channels • Superior opening is • Closed during swallowing • Open during breathing

  13. Nine Cartilages of the Larynx • Thyroid cartilage • Shield-shaped, forms laryngeal prominence (Adam’s apple) • Three pairs of small cartilages • Arytenoid cartilages • Corniculate cartilages • Cuneiform cartilages • Epiglottis • Tips inferiorly during swallowing

  14. The Larynx • Vocal ligaments of the larynx • Vocal folds (true vocal cords) • Act in sound production • Vestibular folds (false vocal cords) • No role in sound production • Epithelium of the larynx • Stratified squamous—superior portion • Pseudostratified ciliated columnar—inferior portion

  15. Epiglottis Hyoid bone Thyrohyoid membrane Corniculate cartilage Arytenoid cartilage Thyroid cartilage Cricoid cartilage Glottis Tracheal cartilages (c) Photograph of cartilaginous framework of the larynx, posterior view Epiglottis Thyrohyoid membrane Body of hyoid bone Thyrohyoid membrane Cuneiform cartilage Fatty pad Vestibular fold (false vocal cord) Corniculate cartilage Arytenoid cartilage Thyroid cartilage Arytenoid muscle Vocal fold (true vocal cord) Cricoid cartilage Cricothyroid ligament Cricotracheal ligament Tracheal cartilages (d) Sagittal section (anterior on the right) Anatomy of the Larynx Figure 22.5c, d

  16. 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 Movements of the Vocal Folds Figure 22.6

  17. 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—straining • Innervation of the larynx • Recurrent laryngeal nerves (branch of vagus)

  18. The Trachea • Descends into the mediastinum • C-shaped cartilage rings keep airway open • Carina • Marks where trachea divides into two primary bronchi • Epithelium • Pseudostratified ciliated columnar

  19. Posterior Mucosa Pseudostratified ciliated columnar epithelium Lamina propria (connective tissue) Mucosa Submucosa Esophagus Submucosa Seromucous gland in submucosa Trachealis muscle Seromucous gland in submucosa Lumen of trachea Hyaline cartilage Hyaline cartilage Adventitia Anterior (a) Cross section of the trachea and esophagus (b) Photomicrograph of the tracheal wall (250) The Trachea Figure 22.7

  20. 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

  21. Superior lobe of right lung Trachea Superior lobe of left lung Left main (primary) bronchus Lobar (secondary) bronchus Segmental (tertiary) bronchus Inferior lobe of left lung Middle lobe of right lung Inferior lobe of right lung (a) The branching of the bronchial tree Bronchi in the Conducting Zone Figure 22.8a

  22. 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

  23. 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 • Airways widen with sympathetic stimulation • Airways constrict under parasympathetic direction

  24. Structures of the Respiratory Zone • Consists of air-exchanging structures • Respiratory bronchioles—branch from terminal bronchioles • Lead to alveolar ducts • Lead to alveolar sacs

  25. Alveoli Alveolar duct Respiratory bronchioles Alveolar duct Terminal bronchiole Alveolar sac (a) Structures of the Respiratory Zone Figure 22.9a

  26. Structures of the Respiratory Zone • Alveoli • ~300 million alveoli account for tremendous surface area of the lungs • Surface area of alveoli is ˜140 square meters

  27. Structures of the Respiratory Zone • Structure of alveoli • Type I cells—single layer of simple squamous epithelial cells • Surrounded by basal lamina • Alveolar and capillary walls plus their basal lamina form • Respiratory membrane

  28. Structures of the Respiratory Zone • Structures of alveoli (continued) • Type II cells—scattered among type I cells • Are cuboidal epithelial cells • Secrete surfactant • Reduces surface tension within alveoli • Alveolar macrophages

  29. Terminal bronchiole Respiratory bronchiole Smooth muscle Elastic fibers Alveolus Capillaries (a) Diagrammatic view of capillary-alveoli relationships Anatomy of Alveoli and the Respiratory Membrane Figure 22.10a, b

  30. Gross Anatomy of the Lungs • Major landmarks of the lungs • Apex, base, hilum, and root • Left lung • Superior and inferior lobes • Fissure—oblique • Right lung • Superior, middle, and inferior lobes • Fissures—oblique and horizontal

  31. Right lung Left lung Right superior lobe (3 segments) Left superior lobe (4 segments) Right middle lobe (2 segments) Right inferior lobe (5 segments) Left inferior lobe (5 segments) Bronchopulmonary Segments Figure 22.12

  32. 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

  33. Inspiration • Volume of thoracic cavity increases • Decreases internal gas pressure • Action of the diaphragm • Diaphragm flattens • Action of intercostal muscles • Contraction raises the ribs

  34. (a) Inspiration (b) Expiration Diaphragm and intercostal muscles contract (diaphragm descends and rib cage rises). Thoracic cavity volume increases. Inspiratory muscles relax (diaphragm rises and rib cage descends due to recoil of the costal cartilages). Thoracic cavity volume decreases. Ribs are elevated and sternum flares as external intercostals contract. Ribs and sternum are depressed as external intercostals relax. Changes in superior- inferior and anterior- posterior dimensions Diaphragm moves inferiorly during contraction. Diaphragm moves superiorly as it relaxes. Changes in lateral dimensions (superior view) External intercostals contract. External intercostals relax. Changes in Thoracic Volume Figure 22.14

  35. Trachea Thoracic wall At rest, no air movement: Air pressure in lungs is equal to atmospheric (air) pressure. Pressure in the pleural cavity is less than pressure in the lungs. This pressure difference keeps the lungs inflated. 1 Parietal pleura Pleural cavity Main bronchi Visceral pleura Lung Pleural cavity Thoracic wall Lung Diaphragm Air At rest 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. 2 V Expanded P V P Air flows in Air 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. 3 V V P P Air flows out Changes in Thoracic Volume Figure 22.15