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Respiratory System: Functions, Divisions, and Histology

This article provides an overview of the functions, subdivisions, and histology of the respiratory system. It covers the extrapulmonary and intrapulmonary portions, as well as the conducting and respiratory portions.

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Respiratory System: Functions, Divisions, and Histology

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  1. Respiratory System Dr. Jack L. Haar

  2. Functions of Respiratory System • Transport air to and from lungs • Maintains airway patency • Regulates air temperature • Humidifies air • Decreases air velocity • Cleanses air • Gaseous exchange • Olfaction • Phonation

  3. MAJOR SUBDIVISIONS – Extrapulmonary portion – Intrapulmonary portion

  4. Extrapulmonary portion 1. Nasal cavity Nasal 2. Pharynx Oral Laryngeal 3. Larynx 4. Trachea 5. Primary bronchi

  5. Extrapulmonaryportion 1. Nasal cavity Nasal 2. Pharynx Oral Laryngeal 3. Larynx 4. Trachea 5. Primary bronchi

  6. MAJOR SUBDIVISIONS – Extrapulmonary portion – Intrapulmonary portion

  7. Intrapulmonaryportion Secondary bronchi Larynx Trachea 1. Secondary bronchi 2. Bronchioles (and terminal bronchioles) 3. Respiratory bronchioles 4. Alveolar ducts 5. Alveoli

  8. Intrapulmonary portion 1. Secondary bronchi 2. Bronchioles (and terminal bronchioles) 3. Respiratory bronchioles 4. Alveolar ducts 5. Alveoli

  9. Classification by function: Conducting portion 1. Nasal cavity 2. Pharynx 3. Larynx 4. Trachea 5. Primary bronchi 6. Secondary bronchi 7. Bronchioles (and terminal bronchioles)

  10. Classification by function: Respiratory portion 1. Respiratory bronchioles 2. Alveolar ducts 3. Alveolar sacs 4. Alveoli Terminal bronchiole RB AS RB AD Alveoli

  11. Histology overview of respiratory passageways • Mucosa: epithelium, lamina propria and muscularis mucosa • Epithelium: pseudostratified columnar epithelium with cilia and goblet cells = Respiratory epithelium

  12. Layers of “typical” conducting passageway • Lamina propria • Vascularized • Longitudial arranged elastic fibers • Deepest layer • Elastic lamina OR • Muscularis mucosae OR • Neither

  13. Submucosa – connective tissue layer; contains mixed (mucous and serous secreting glands in larger passageways)Bone or Cartilage – present to level of bronchioles where it drops outAdventitia - connective tissue

  14. TRANSITIONS – Layers become thinner and drop out – Epithelium -decreases in height - goblet cells drop out - cilia disappear – Mixed glands drop out – Cartilage drops out

  15. Wall of alveolus where gas exchange occurs Alveolus (Inter)alveolar Septum Simple squamous epithelium Connective tissue core Reticular + elastic fibers and CT cells Capillaries Alveolus Cap Simple squamous epithelium

  16. Variation on this layering theme

  17. MAJOR SUBDIVISIONS – Conducting portion – Respiratory portion Conducts air from exterior to where gas can be exchanged, i.e., alveoli

  18. Extrapulmonary of Conducting Portion • Nasal cavities • Non-olfactory region • Vestibules – transition from skin to respiratory epithelium • Nasal fossae • Respiratory epithelium, • Abundant blood vessels • Muscularis mucosae absent • Bones and cartilage for patiency Non-olfactory region

  19. Nasal cavity Non-olfactory region Resp. epith. Lam. propria Submucosa (some cartilage) Bone NO musc. muc.

  20. Nasal cavity Olfactory region

  21. Olfactory region U-shaped area in posterior, superior regions of nasal fossae Superior concha Non-olfactory region Olfactory region

  22. Nasal cavity Olfactory mucosa “Typical” nasal mucosa

  23. Olfactory cells: bipolar neurons, single dendrite extends to surface terminates in olfactory vesicle, non-motile cilia extend over surface Supporting cells and basal cells as reserve Olfactory mucosa “Typical” nasal mucosa Olfactory epithelium

  24. Nasal cavity Olfactory mucosa “Typical” nasal mucosa • Muscularis mucosae not present • Lamina propria blends with submucosa • Bowmans glands flush odorants Serous glands of Bowman

  25. Pharynx • Nasal • Oral • Laryngeal

  26. Extrapulmonary Components of Conducting Portion 1. Nasal cavity 2. Pharynx 3. Larynx 4. Trachea 5. Primary bronchi 6. Secondary bronchi 7. Bronchioles and terminal bronchioles

  27. Larynx Extrapulmonary-Conducting

  28. Larynx 1 1. Epiglottal cartilage 2. Thyroid cartilage 3. Cricoid cartilage 4. Tracheal cartilages 5. Vestibule 6. False vocal fold 7. Ventricle 8. True vocal fold with vocal ligament (dense reg elastic CT) 9. Vocalis muscle 6 5 7 2 2 9 8 3 3 4 4 Extrapulmonary-Conducting Trachea

  29. Larynx EXCEPTIONS: Stratified squamous moist epithelium covering epiglottis and true vocal fold Extrapulmonary-Conducting MOST of mucosa is a “typical” respiratory mucosa with NO musc. mucosae. False vocal fold VL VM

  30. Mixed glands in submucosa • Cartilage for patency • Thyroid and cricoid are hyaline • Epiglottis and smaller cartilages are elastic • Vocal apparatus • False vocal folds • Ventricle • True vocal folds • Vocal ligament - dense regular elastic CT • Vocalis muscle – skeletal muscle

  31. Extrapulmonary of Conducting Portion 1. Nasal cavity 2. Pharynx 3. Larynx 4. Trachea 5. Primary bronchi 6. Secondary bronchi 7. Bronchioles and terminal bronchioles

  32. Trachea and Primary Bronchi are identical Mucosa

  33. Respiratory epithelium with prominent basement membrane Longitudinal section Esophagus Trachea LUMEN

  34. Elastic lamina of longitudinally arranged elastic fibers • Mixed glands in submucosa • Cartilage rings for patency

  35. Intrapulmonary Components of Conducting Portion 1. Nasal cavity 2. Pharynx 3. Larynx 4. Trachea 5. Primary bronchi 6. Secondary bronchi 7. Bronchioles and terminal bronchioles

  36. Secondary bronchus 2nd Bronchus B Pulm BV Pulm BV Bronchiole 2nd Bronchus Surrounded by ALVEOLI B

  37. Mucosa Resp epithelium Lamina propria Musc. mucosae Submucosa Mixed glands Cartilage plates Adventitia Cartilage Secondary bronchus Surrounded by ALVEOLI

  38. Intrapulmonary of Conducting Portion 1. Nasal cavity 2. Pharynx 3. Larynx 4. Trachea 5. Primary bronchi 6. Secondary bronchi 7. Bronchioles and terminal bronchioles

  39. Walls of Bronchi and Bronchioles continue to decrease in size

  40. Transition from secondary bronchus to bronchiole Bronchus Bronchiole

  41. Bronchioles • No mixed glands • No cartilage • Epithelium: respiratory in largest bronchioles • Epithelium: simple columnar with cilia in terminal bronchioles

  42. Terminal bronchiole • Clara cells present among simple columnar epithelial cells • Dome-shaped • Non-ciliated with granules • Secretions lower surface tension

  43. Clara cells

  44. Elastic fibers Smooth muscle • Lamina propria: longitudinally arranged elastic fibers • Muscularis mucosae: smooth muscle at greatest thickness • Submucosa: no glands, no cartilage, no bone

  45. MAJOR SUBDIVISIONS – Conducting portion – Respiratory portion Where gas exchange actually occurs, i.e., alveoli

  46. Bronchiole to Terminal bronchiole to Respiratory bronchiole Transitions B TB RB

  47. Transitions of bronchioles Conducting Respiratory portion portion

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