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RESPIRATORY SYSTEM

The human respiratory system is crucial for gas exchange, involving the intake of oxygen and removal of carbon dioxide. It comprises the lungs and an intricate network of passages, including the nose, pharynx, larynx, trachea, and bronchi. The system functions in two portions: the conducting portion, which warms, humidifies, and cleans air, and the respiratory portion, where gas exchange occurs in alveoli. Key elements like olfactory epithelium in the nasal cavity and specialized cells play vital roles in smell and airway maintenance.

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RESPIRATORY SYSTEM

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  1. RESPIRATORY SYSTEM Kristina C. Erasmo, M.D.

  2. Respiratory System • Main function: gas exchange (intake of oxygen by the blood, eliminate carbon dioxide) • Consists of the lungs and the series of passages leading to them

  3. Respiratory System • Conducting portion • Respiratory portion

  4. Conducting Portion • Functions: • Act as passageways for air • Warms, humidifies, cleans the air • Components: • Nose, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles

  5. Respiratory Portion • Functions: • Where exchange of gases takes place between the blood and alveoli • Components: • Respiratory bronchioles, lveolar duct, alveolar sac, alveoli

  6. Nose • Hollow organ • Divided into 2 irregularly-shaped spaces (nasal cavities, nasal fossae) by the nasal septum • Nasal turbinates – 3 shelf-like structures on the latreral wall of each nasal cavity (superior, middle, inferior)

  7. Regions of the Nasal Cavity • Vestibule • Respiratory region • Olfactory region

  8. Vestibule • Most dilated, anterior part of the nasal cavity • Lined by stratified squamous non-keratinized epithelium • Lamina propria composed of dense CT • Contains some sebaceous, sweat glands, hair follicles with thick, stiff hair

  9. Respiratory Region • a.k.a Schneiderian membrane • Mucous membrane lining the nasal cavities • Lined by “respiratory epithelium” (ciliated pseudostratified columnar epithelium with goblet cells)

  10. Respiratory Region • Lamina propria: with serous and mucous tubuloalveolar glands • Basal lamina separates the nasal epithelium from the underlying lamina propria • Cavernous sinuses – venous plexuses beneath the epithelium

  11. Respiratory Epithelium • Lines not only the nasal cavity, also most of the conducting portion • Comprises different cell types: • Ciliated columnar cell • Goblet cell • Serous cell • Brush cell • Basal cell • Granule cell

  12. Respiratory Epithelium • Ciliated columnar cell – most abundant • Goblet cell – mucus-secreting • Serous cell – serous secretion • Brush cell – columnar cell with microvilli, sensory cells

  13. Respiratory Epithelium • Basal cell – short, round cell resting on basal lamina, functions as a stem cell • Granule cell – looks like basal cell but contains numerous dense granules

  14. Olfactory Region • Specialized area containing the receptor organ for smell (olfactory mucosa) • Lined by “olfactory epithelium” (ciliated pseudostratified columnar epithelium without goblet cells)

  15. Olfactory Region • Basal lamina: indistinct • Lamina propria: contains branched tubuloalveolar glands (Bowman’s glands)

  16. Olfactory Epithelium • Cell types: • Sustentacular cells • Olfactory cells • Basal cells

  17. Sustentacular Cells • a.k.a. supporting cells • Tall, slender cells with broad apices and narrow bases • Apical surface: numerous microvilli bathed in mucus • Nuclei: ovoid, off-center • Cytoplasm: contains small Golgi, numerous sER, pigment granules (lipofuscin)

  18. Olfactory Cells • Lodged between sustentacular cells • Spindle-shaped bipolar neurons • Nuclei: round, lie below nuclei of sustentacular cells but above the nuclei of basal cells

  19. Olfactory Cells • Dendrite: between 2 adjacent sustentacular cells, terminates in a small bulb-like expansion on the surface of the epithelium (olfactory vesicle) • Olfactory cilia – 6-10 fine hairlike processes radiating from olfactory vesicle, non-motile, the actual receptor elements of the olfactory cell

  20. Olfactory Cells • Olfactory nerve fiber – axon of the olfactory cell, travels into the lamina propria where it meets axons of other olfactory cells, unmyelinated

  21. Basal Cells • Small, round or conical, deep-staining • Single layer • Occupy area between the bases of sustentacular and olfactory cells • Nuclei: dark, ovoid • Branching cytoplasmic processes • Stem cells that differentiate into sustentacular or olfactory cell

  22. Paranasal Sinuses • Air-filled spaces within the bones of the skull and face communicating with the nasal cavity • Frontal, maxillary, ethmoidal, sphenoidal • Walls: lined by mucous membrane • Epithelium: respiratory epithelium

  23. Pharynx • Funnel-shaped fibromuscular tube • Extends from the base of skull to the hyoid bone, where it is continuous with the esophagus • Tube that is common to both the respiratory and digestive system

  24. Pharynx: 3 Parts • Nasopharynx – ciliated pseudostratified columnar epithelium with goblet cells • Oropharynx – stratified squamous non-keratinized epithelium • Laryngopharynx – stratified squamous non-keratinized epithelium

  25. Larynx • Irregular tube that connects the pharynx to the trachea • Functions: • Conducting portion • Phonation

  26. Larynx • Framework is formed by 3 unpaired cartilages and 3 paired cartilages • Extrinsic muscles – support larynx, connect larynx to surrounding structure, raise the larynx during deglutition • Intrinsic muscles – regulate the tension of the vocal cords resulting to phonation

  27. Larynx • Lined by respiratory epithelium, except: • Vocal cords – stratified squamous non-keratinized • Aryepiglottic folds – stratified squamous non-keratinized

  28. Cartilages of Larynx

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