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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
Conducting Portion
• Functions:– Act as passageways for air– Warms, humidifies, cleans the air
• Components:– Nose, pharynx, larynx, trachea, bronchi,
bronchioles, terminal bronchioles
Respiratory Portion
• Functions:– Where exchange of gases takes place between the
blood and alveoli• Components:
– Respiratory bronchioles, lveolar duct, alveolar sac, alveoli
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)
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
Respiratory Region
• a.k.a Schneiderian membrane• Mucous membrane lining the nasal cavities• Lined by “respiratory epithelium” (ciliated
pseudostratified columnar epithelium with goblet cells)
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
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
Respiratory Epithelium
• Ciliated columnar cell – most abundant• Goblet cell – mucus-secreting • Serous cell – serous secretion• Brush cell – columnar cell with microvilli,
sensory cells
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
Olfactory Region
• Specialized area containing the receptor organ for smell (olfactory mucosa)
• Lined by “olfactory epithelium” (ciliated pseudostratified columnar epithelium without goblet cells)
Olfactory Region
• Basal lamina: indistinct• Lamina propria: contains branched
tubuloalveolar glands (Bowman’s glands)
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)
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
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
Olfactory Cells
• Olfactory nerve fiber – axon of the olfactory cell, travels into the lamina propria where it meets axons of other olfactory cells, unmyelinated
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
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
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
Pharynx: 3 Parts
• Nasopharynx – ciliated pseudostratified columnar epithelium with goblet cells
• Oropharynx – stratified squamous non-keratinized epithelium
• Laryngopharynx – stratified squamous non-keratinized epithelium
Larynx
• Irregular tube that connects the pharynx to the trachea
• Functions:– Conducting portion– Phonation
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
Larynx
• Lined by respiratory epithelium, except:– Vocal cords – stratified squamous non-keratinized – Aryepiglottic folds – stratified squamous non-
keratinized