RESPIRATORY SYSTEM Kristina C. Erasmo, M.D.

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

Respiratory System 1.Conducting portion 2.Respiratory portion

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)

Regions of the Nasal Cavity 1.Vestibule 2.Respiratory region 3.Olfactory region

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)

Olfactory Epithelium Cell types: – Sustentacular cells – Olfactory cells – Basal cells

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

Cartilages of Larynx Type of Cartilage 1. Paired Arytenoid Corniculate Cuneiform Upper part: elastic Lower part: hyaline Elastic 2. Unpaired Thyroid Cricoid Epiglottic Hyaline Elastic