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. Vestibule2. Respiratory region3. 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 LarynxType of Cartilage

1. Paired Arytenoid

Corniculate Cuneiform

Upper part: elasticLower part: hyaline

Elastic

Elastic

2. Unpaired Thyroid Cricoid Epiglottic

Hyaline

Hyaline

Elastic