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Histology of Respiratory
SystemDr. Mirna Muis, Sp.Rad
Dept. of HistologyFaculty of Medicine, Hasanuddin Univ.
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Respiratory System
Respiratory system consist of the pairedlungs & the series of air passages thatlead to & from the lungs.
the RS devided into 2 principal region:
1. Conduction portion
2. Respiratory portion
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Conducting portion consist of : nasal cav,nasopharynx & oropharynx, larynx, trachea, pair
of main bronchi, broncioles.
Respiratory portion consist of: respiratorybronchioles, alveolar duct, alveolar sac, alveoli.
Air passing through the respiratory passagesmust be conditionedbefore reaching the
terminal respiratory units. Its include: warming,
moistening & removal of particulate materials.
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Diagram of respiratory passages
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Nasal Cavities
Paired chambers separated by a bony &cartilaginous septum.
Each chamber communicates ant with extenvironment through nares & post withnasopharynx through choanae.
Divided into 3 regions :- vestibule
- respiratory segm.
- Olfactory segm.
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Vestibule of the Nasal Cavity
Lined with stratified squamous epith.
Contains : stiff hairs, vibrissae entraplarge particulate.
Posteriorly stratified sguamous epithbecome thinner & transition to thepseudostratified epith that characterizesthe respiratory segment sebaceousglands are absent.
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Respiratory segment of NC
Constitutes most of the volume of NC
Lined with ciliated pseudostratified columnarepith.
Nasal septum medial wall of resp segm issmooth but lateral wall (conchae) is bonyprojection.
Conchae plays a dual role : increase surfacearea & cause turbulence in airflow to allow moreefficient conditioning of inspired air.
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Respiratory segment of NC
The Epithelium of RS is composed of 5 celltypes : Ciliated cells: covering the surface of epith Goblet cells: synthesize & secrete mucus.The mucus &
other secr are move toward the pharynx by means ofcoordinated sweeping movements of cilia normallyswallowed
Brush cells: has blunt microvilli. Small granule cells: contain secretory granules
Basal cells: steam cell from which other cell types arise.Epithelium of RS of NC is essentially same as theepithelium lining most of the parts that follow in theconducting system.
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Olfactory Segment of NC
The epithelium is thicker than the nonsensory epith & it servesas the receptor for smell. Its consists of :- Olfactory cells: bipolar neurons that span the thickness
of the epithelium.
- Supporting or sustentacular cells: columnar cells withapical microvilli.
- Basal cells: steam cells from which the olfactory &supporting cell differentiate.
- Brush cells
Lamina propria directly contiguous with periosteum. Containsnumerous blood & lymphatic vessels, nerves & olfactory(bowmans gland).
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OLFACTORY MUCOSA
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OLFACTORY MUCOSA
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Paranasal Sinuses
PS are air filled spaces in the bones of thewalls of the nasal cavity.
Lined by respiratory epithelium with
numerous goblet cells. Named for the bone which they are found,
i.e, ethmoid, frontal, sphenoid & maxillar.
Mucus produced in the sinuses is sweptinto nasal cav by coordinated cilliarymovement.
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Larynx
Irregular tube that connects pharyng to trachea.
Within lam propria lie a number of laringeal cartilages.
Larger cartilages are hyaline, smaller cartilage are
elastic.
Function of the cartilages :
- Maintainance an open airways
- prevent swallowed food/fluid from entering trachea- participate in producing sounds for phonation.
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LARYNX
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Epiglottis
Mikr : devided into :
- Pars Lingualis : stratified squamous ephit.
- Pars Laringealis : respiratory ephitelium Lamina propria : seromucous gland
Elastic cartilage located in the middle.
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Vocal cords
Located in the post of epiglottis. Devided into :
- cranial fold false focal cord: resp epith,
gland ++, have no intrinsic musc so do notmodulate in phonation.- caudal fold true focal cord : stratified
squamous epith serves to protect the mucosa
from abrasion caused by the rapidly moving airstream, has no gland, have intrinsic & extrinsicmusc.
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Trachea
A short, flexible, air tube (2,5 cm in diameter & 10 cmlong)
Its wall assists in conditioning inspired air.
Divided into 2 main bronchi.
The wall consist of 4 definable layers :
- mucosa: composed of ciliated, pseudostratified
epith & an elastic fiber rich lamina propria.
- submucosa: composed of slightly denser conn tissue
than the lamina propria.
- cartilaginous layer: composed of C-shaped hyaline
cartilages.
- Adventitia
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Trachea
Tracheal epithelium is similar to resp epith.
Ciliated columnar cells, goblet cells & basal cellsprincipales cells types in tracheal epith.
Brush cells, small granule cells in small number. C-shaped hyaline cartilage to prevent collapse of
tracheal lumen, particularly during expiration.
Fibroelastic tissue & smooth muscle (trachealis
muscle) also present.
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TRACHEA
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TRACHEA
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Bronchi
The wall of bronchus have 5 layers :- Mucosa: pseudostratified epithelium,height of cells decrease as the bronchus
decrease in diameter.- Muscularis:continous layer of smooth musclesin the larger bronchi.
- Submucosa:contain gland & adiposed tissue.
- cartilage layer:become smaller as bronchialdiameter diminishes.
- Adventitia
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Bronchioles
Air conducting ducts that measure 1 mm or less.
Cartilage plates & glands are not present inbronchioles.
Epithelium: pseudostratified ciliated columnar
epithelium transform into simple cilliated columnarand become cuboidal epithelium as the ductnarrow.
Goblet cells still present in the largest bronchiolesbut disappear in terminal bronchioles.
Respiratory bronchioles contains both ciliated cells& clara cells but distally clara cells predominant.
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Alveoli
Alveoli are the actual sites of gas exchangebetween the air & the blood. Each adult lung has about 150-250 million alveoli,
their combined internal surface area is 75 m2.
Each alveolus is a thin wall polyhendral chambers0,2 mm in diameter.Alveolar duct : elongated airways, almost have no
walls only alveoli as their peripheral boundary.Rings of smooth muscles are present in the
interalveolar septa.Alveolar sac: spaces surrounded by clusters of
alveoli. Usually occur at termination of an alveolarduct.
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Alveoli
Alveolar epithelium is composed of type I & type IIalveolar cells & occasional brush cells.
Type I alveolar cells are extremely thin squamouscells that line most (95%) of the surface of the
alveoli. Joint to another cell by occluding juntions. Type II alveolar cells/ septal cell are secretory
cells. Cover only 5 % of alveolar air surface. Richin the mixture of phospholipids, neutral lipids &proteins that secreted by exocytosis to form
surface-active agent surfactant Brush cells: only few in number serve as receptors
that monitoring air quality in the lung.
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Thank you for your kind attention