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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