2nd Lec of Respiratory Histology by Dr Roomi

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BY

DR. MUDASSAR ALI ROOMIDR. MUDASSAR ALI ROOMI

(MBBS, M. PHIL.)

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The olfactory epithelium has:

(a) Columnar epithelium with goblet cella

(b) columnar stratified epithelium

(c) bipolar neurons(d) Clara cells

(e) Dust cells

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The respiratory epithelium of the conducting

portion of the respiratory tract has:

(a) stratified squamous epithelium

(b) pseudostratified columnar

epithelium(c) No ciliated cells

(d) No goblet cells

(e) Cells with stereocilia

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PHARYNX

The pharynx connects the nasal cavity with thelarynx.

Depending on the extent of abrasive forces on theepithelium, the pharynx is either lined withrespiratory epithelium ( in nasopharynx) or with astratified squamous epithelium (in oropharynx andhypopharynx)

Lymphocytes frequently accumulate beneath theepithelium of the pharynx (pharyngeal tonsils).

The nasal cavity and pharynx form the upperrespiratory passages.

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LARYNX

The larynx connects the pharynx and trachea.

The vocal folds of the larynx control airflowand allow the production of sound.

The true vocal folds are lined by stratifiedsquamous non-keratinized epithelium(MCQ)and contain the muscle (striated, skeletal) andligaments.

Respiratory epithelium lines the false vocalfold, as in posterior epiglottis.

The larynx is supported by a set of cartilages.

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LARYNX

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EPIGLOTTIS

The epiglottis is the superior portion of the larynx that projects

upward from the larynxs anterior wall. It has both a lingual and alaryngeal surface.

A central elastic cartilage of epiglottis forms the framework of

the epiglottis.

Its lingual mucosa ( anterior side) is lined with a stratified

squamous nonkeratinized epithelium . The lingual mucosa with its stratified squamous epithelium covers

the apex of the epiglottis and about half of the laryngeal mucosa

(posterior side).

Toward the base of the epiglottis on the laryngeal surface , the

lining stratified squamous epithelium changes to pseudostratifiedciliated columnar epithelium.

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Located below the epithelium in the lamina

propria on the laryngeal side of the epiglottis

are tubuloacinar seromucous glands.

In addition to the tongue, taste buds and solitarylymphatic nodules may be observed in the

lingual epithelium or laryngeal epithelium

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Trachea

1. Mucosa:

it is lined with Pseudostratified columnar,ciliated epithelium with goblet cells (respiratory

epithelium).2. Submucosa: it contains Sero-mucous glands

3. 16-20 C-shaped rings of hyaline Cartilage +trachialis muscle

4. adventitia: it has loose connective tissue

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Bronchi

Extrapulmonary bronchus is just like thetrachea.

Intrapulmonary bronchi have got thefollowing differences from the

extrapulmonary bronchi:1. Pseudostratified columnar, ciliated epithelium

(shorter) Goblet cells (fewer)

2. Irregular Cartilage plates all around the wall

3. Smooth muscle layer is complete

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Cancer of lung (bronchogenic

carcinoma)

Smoking is a major reason

Pseudostratified epithelium changes to

stratified squamous epithelium

(squamous metaplasia)

Dysplasia leads to cancer

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Bronchioles

1 mm or less in diameter.

Simple columnar or cuboidal ciliated

epithelium goblet cells present in larger bronchioles

but absent in the smaller ones.

No cartilage in their walls

Mucosa contains no glands.

Smooth muscle (relatively abundant)

Clara cells (non ciliated cells): producesurfactant and function as stem cells.

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Respiratory Bronchiole

Simple cuboidal, ciliated epithelium

Goblet cells and glands are entirelyabsent.

Clara cells are present here.

Alveolar outpocketing on its walls.

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Cystic fibrosis

Cystic fibrosis: it is due to abnormal Cl-

transport by Clara cells

Associated with thick mucus and

recurrent lung infections.

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asthma

Recurrent spasm of bronchiolar smooth

muscles.

It is a type of hypersensitivity reaction.

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Alveoli

Type I alveolar cells or type 1 Pneumocytes (squamous

alveolar cells):

flattened for gas exchange

40% of all cells in the wall of alveoli but cover 90-95% ofthe surface area.

With capillary endothelium, form the thin blood-air

barrier (0.6 um thick).

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Type II alveolar cells or type 2 Pneumocytes (great

alveolar cells):

cuboidal in shape

60% of all cells in the wall of alveoli but cover 5-10% ofthe surface area.

Luminal surface of these cells bear microvilli

Are secretory cells and produces surfactant

Contain numerous secretory granules

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Alveolar Macrophages (dust cells)

Are monocytes that enter pulmonary

connective tissue and alveoli

are somponent of reticuloendothelial

system

Clean alveoli of invading organisms and

phagocytose particular matter

Their cytoplasm is laiden withphagocytosed carbon and dust pariticles.

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emphysema

Destruction of

alveolar walls.

Large air spaces.

wasted ventilation.

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The type I alveolar cells:

(a) are columnar epithelial cells

(b) are rounded or cuboid in shape

(c) have abundant microvilli on theirsurface

(d) secrete surfactant

(e) are involved in gaseous exchange

with the blood

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Respiratory surfactant:

(a) is secreted by type II (great alveolar)

cells

(b) increases surface tension of alveoli

(c) Has nothing to do with surface tension

of alveoli

(d) Not essential for correct respiratory

function

(e) mainly a triglyceride

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The alveolar dust cells:

(a) are phagocytic

(b) secrete surfactant

(c) produce antibodies(d) Are mast cells

(e) develop from eosinophils