1st Lecture of Respiratory Histology by Dr Roomi

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HISTOLOGY OF RESPIRATORY

SYSTEM

BY

DR. MUDASSAR ALI ROOMIDR. MUDASSAR ALI ROOMI(MBBS, M. PHIL.)

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RESPIRATORY SYSTEM

Definition: The complex of organs and tissues which are

necessary to exchange blood carbon dioxide (CO2) with air

oxygen (O2) is called the respiratory system.

It consists of:1. structures, which function as ducts, and which together are

called the conductive portion of the respiratory system

2. structures which form the respiratory portion of the

respiratory system, in which the exchange of CO2

and O2

is

occurring and

3. the parts of the thoracic musculo-skeletal apparatus and

specializations of the lung which allow the movement of air

through the respiratory system - the ventilating mechanism.

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Conducting portion ofrespiratory system: it

includes the nasal cavities, pharynx,larynx

trachea, bronchi till terminal bronchioles.

Its main function is air conditioning.

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Respiratory division ofrespiratory system: it

comprises of respiratory bronchioles, alveolar

ducts, alveolar sacs, pulmonary atria and

alveoli.

Its main function is the exchange of gases.

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Main Functions ofrespiratory system

Gaseous exchange

Olfaction

phonation

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NasalCavity

The Nasal cavity is divided into three structurally andfunctionally different parts.

1. THE VESTIBULES OF NOSE:

the first1

.5 cm of the conductive portion followingthe nostrils is called as vestibule.

lined by skin wihich has a keratinised stratifiedsquamous epithelium.

Skin also has sebaceous glands and sweat glands

here. Hairs (vibrissae), which filter large, coarse particulate

matter out of the airstream are also present.

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NasalCavity

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2. RESPIRATORY REGION OF NASAL CAVITY:

At the transition from the vestibule to the respiratoryregion of the nasal cavity the epithelium becomes firststratified squamous and then pseudostratified columnar

and ciliated. This type of epithelium is characteristic for all conductive

passages dedicated to the respiratory system and thereforealso called respiratory epithelium. Mucus producing gobletcells are present in this epithelium.

The surface of the lateral parts of the nasal cavity is throwninto folds by bony projections called conchae. These foldsincrease the surface area and facilitate the air conditioning.

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RESPIRATORY EPITHELIUM

Cell types in the

respiratory epithelium

are:

1. Ciliated columnar cells

2. Goblet cells

3. Basal cells

4. Brush cells5. Small granule cells

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Cilia

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IMMOTILE CILIA SYNDROME

a disorder that causes infertility in men and

chronic respiratory tract infections in both

sexes, is caused by immobility of cilia and

flagella induced, in some cases, by deficiency

ofdynein, a protein normally present in the

cilia. Dynein participates in the ciliary

movement.

Kartaganer syndrome

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IMMOTILE CILIA SYNDROME

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3. OLFACTORY REGION IN THE NASAL CAVITY: Mucosa on roof of nasal cavity, the superior concha and the

superior nasal septum forms the olfactory region of the nasal cavity.

stereocilia in the epithelium of the olfactory region arise from

olfactoryreceptor cells (bipolar cells). The cell membrane covering the surface of the cilia contains

olfactory receptors which respond to odour-producing substances.

The olfactory cells and their processes receive mechanical andmetabolic support from supporting cells (sustentacular cells).

The supporting cells contain lipofuscin granules, which give a

yellow-brown colour to the surface of the olfactory region. Basal cells can divide and differentiate into either olfactory or

supporting cells (MCQ).

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COMPARISON

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PARANASAL AIR SINUSES

Frontal, maxillary, ethmoid and sphenoidal air

sinuses.

It contains the respiratory epithelium. Functions: air conditioning, resonance and

making the skull light in weight.

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Sinusitis

It is an inflammatoryprocess of the sinuses

that may persist for

long periods of time.

It is mainly because of

obstruction of drainage

orifices of the sinuses.

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PHARYNX

The pharynx connects the nasal cavity with the larynx.

Depending on the extent of abrasive forces on theepithelium, the pharynx is either lined with respiratoryepithelium (nasopharynx) or with a stratifiedsquamous epithelium (oropharynx and hypopharynx),which also covers the surfaces of the oral cavity andthe oesophagus.

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 airflow

and allow the production of sound. The vocal folds are lined by stratified

squamous epithelium and contain the muscle

(striated, skeletal) and ligaments needed to

control the tension of the vocal folds.

The larynx is supported by a set of cartilages.

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LARYNX

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LARYNX

Pseudostratified ciliated columnar epitheliumlines false vocal fold, as in posterior epiglottis

Ventricle, a deep indentation, separates false

vocal fold from true vocal foldTrue vocal fold lined by stratified squamous

nonkeratinized epithelium

Hyaline thyroid cartilage and cricoid cartilage

provide support for the larynx. Epithelium in lowerlarynx changes back to

pseudostratified ciliated columnar

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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 a laryngealsurface.

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 pseudostratified ciliatedcolumnar epithelium.

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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