Respiratory system Histology

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Respiratory system :

Respiratory system Dr Pankaj Maheria

Bronchial asthma:

Bronchial asthma A 32 year old strong and stout male patient came for his complaints of bronchial asthma. He was suffering from bronchial asthma since the last 5 years. He would start with a cough, thick whitish expectoration, and then dyspnoea. He would get severe difficulty in breathing. He would require inhalers and bronchodilators. The asthma would get triggered by ice creams, cold drinks, dust, oily and fried food. He had several attacks in the winter and rainy season and they would be more severe in the night at 3-4 am. Each attack would last for 10-12 days.


Questions???? What causes asthma? How are the airways involved in the pathogenesis of the disease and symptoms? Which structures of the respiratory tree show changes and what are those changes? What is the treatment of asthma?

Learning Objectives: :

Learning Objectives: Describe the organization of the respiratory tract into conducting and respiratory portions. Identify the structure and function of the respiratory mucosa. Correlate structure to function of trachea, primary and secondary bronchi, bronchioles of different types, alveolar ducts and alveoli. Know function of the blood-air barrier and alveolar macrophages.


respiration Two different process but interrelated processes. Cellular respiration Mechanical respiration

Functional division :

Functional division Conducting portion Upper respiratory tract (Nasal cavity , pharynx, larynx ) Lower respiratory tract (trachea, bronchi, bronhioles ) Respiratory portion Alveolar duct, alveolar scas and alveoli Function: Passage of air Condition of air Function: Exchange of O 2 and CO 2

Conducting portion:

Conducting portion

General structure:

General structure Four coat Mucosa Epithelium: pseudostratified ciliated columnar with goblet cells Lamina propria Submucosa : Loose connective tissue with mixed glands Cartilage layers Hyaline cartilage with smooth muscle Adventitia Fibro-elastic connective tissue merging with surrounding tissue

Structure change in conducting portion :

Structure change in conducting portion Epithelium : Thickness decrease Pseudostratified to simple cuboidal Goblet cell: Decrease in number and complete disappear in bronchiole. Sub-mucosal gland: Decrease and complete disappear in bronchiole.

Structure change in conducting portion :

Structure change in conducting portion Elastic fibers: Increase in amount Cartilage: Gradually reduce and disappear distally Smooth muscle : Relatively increase

Nasal cavity:

Nasal cavity Beginning of respiratory system Nostril in front to posterior nasal apertures behind Bone and cartilage covered by mucous membrane. Nasal septum

Structure :

Structure According to lining of epithelium. Vestibule Skin Olfactory region Olfactory epithelium and connective tissue Respiratory region Respiratory epithelium

Olfactory region:

Olfactory region Smaller area Thick yellow olfactory mucosa Function as organ of smell

Olfactory region:

Olfactory region Olfactory mucosa Thick olfactory epithelium and underlying connective tissue and lamina propria Lamina propria contain serous gland (Bowman’s gland) bundle of olfactory nerve (fila olfactoria), blood vessels and lymphatic's.

Olfactory region:

Olfactory region Olfactory epithelium: Olfactory cells : modified bipolar nerve cells Sustentacular cells : tall columnar cells , supporting cells Basal cells

Vomero-nasal organ of Jacobson :

Vomero-nasal organ of Jacobson Vomero-nasal cartilage contains on each side a mucous pouch Extends blindly upward from the lateral incisive canal for a distance of about 2 lo 6 mm. The pouches are lined by the olfactory epithelium and are supplied by the olfactory nerves. Are rudimentary in mankind, but well developed in macrosmatic animals like rabbits, cat and dogs.

Respiratory region :

Respiratory region Respiratory mucosa , pink in color. Contain respiratory epithelium Cells of respiratory epithelium Ciliated cells Goblet cells Brush cells Granule cells Basal cells


Pharynx Tube extending from base of skull to level of 6 th cervical vertebra Three part Nasopharynx, Oropharynx Laryngopharynx Structure Mucosa Submucosa Muscle Adventitia

Larynx :

Larynx Production of voice Cartilaginous framework which is made of nine cartilages Hyaline cartilage: Thyroid Cricoid Arytenoid Elastic cartilage Epiglottis Cuneiform Corniculate

Trachea :

Trachea Flexible cartilaginous tube allowing expansion in width and extension in length during inspiration 10 cm long and 2 cm wide Number of incomplete ‘C’ shaped cartilaginous ring Strong fibroelastic membrane Involuntary trachealis muscle where cartilage absent Lined by respiratory epithelium


Structure Mucosa Ciliate pseudostratified columnar Tall Cilia around 270 per cells Basement membrane Numerous goblet cells Submucosa: Loose connective tissue Contain : mixed glands,


Structure Cartilage and smooth muscle layer 16 to 20 in number ‘C’ shaped Deficient behind Hyaline cartilage First broadest , last is carina Free ends is bridged by smooth muscle( Trachealis) and fibro-elastic ligaments Adventitia Fibro-elastic CT contain neurovascular structure.

Principal bronchus:

Principal bronchus Divide at level of T4 Enter in lung at hilum Similar to trachea but differs in several detail Respiratory epithelium ; less tall Lamina propria : more elastin in upper layer, separate from submucosa by a layer of smooth muscle. Submucos: fewer seromucinous gland

Lung ( intrapumonary bronchus and its subdivision , lung parenchyma):

Lung ( intrapumonary bronchus and its subdivision , lung parenchyma) Principal organ of respiration Situated in thoracic cavity on each with pleura Contains : terminal part of bronchial tree Intrapulmonary bronchus Bronchiole Respiratory bronchiole Lung parenchyma ( Alveolar duct and alveoli with blood vessels )

Structure :

Structure Lining epithelium of bronchial tree gradually decrease in thickness Gland and goblet cells Decrease and disappear at distal end. Cartilage part : Decrease Elastic part : Increase

Intrapulmonary bronchus (Secondary and tertiary bronchi):

Intrapulmonary bronchus (Secondary and tertiary bronchi)

Intrapulmonary bronchus:

Intrapulmonary bronchus Mucosa Epithelium Pseudostratified ciliated columnar Lamina propria Rich elastic fibers Mucosa is thrown into fold. Smooth muscle Spirally running cris - cross bundles of smooth muscle. Muscle discontinues

Intrapulmonary bronchus:

Intrapulmonary bronchus Submucosa Few seromucous gland Cartilage layer and adventitia Intrapulmonary bronchus – isolated plate of hyaline cartilage

Bronchiole :

Bronchiole Formed Repeated division of tertiary bronchus. Pulmonary lobules – divide 5 to 7 terminal bronchiole Diameter is less than 1 mm.

Bronchiole :

Bronchiole Simple columnar or cuboidal ciliated epithelium without goblet cells. Goblet cell replace by Clara cells which secret glycoprotein that protect the bronchiolar lining against oxidative pollutants and inflammation.

Bronchiole :

Bronchiole Thick smooth muscle layer Many elastic fibers No gland No cartilage

Respiratory bronchus :

Respiratory bronchus Derived from terminal bronchioles Transitional part Structure similar to terminal bronchioles except that its wall is interrupted by alveoli as outpouchings.

Respiratory bronchus :

Respiratory bronchus Wall between the outpouchings: Ciliated cuboidal epithelium with Clara cells Supported by smooth muscle and elastic fibers. Alveoli : squamous alveolar epithelial cells. Distally divide into alveolar duct.

Alveolar duct:

Alveolar duct Aries: respiratory bronchiole Lining epithelium: squamous cells supported by smooth muscle fibers and fibroelastic connective tissue. Many alveoli open it Open in atria which communicate with alveolar sac and alveoli.

Clara cells:

Clara cells Secretory granules and a bulging apical cytoplasm. Function: Production of one of component of surfactant Act as stem cells Contain enzyme system which can detoxify noxious substance


alveoli Parenchyma of lung Sac like evagination at terminal part of bronchial tree Responsible for exchange of gases between air and blood Honeycomb appearance. Its has three parts Surface epithelium Supporting tissue Blood vessels

Surface epithelium :

Surface epithelium Two type of cells Know as pneumocytes Type Pneumocytes I Pneumocytes II

Type I Pneumocytes ( squamous epithelial cells):

Type I Pneumocytes ( squamous epithelial cells) Extremely thin cells (25 nm thick) Covers 97% of alveolar surface Contain abundant pinocytic vesicle which play a role in absorption surfactant and removal of particulate contaminants from surface. Part of blood air barriers.

Blood air barriers :

Blood air barriers Three layers Attenuated cytoplasm of type I pneumocytes Basement membrane Thin cytoplasm of capillary endothelium.

Type II pneumocytes (great alveolar cells / septal cells / surfactant cells):

Type II pneumocytes (great alveolar cells / septal cells / surfactant cells) Roughly cuboidal in shape. Found in group of 2 to 3 cells between type I cell. Cover 3% of alveolar surface. Microvilli Foamy vacuolated cytoplasm due to presence of lamellated bodies. Pulmonary surfactant Nuclei: large and plump with dispersed chromatin and prominent nucleus

Supporting tissue : Interalveolar septum:

Supporting tissue : Interalveolar septum Between two squamous epithelium Network of capillary supported by reticular and elastic fibers and occasionally fibroblast, mast cells and macrophages. Pores (alveolar pore of Kohn) Help in passage of air from one to another alveoli thus equalizing pressure in alveoli .

Supporting tissue:

Supporting tissue Elastic fibers Expand during inspiration Passive contraction during expiration Reticular fibers: Prevent over distension.

Blood vessels :

Blood vessels Capillary : 7 to 10 µm Line: continues endothelium Pinocytes visible in endothelium

Alveolar macrophage :

Alveolar macrophage Derived from monocytes Part of mononuclear phagocytic system Contain: Phagocytosed inhaled carbon and dust particle. Pass on to pneumocytes I through pinocytic vesicle. Sometime migrate from septum to alveolar surface and carried to pharynx through sputum.

PowerPoint Presentation:

Emphysema Interstitial fibrosis Bronchial asthma

PowerPoint Presentation:

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