Histology of Respiratory system
Portion of respi tract
Conducting part
Respiratory part
From nose to terminal bronchiole
To piping air to and from the lungs
From respiratory bronchiole to alveoli
Gaseous exchange btw air and blood
Structurally
Upper respiratory tract
Lower respiratory tract
Trachea
Bronchi
Bronchioles
Pulmonary alveoli
Nasal cavity
Pharynx
Larynx
Conducting portion
Respiratory portion
Principle feature
Trachea
Epithelium
Hyaline cartilage
Elastic Fibers
Smooth ms
Cleansing the inspired air
Humidify
Warming
Changes along respi tract
Nasal to end bronchus
Pseudostratified ciliated columnar epithelium
Bronchus to conducting bronchiole (terminal bronchiole)
Simple ciliated columnar epithelium
Respiratory bronchiole
Simple ciliated cuboidal epithelium
Alveolar duct
Simple CUBOIDAL epithelium
Alveoli
Simple SQUAMOUS epithelium
Up to end of bronchus
Below bronchus have no cartilage
Found thru out respi tract up to alveoli
Line the tract up to alveolar duct
3 layers
Mucosa
Submucosa
Adventitia
Epithelium
Pseudostratified ciliated columnar AND Goblet cell
Lamina propria
Thin, loose connective tissue and abundance fibroelastic fibres
Dense connective tissue
Contain seromucous gland
Mucus is thick sticky substance that act in collecting debris for swallowing
Serous fluid is thinner runny substance that keep the epithelial tissue moist and lubricated
Consist of loose connective tissue with blood vessel, nerve and fat cell
Contain cartilage connected by fibrous membrane ✅
C-shaped hyaline cartilage ring open posteriorly
Open interval is filled in by fibro-elastic tissue and trachealis ms
Bronchus
Trachea divide into right and left primary bronchi (extra-pulmonary) at sternal angle
Bronchus enter lung and subdivide into intra-pulmonary bronchi within lung
Primary bronchi has same basic structural pattern as trachea EXCEPT
Cartilage are arranged in complete circular rings
Smooth ms layer within cartilage ring in spiral fashion
Mucosa
Epithelium
PSCCE with globlet cell
Lamina propria
Separated from submucosa by discontinuous layer of smooth ms (Muscularis mucosae)
Run in spiral manner and progressively become more prominent in lower part of the airway
Submucosa
Contain sero-mucous gland
Gland decrease in number and size as the bronchi grow smaller
Solitary lymph nodules are presents
Adventitia
Extra pulmonary bronchus, hyaline cartilage ring completely encircle the lumen
Intra pulmonary bronchus, hyaline cartilage arranged in isolated plates
Bronchioles
No cartilage
No glands
Each bronchioles subdivided and branches into 5-7 terminal bronchioles
Each terminal bronchioles subdivided into 2 or more respiratory bronchioles
Respiratory bronchioles is similar to terminal bronchioles except its wall are interrupted by numerous alveoli
Mucosa
Simple ciliated columnar epithelium
Gradually replaced by simple ciliated cuboidal epithelium in respi bronchioles
Goblet cell less
Submucosa
Lamina propria is loose connective tissue with blood vessel
Many elastic fiber
Intermingle wif smooth ms forming spiral network
Smooth ms is the most prominent feature of bronchiole and effectively controls resistance to airflow within lung
No gland and no lymphoid tissue
Adventitia
Thin consist of collagen fibers
No cartilage
Terminal Bronchiole
Clara cell
Non-ciliated cell, apical projection
Protein secreting cell
Prevent luminal adhesion and airway collapse
Respiratory bronchioles
Simple ciliated cuboidal epithelium
No cartilage ,no gland ,no goblet cell
lamina propria is thin and loose and consist of spiral network of smooth ms and elastic fibers
Wall is interrupted by little out - pouching of alveoli (increase in number)
Each respi bronchioles divides into long thin walled tubes called alveolar ducts
Alveolar Duct
Discontinuous wall
Simple cuboidal cell
Spiral smooth ms are reduced to tiny local knobs
Lead to alveolar sacs
Alveolar sac
Simple squamous
Alveolar pore in the wall of alveolus communicate wif adjacent alveoli
Wall consist of elastic fibres
No ms, No cartilage no gland
Alveolus
Simple squamous
2 type of cell
Type I
Simple squamous cell
Gaseous exchange
Type II
Cuboidal cell
Produce surfactant
Interalveolar septum
Supporting tissue btw 2 alveoli
Consist of elastic fibers ,reticular cell and fibers ,dust cell (alveolar macrophage) and capillary
Blood-air barrier
3 layers
Epithelium of capillary
Epithelium of alveoli
Basement membrane