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Histology of Respiratory system, Conducting portion, Respiratory portion -…
Histology of Respiratory system
Portion of respi tract
Conducting part
From nose to terminal bronchiole
To piping air to and from the lungs
Respiratory part
From respiratory bronchiole to alveoli
Gaseous exchange btw air and blood
Structurally
Upper respiratory tract
Nasal cavity
Pharynx
Larynx
Lower respiratory tract
Trachea
Bronchi
Bronchioles
Pulmonary alveoli
Principle feature
Epithelium
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
Hyaline cartilage
Up to end of bronchus
Below bronchus have no cartilage
Elastic Fibers
Found thru out respi tract up to
alveoli
Smooth ms
Line the tract up to
alveolar duct
Trachea
3 layers
Mucosa
Epithelium
Pseudostratified ciliated columnar
AND
Goblet cell
Lamina propria
Thin,
loose connective tissue
and abundance fibroelastic fibres
Submucosa
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
Adventitia
Consist of
loose connective tissue
with
blood vessel, nerve and fat cell
Contain
cartilage
connected by
fibrous membrane
:check:
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
Lamina propria is
loose connective tissue
with blood vessel
Submucosa
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
Conducting portion
Respiratory portion