In the name of God
Respiratory System
Dr. zahiri
Respiratory system
comprising the lungs and a sequence of airways leading to the
external environment
This system providing Oxygen and eliminating Carbon dioxide
is subdivided into:
conducting portions
respiratory portions
Conducting portion
Parts:
nasal cavity, nasopharynx, larynx, trachea, primary bronchi,
secondary (lobar) bronchi, tertiary (segmental) bronchi, and
terminal bronchioles
functions :
clean, warm and moisten air prior to reaching respiratory portion
Nasal cavity
Nasal cavity composed of three regions( vestibule, respiratory and
olfactory regions)
Vestibule
Anterior portion of nasal cavity near of the nares dilated and
known as the vestibule
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lined with skin and has short, stiff hairs named vibrissae that
prevent large dust particles to enter
dermis houses numerous sebaceous glands
Posterior aspect of Nasal cavity
lined by pseudostratified ciliated columnar epithelium (respiratory
epithelium)
respiratory epithelium
Ciliated columnar cells: most common, each cell has about 300
cilia
Goblet cells: secret mucous
Brush cells: have short microvilli, nerve fibers, sensory function
Basal cells: are rounded stem cells that located near basal lamina
and show mitotic figures
Small granule cells (kulchitsky cells= DNEs)
 Subepithelial CT (lamina propria)
is richly vascularized, containing large arterial plexuses and venous
sinuses, many seromucous glands and lymphoid elements
Olfactory region
 the olfactory epithelium
 lamina propria (serous secreting Bowman’s glands, a rich vascular
plexus and many axons arising from olfactory cells of the olfactory
epithelium)
olfactory epithelium comprises three types of cells:
 Olfactory cells
olfactory
cells are bipolar neurons whose apical aspect (dendrite) is modified to
form a bulb known as olfactory vesicle
 Sustentacular cells
• has a striated border composed of microvilli, and secretory granules
• they provide physical support, nourishment
 Basal cells
• are short basophilic cells
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their apical aspects do not reach the epithelial surface
they proliferate and replace both two other cells
Paranasal sinuses
Epithelium is respiratory similar to the epithelium of nasal cavity
Lamina propria fused with periosteum of bones and houses seromucous gland
and also lymphoid elements
Sinusitis
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also known as a sinus infection or rhinosinusitis, is inflammation of
the sinuses
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Primary ciliary dyskinesia (PCD), also immotile ciliary syndrome or
Kartagener syndrome, is a rare genetic disorder that causes defects in the
action of cilia lining the respiratory tract (lower and upper, sinuses,
Eustachian tube, middle ear) and fallopian tube
Squamous metaplasia
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refers to benign non-cancerous change (metaplasia) of (non-squamous)
surfacing lining cells (epithelium) to a squamous morphology
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Metaplasia: an initial change from normal cells to a different cell type
(such as chronic irritation of cigarette smoke causing ciliated
pseudostratified epithelium to be replaced by squamous epithelium more
able to withstand the insult).
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Dysplasia: an increasing degree of disordered growth or maturation of
the tissue .
Dysplasia is still a reversible process.
However, once the transformation to neoplasia has been made, the
process is not reversible.
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Anosmia
is the inability to perceive odor or a lack of functioning olfaction—the loss
of the sense of smell.
Anosmia may be temporary, but traumatic anosmia can be permanent.
Anosmia is due to an inflammation of the nasal mucosa, blockage of nasal
passages or a destruction of one temporal lobe.
nasopharynx
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Epithelium is respiratory similar to the epithelium of nasal cavity
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Lamina propria : pharyngeal tonsil
Larynx
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connects pharynx to trachea
is lined by respiratory epithelium
Laryngeal cartilages(hyaline and elastic) are located in lamina propria
The cartilages connected to each other by ligaments and move with respect to
one another by some striated muscles
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Larynx has two folds consist of superior and inferior
Superior vestibular folds lined by respiratory epithelium
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Inferior vocal folds lined by stratified squamous nonkeratinized epithelium
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Laryngitis is an inflammation of the larynx. It causes hoarse voice or
temporary complete loss of the voice because of irritation to the vocal
folds(vocal cords).
Dysphonia is the medical term for a vocal disorder, of which laryngitis is
one cause.
croup
Epiglottis
is an elastic cartilage of larynx
 It is lined by stratified squamous epithelium on lingual surface
Pseudostratified ciliated columnar epithelium lined the laryngeal side
Serous and mucous glands located in lamina propria
Trachea
is a long tube that has 3 layers:
mucosa, submucosa and adventitia
Bifurcates into 2 primary bronchi
Trachea
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Mucosa
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Respiratory epithelium composed of 6 cell types located on a thick
basement membrane
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Goblet cells are about 30% of cells, produce mucinogen
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Ciliated columnar cells about 30% of cells, are tall which have cilia and
microvilli
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Basal cells are also about 30% of cells, they are undifferentiated stem
cells
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Brush cells are just 3% of cells, they are narrow columnar cells that their
function is unknown, but nerve ending associated with them
Serous cells are about 3% of cells, they are columnar and have serous
granule
DNES cells, constitute about 3-4% of cells, have numerous granule in
basal cytoplasm which is contain various pharmacological agents
Lamina propria
composed of loose fibroelastic CT, contain seromucous glands and lyphoid
elements, elastic lamina separate this layer from submucosa
Submucosa
Subnucosa is composed of dense irregular fibroelastic CT that houses mucous and
seromucous glands, rich in blood and lymph supply
Adventitia
Adventitia is a fibroelastic CT that houses C-shaped hyaline cartilage, at
posterior aspect of cartilage, there is a dense band of smooth muscle cells
known as trachealis muscle
Bronchial Tree
is composed of:
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2 primary bronchus that enter lungs
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3 lobar ( secondry) bronchus on right and 2 on the left
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Segmental (tertiary) bronchus
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bronchioles
Terminal bronchioles
Respiratory bronchioles
Progressively airways decreased in size and cartilage, glands,
goblet cells, and the height of epithelial cells
But increase smooth muscle cells and elastic tissue
Primary Bronchi (Extrapulmonary)
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Primary bronchi is identical to
trachea, but have smaller diameter
and thinner wall
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Cartilage is in form of irregular
plates
Smooth muscle located between
lamina propria and submucosa as 2
distinct layers
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Bronchioles
 have not any cartilage or glands
 but have few goblet cells
 In larger bronchioles epithelium
is simple columnar ciliated, with
occasional goblet cells
 In smaller bronchioles epithelium change to simple cuboidal, with
no goblet cells
 Bronchioles have a smooth muscle coats surrounded by fibroelastic
connective tissue
Bronchioles
Terminal bronchioles are terminus of conducting portion
they are lined by cuboidal cells(some with cilia) and Clara cells which have
domed apical surface
Lamina propria
is a fibroelastic CT, 1-2 layer of smooth muscle cells separate it from adventitia
Clara cells ( exocrine bronchiolar cells)
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Clara cells are columnar with dome-shaped apex
secretory granules
RER, which secret glycoproteins and surfactant-like materials
degrade toxins(SER)
divide to replace other cells
antimicrobial peptide
bronchiolitis
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Bronchiolitis is inflammation of the bronchioles, the smallest air passages
of the lungs.
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Obliterative bronchiolitis
Asthma
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(broncospasm)
Epinephrine
Respiratory Bronchioles
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are a transitional zone between
conducting and respiratory
tissues
Alveoli branching from their
walls
are lined by ciliated cuboidal
epithelium with Clara cells that
change to type I alveolar cells
Smooth muscle cells and elastic
fibers underlie epithelium
Atelectasis
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is defined as the collapse or closure of the lung resulting in reduced or
absent gas exchange.
It may affect part or all of one lung.
Alveolar Ducts
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do not have wall of their own
They are only a linear arrangements of alveoli
they end as a blind out pouching known as alveolar sac
Opening of alveolus to AD controlled by a single smooth muscle cell
embedded
Diffuse alveolar damage
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Adult respiratory distress syndrum
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Cause:
bacterial & viral infection
Toxic gases
Excessive oxygen
fat embolism syndrume
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Alveolus
•Alveolus has 200 micrometer in diameter and is the functional unit
of respiratory system
•Open as out pouching from RB, AD
•Composed of attenuated type I and type II pneumocytes
•Connective tissue between them are very scant
•Air space of two adjacent alveoli communicate through an alveolar
pore
•Interalveolar septum is between alveoli have an extensive capillary
bed
Cells of the Alveolar Septa
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Endothelial cells are nonfenestrated with a thin dark nucleus, and pinocytotic
vesicles
Type I squamous cells that cover most of alveolar surface area, they have
pinocytotic vesicles
Type II (greater alveolar) cells are cuboidal, located on alveolar surface where
septa intersect, they have foamy cytoplasm, surfactant granules (reduces surface
tension to keep alveoli open during expiration)
Alveolar macrophages that are known as dust cells
Interstitial cells consist of fibroblasts and mast cells
Elastic & reticular fibers
Type I pneumocytes (Squamus alveolar cells)
•95% of the alveolar surface is composed of the simple squamous cells
which are known as type I pneumocytes
•occluding junction attaches to other cells
•have basal lamina,
•alveolar pore formed by fusion of two adjacent type I cells
Type II pneumocytes (Septal cells)
•They are more numerous than type I
•cover just 5% of the alveolar surface
• located among type I cells, cuboidal with dome-shaped apical
•Located where adjacent alveoli separated by septum
•They have an abundance of RER, developed golgi complex,
their lamellar bodies contain pulmonary surfactant
Alveolar Macrophages (Dust cells)
•Known as type III pneumocytes
•Originate from monocytes that migrate to pulmonary interstitium
•Migrate between type I cells and enter alveolar lumen
•Maintain a sterile environment
•Assist type II to uptake surfactant
Lamellar granules
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membrane-coating granules (MCGs), lamellar
bodies,keratinosomes or Odland bodies) are secretory
organelles found in type II pneumocytes and keratinocytes.
They are oblong structures, appearing about 300-400 nm in width and 100150 nm in length intransmission electron microscopy images.
Lamellar granules fuse with the cell membrane and release their contents
into the extracellular space.
Blood Gas Barrier
•BGB is the thinnest regions of the interalveolar septum where gases can be
exchanged
This barrier is composed of:
•Type I alveolar cells
• surfactant that covers them
•Common basal lamina of the type I and endothelial cells
•Endothelial cells of capillary network
pleura
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The visceral pleura is made up of a simple squmous/cuboidal epithelium
(the mesothelium) and some connective tissues beneath it.
Small blood vessels are lymphatics are found in the connective tissue.
The presence of alveoli indicate that this is the visceral and not the parietal
pleura.
pneumothorax
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is an abnormal collection of air or gas in the pleural space that causes an
uncoupling of the lung from the chest wall.
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Like pleural effusion (liquid buildup in that space), pneumothorax may
interfere with normal breathing.
It is often called collapsed lung, although that term may also refer
to atelectasis
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Heart failure cells
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are siderophages (hemosiderin-containing macrophages)
generated in the alveoli of patients with left heart failure or
chronic pulmonary edema when the high pulmonary blood
pressure causes red cells to pass through the vascular wall.
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Chronic obstructive pulmonary disease (COPD), also known
as chronic obstructive lung disease (COLD), and chronic
obstructive airway disease (COAD), among others, is a type
of obstructive lung disease characterized by chronically poor airflow.
Long-term exposure to the irritants causes an inflammatory response in
the lungs resulting in narrowing of the small airways and breakdown of lung
tissue, known as emphysema
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