The respiratory epithelium lines the respiratory tract from the nose to the trachea. It is classified as ciliated pseudostratified columnar epithelium in the upper airways, composed mainly of ciliated cells, goblet cells, and basal cells. The cilia beat in a coordinated way to move mucus up the airways via the mucociliary escalator, trapping pathogens and particles to be expelled or swallowed, protecting the lungs.

1. Respiratory Epithelium
By Group 5 Of Section 5

2. Respiratory Epithelium
 Respiratory epithelium is
a type of epithelium found
lining the respiratory tract,
where it serves to moisten
and protect the airways. It
also functions as a barrier to
potential pathogens and
foreign particles, preventing
infection and tissue injury by
action of the mucociliary
escalator.
 Respiratory epithelium
lining the mouth, nose,
throat, and trachea.

3. Respiratory Epithelium
:Classification
 Respiratory epithelium
lining the upper (cranial)
airways is classified as
ciliated pseudostratified
columnar epithelium. This
designation is due to the
arrangement of the multiple
cell types composing the
respiratory epithelium. While
all cells make contact with
the basement membrane and
are, therefore, a single layer
of cells, the nuclei are not
aligned in the same plane.
Hence, it appears as though
several layers of cells are
present and the epithelium is
called pseudostratified.

4. Respiratory Epithelium
:Classification
 The majority of cells composing
the ciliated pseudostratified
columnar epithelium are of three
types:
a) ciliated cells.
b) goblet cells.
c) basal cells.
 The ciliated cells are columnar
epithelial cells with specialized
ciliary modifications.
 Goblet cells, so named
because they are shaped like a
wine goblet, are columnar
epithelial cells that contain
membrane-bound mucous
granules and secrete mucus,
which helps maintain epithelial
moisture and traps particulate
material and pathogens moving
through the airway.

5. Respiratory Epithelium
Classification
 The basal cells are small, nearly cuboidal cells thought to have
some ability to differentiate into other cells types found within
the epithelium. For example, these basal cells respond to injury
of the airway epithelium, migrating to cover a site denuded of
differentiated epithelial cells, and subsequently differentiating to
restore a healthy epithelial cell layer.
 Certain parts of the respiratory tract, such as the oropharynx,
are also subject to the abrasive swallowing of food. To prevent
the destruction of the respiratory epithelium in these areas, it
changes to stratified squamous epithelium, which is better suited
to the constant sloughing and abrasion. The squamous layer of
the oropharynx is continuous with the esophagus.

6. Respiratory Epithelium
Mucociliary Escalator
 The cilia of the respiratory
epithelium beat in concert
cranially, effectively moving
secreted mucus containing
trapped foreign particles
toward the laryngopharynx,
for either expectoration or
swallowing to the stomach
where the acidic pH helps to
neutralize foreign material
and micro-organisms. This
system is collectively known
as the mucociliary escalator
and serves two functions: to
keep the lower respiratory
tract sterile, and to prevent
mucus accumulation in the
lungs.

7. Respiratory Epithelium
Mucociliary Escalator
 The mucocilliary escalator
is vital for the movement
of mucus up the
respiratory tract to the
pharynx. The mucus layer
is biphasic with a serous,
sol layer in which the cilia
beat and, above this, a
viscoelastic or gel layer.
Due to the viscous
properties of this upper
mucous layer, the tips of
the cilia catch in the layer,
which may contain
particulate matter, and
drag it cranially toward the
laryngopharynx.