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
Functions
Clean the air inhaled by
the body before it reaches
the lungs. The respiratory
lining is covered in mucus,
which serves to capture
pollutants as they travel
through the respiratory
cavities. Once captured,
pollutants are swept back
toward the outside of the
body by small, hair-like
structures called cilia.
These cilia are constantly
beating in a wave-like
motion that moves foreign
objects up and out of the
body.
7. Respiratory Epithelium
Functions
Warming air from the
outside world before it
reaches the lungs is
another important function
of the lining. The
respiratory epithelium that
lines nasal passages is
particularly blood-rich. As
air passes through the
nose, warmth from the
blood passing through the
blood vessels underneath
the lining is transferred to
the air. The warmed air
then continues its path
toward the lungs, where it
will supply the blood with
oxygen.
