Stratified Squamous epithelium
- keratinized
§Formed of
multiple layers of cells. The topmost layer is formed of squamous cells.
The epithelium is covered with keratin (a non-living material).
§
§It’s
found in areas that require protection:
- Skin à Epidermis
§Function:
1) Stratification à protection
2) Keratin à prevent water loss
Stratified Squamous epithelium
– Non-keratinized
§Formed of
multiple layers of cells. The topmost layer is formed of squamous cells.
The epithelium is not covered with keratin.
§
§It’s
found in areas that require protection and water loss is not a problem:
- Mouth, esophagus, anal canal
- Vagina
§Function: protection, secretion.
Stratified Cuboidal and
Columnar epithelium
qThese are
rare in the body. They’re formed of several layers of cuboidal and
columnar cells respectively.
§
qFound in:
- Columnar: Conjunctiva
- Cuboidal: Lining
of large excretory ducts of salivary and sweat glands.
qFunctions: protection and secretion
Transitional
epithelium (Urothelium):
vThe
topmost cells of this stratified epithelium are dome-like (also called umbrella
cells).
v
vFound in:
Urinary bladder, ureters and
renal calyces.
v
vThe
umbrella cells are dome-shaped when the bladder is empty. Once it’s full, these
cells will become flattened (hence the name transitional).
v
Functions: protection against the adverse
effects of urine. Allow the bladder to change size
Pseudostratified columnar ciliated epithelium:
ØIn this
epithelium, the cells have different heights. All
cells rest on the basal lamina, but not all of them reach the surface. This
makes the nuclei occupy different levels giving the epithelium a false
stratified appearance.
Ø
ØFound in
trachea, bronchi and nasal cavity.
Ø
ØFunctions: protection, secretion. Ciliary movement
remove particles from the airway passages.
