Question

Stratified squamous epithelium cells can exist two forms; keratinized and nonkeratinized. Describe these two forms and where they would typcialy be found.

Answer 1

Stratified Squamous Epithelium
This type of epithelium is made up of several layers of cells. The cells of the deepest (or basal)
layer rest on the basement membrane: they are
usually columnar in shape. Lying over the
columnar cells there are polyhedral or cuboidal
cells. As we pass towards the surface of the
epithelium these cells become progressively more
flat, so that the most superficial cells consist of
flattened squamous cells .
Stratified squamous epithelium can be divided
into two types: non-keratinised and keratinised.
In situations where the surface of the epithelium
remains moist, the most superficial cells are living
and nuclei can be seen in them. This kind of epithelium is described as non-keratinised. In contrast, at places where the epithelial surface   (as in the skin) the most superficial cells die and lose their nuclei. These cells contain a
substance called keratin, which forms a non-
living covering over the epithelium. This kind
of epithelium constitutes keratinised stratified
squamous epithelium.
Stratified squamous epithelium (both
keratinised and non-keratinised) is found over
those surfaces of the body that are subject to
friction. As a result of friction the most
superficial layers are constantly being removed
and are replaced by proliferation of cells from
the basal (or germinal) layer. This layer,
therefore, shows frequent mitoses.
Keratinised stratified squamous epithelium covers the skin of the whole of the body and forms the
9 epidermis .Non-keratinised stratified squamous epithelium is seen lining the mouth, the tongue, the pharynx, the oesophagus, the v...agina and the cornea. Under pathological conditions the epithelium in any of these situations may become keratinised.