Question

Keratinized dead layer of skin is made of
A. Stratified squamous epithelium
B. Simple cuboidal epithelium
C. Simple columnar epithelium
D. Stratified columnar epithelium

Answer 1

Hint: Let’s define tissue first. Tissue is a group of similar or dissimilar cells that perform a specific function. Epithelial tissue is a type of an animal tissue. The cells in this tissue are arranged in a sheet which covers the body surface of the body or lines the body cavity. The epithelium plays an important role in protection, secretion, absorption, filtration, excretion and receives sensory information.

Complete answer:
Most of the epithelial tissues cover all the surfaces of the body which are exposed and lining the outside of organs. Based on the shape of the cells and the number of cell layers formed, the epithelial tissues are classified into simple epithelium and compound epithelium or stratified epithelium. In squamous epithelium cells are flattened and thin, in cuboidal epithelium cells are wide and tall and in columnar epithelium cells are rectangular.
Keratinized dead layer of skin is a type of compound epithelial tissue. It is a stratified squamous epithelium because the cells of this tissue are arranged in many layers (stratified). The shape of cells in different layers are different. The cells of the deeper layers vary from cuboidal to columnar. The superficial layers are flattened (squamous) towards the free surface.
The cells on the surface of stratified squamous are flat and contain fibrous protein called keratin. The keratinized epithelium are dead or no longer living cells. These cells are horny, scale-like remains of dead squamous cells. These dead cells are continually lost from the surface of the skin. These cells are replaced by new cells from the layers below. Keratinized cells are waterproof and highly resistant to mechanical injury.

Thus, option A is the correct answer.

Note: Keratinized dead layer of skin is stratified squamous epithelium and is composed of dead cells due to deposition of keratin. Thus, cells are keratinized. These cells are waterproof and highly resistant to mechanical injury.