Question

Outermost skin layer or stratum corneum of frog consist of
A. Columnar non-keratinised cells
B. Flat keratinised cells
C. Flat non- keratinised cells
D. Columnar keratinised cells

Answer 1

Stratum corneum also called horny layer. It is composed of dead keratinised cells. These cells are known to regenerate as they are epidermal cells.

Complete answer:
The stratum corneum is the final layer which consists of epithelial cells that are dead cells, also called corneocytes. These cells are known to perform protective and adaptive physiological functions, this includes, water flux and hydration regulation, mechanical shear, etc. It has 15-20 layers of flattened cells that have no nuclei or cell organelles.

It functions as a barrier protecting underlying tissues from infection, dehydration and mechanical stress. The outermost layer of skin in frogs is the stratum corneum and it has thin layered fertilized cells. Frogs are subjected to water loss via evaporative dehydration. The ventral skin in the frog is the main route of water intake.

-Columnar non-keratinised cells are present in the deep layer. It bears a mucous membrane which has protective function and lubricates the epithelium. It is found in pharynx.
-Flat non- keratinised cells-It acts as a basement layer. It provides structural integrity.
-Columnar keratinised cells- It protects from physical abrasions. It is an important part of the epidermis.

Additional Information: The dense network of keratin is present in the stratum corneum. The stratified columnar epithelial cells are rare. They are located inside eyelids, areas of tissue transition. These cells are responsible for protection and mucus secretion. The columnar keratinized cells lie in the stratified squamous epithelium. These cells are present in the basal layer which is columnar in shape.

Therefore, the correct answer is option ‘B’ i.e, Flat keratinised cells.

Note: The stratum corneum is permanent in reptiles. These are replaced during a rapid growth process called moulting or ecdysis. In this layer there is beta keratin that provides rigidity to the skin layer. Keratin is a protein that helps to keep skin hydrated by preventing water evaporation.