Question

Which cell is the most abundant in the epidermis?

Answer 1

1. The epidermis is the finely transparent external skin that protects the body. The skin is visible.
2. It does not contain any vessels of the blood and is thus dependent on the Dermis, the skin layer beneath it, for nutrient access and waste disposal.
3. Just the eyelid's thickness is 0.05 mm, and the palms and feet's sole's thickness is 1.5 mm.

Complete answer:
The epidermis is the outermost part of the three layers of the dermis and the internal layers. The epidermis layer creates a barrier to environmental infections, which controls the volume of water that is absorbed into the atmosphere through transepidermal water depletion. The epidermis consists of several layers of flattened cells, which are perpendicular to a base layer (stratum basale). The epidermis layers include the stratum basale (the lowest part of the epidermis), stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum (the most superficial portion of the epidermis)
Keratinocytes are the most common type of cell present in the epidermis, the skin's outermost layer. They account for $90\%$ of epidermal skin cells in humans. Basal keratinocytes are basal cells that reside in the skin's basal layer (stratum basale). Keratinocytes' primary role is to form a shield against environmental damage caused by sunlight, UV radiation, water depletion, pathogenic bacteria, fungi, parasites, and viruses.
Pathogens entering the epidermis' upper layers may cause keratinocytes to release proinflammatory mediators.
The epidermis is composed of 4 to 5 cell layers. It consists of $95\%$ keratinocytes, which are cells that produce and accumulate keratin. Hair, nails, and skin have their hardness and waterproof qualities as a pigment, keratin.

Note:

1. Keratinocytes proliferate in the epidermis's basal layer and begin differentiating as they move to the surface, undergoing incremental differentiation.
2. During this phase, they undergo significant morphological changes and begin to develop keratin, cytokines, growth factors, interleukins, and complement factors.
3. Several influences, as well as epigenetic regulatory pathways, influence keratinocyte differentiation.