The epidermis consists of five layers of cells, each layer with a distinct role to play in the health, well-being, and functioning of the skin. Which of the following layers is responsible for cell division and replacement?

A) stratum basale
B) stratum granulosum
C) stratum lucidum

A) stratum basale.

Explanation:

The epidermal layer consists of five layers. This is not having any blood vessels and known as avascular. The four-layer starting from stratum basale to stratum corneum is referred to as thin skin. But the skins of foot and palm has another layer called stratum lucidum. This layer forms the five layers of the epidermis.

The stratum basale is the deep layer of the epidermis. Below this layer dermis is present. This layer consists of basal cells which are precursors of keratinocyte cells. The stratum basale is a single layer cell and it undergoes continual mitosis. So that this cell produces new cells and these new cells replace the other older cells above it.  

As the basal cells are precursors of keratinocytes, they produce all keratinocytes of the epidermis.  

Two other types of cells are produced from this layer - Merkel cell, and melanocyte. Merkel cells act as touch receptors and melanocytes produce melanin pigments.

b a mature ovary of a plant.