noun, plural: keratinocytes
The skin serves as an outer protective covering of many animals. In particular, the skin of mammals and humans is composed of two major layers: (1) epidermis and (2) dermis. The epidermis is the outer, waterproofed layer of the skin and the dermis is the layer below the epidermis. The epidermis is a stratified squamous epithelium made up mainly of (95%) keratinocytes. The other cells present in the epidermis are Merkel cells, melanocytes, and Langerhans cells.
A keratinocyte is a highly specialized epithelial cell. The (basal) keratinocytes in the deepest layer of the epidermis (i.e. stratum germinativum) divide mitotically to provide new cells for the upper layers of the epidermis. Newly-produced keratinocytes move up and differentiate into anucleated cells forming desmosomes between them. They secrete keratin and lipids that provide mechanical strength to the skin. Keratinocytes (now called corneocytes) on the outermost layer of the epidermis (i.e. stratum corneum) are regularly shed through desquamation.
The keratinocytes, therefore, play a major role in providing a protective barrier against infective agents, environmental damage, and water loss. They are also involved in the local immune response against antigens that gained entry to the skin. They release chemokines (e.g. CXCL10 and CCL2) that attract leukocytes to the site.
Word origin: keratin- + -o- + -cyte ("cell")
- skin cell