which layer of the epidermis is responsible for cell division and replacement
Epidermis The stratified squamous epithelium is maintained by cell division within the stratum basale. Differentiating cell delaminate from the basement membrane and are displaced outwards through the epidermal layers, undergoing multiple stages of differentiation until, in the stratum corneum, losing their nucleus and fusing to squamous sheets, which are eventually shed from the surface (desquamation). Differentiated keratinocytes secrete keratin proteins which contribute to the formation of an extracellular matrix and is an integral part of the skin barrier function. In normal skin, the rate of keratinocyte production equals the rate of loss,[4] taking about two weeks for a cell to journey from the stratum basale to the top of the stratum granulosum, and an additional four weeks to cross the stratum corneum.[2] The entire epidermis is replaced by new cell growth over a period of about 48 days.[11]
Dermis The dermis is composed of three major types of cells:[3] fibroblasts, macrophages, and adipocytes.
Epithelium Epithelium lines both the outside (skin) and the inside cavities and lumina of bodies. The outermost layer of human skin is composed of dead stratified squamous, keratinized epithelial cells.[14]
Human skin Epidermis, "epi" coming from the Greek meaning "over" or "upon", is the outermost layer of the skin. It forms the waterproof, protective wrap over the body's surface which also serves as a barrier to infection and is made up of stratified squamous epithelium with an underlying basal lamina.