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]
Subcutaneous tissue The subcutaneous tissue (from Latin subcutaneous, meaning "beneath the skin"), also called the hypodermis, hypoderm (from Greek, meaning "beneath the skin"), subcutis, or superficial fascia, is the lowermost layer of the integumentary system in vertebrates.[3] The types of cells found in the hypodermis are fibroblasts, adipose cells, and macrophages. The hypodermis is derived from the mesoderm, but unlike the dermis, it is not derived from the dermatome region of the mesoderm. In arthropods, the hypodermis is an epidermal layer of cells that secretes the chitinous cuticle. The term also refers to a layer of cells lying immediately below the epidermis of plants.