Figure 1.

Layers of the skin. Skin consists of numerous cell types organized into 3 primary layers: the epidermis, dermis, and the hypodermis. The epidermis can further be sub-stratified into stratum corneum, granulosum, spinosum, and basalis. The cornified or horny layer (stratum corneum) is the most superficial layer, consisting of dead cells and keratin matrix. Deep to the stratum corneum is the granular layer (stratum granulosum), made up of cells in the process of anucleation and keratin production. Beneath the stratum granulosum lies the spinous layer (stratum spinosum) which anchors the upper and lower layers of the epidermis. The deepest layer of the epidermis is the basal layer (stratum basalis), consisting of a single layer of rapidly dividing columnar or cuboidal keratinocytes sitting atop the basement membrane. Between the epidermis and the dermis is the basement membrane (unlabeled) which maintains adherence between the dermis and epidermis. The dermis is the thick layer beneath the basement membrane. The dermis contains fibroblasts, smooth muscle, nerves, and blood vessels, and provides most of the key physical properties of skin. The hypodermis is the subcutaneous fat layer lying below the dermis.