Skin Anatomy

the epidermis is the most superficial layer of the skin and provides the first barrier of protection from the invasion of foreign substances into the body. the principal cell of the epidermis is called a keratinocyte. the epidermis is subdivided into five layers or strata, the stratum germinativum (SG), the stratum spinosum (SS), the stratum granulosum (SGR), the stratum lucidum, and the stratum corneum (SC).

the miracle starts in the lower layers of the epidermis, where new cells are continually forming. as they mature, they slowly work their way to the surface, where after becoming depleted of moisture, are sloughed off.

the epidermis is in a constant state of renewal, completely replacing itself every 28 days. the epidermis is the visible layer of your skin - a mere 1/1000 of an inch thick. just think, your whole appearance depends on the visible condition of less than a millimeter of skin.

the dermis assumes the most important functions of the skin - thermoregulation and supporting the vascular network (to supply the vascular epidermis with nutrients). the dermis is typically subdivided into two zones, a papillary dermis and a reticular layer.

the dermis contains mostly fibroblasts which are responsible for making collagen, elastin, and ground substance that give the skin it's support and elasticity. immune cells are also present that are involved in defense against foreign invaders that have gotten through the epidermis.

the skin also contains a variety of appendages, mainly hair follicles, sweat glands, and sebaceous glands. these appendages usually extend deeper into the subcutaneous layer of fat.