The structure of your skin can be simplified by three major parts: The top part is the epidermis, about one tenth of a millimeter thick (at the face), that composes of about twenty layers of skin cells calledkeratinocytes. It makes the outermost protection for the body from the environment. The lower part is the dermis, about a millimeter thick (at the face), that compose of connective tissue that makes the mechanical strength of the skin. The lowest part is the subcutaneous tissue. It is a layer of fat and connective tissue that houses larger blood vessels and nerves. This layer is important for the regulation of temperature of the skin itself and the body.
In the epidermis, keratinocytes are arranged in layers that recapitulate their programmed life cycle. The cells regenerate on the bottom-basal layer, differentiate as they leave and move upward, and finally terminate to form the outermost cornified layer to protect the skin from water loss and external invasion. Melanocytes in the basal layer make pigment melanin sending to keratinocytes to protect cell nucleus from sun radiation.
Illustration of skin cell concepts
In the dermis, fibroblasts make connective tissues such as collagens, glycosaminoglycans, reticular and elastic fibers that account for the firmness of the skin. Other cells in the skin have immune function and work together with keratinocytes and fibroblasts to protect the body from the inhospitable environment. The epidermal-dermal junction is a dynamic structure for communication between cells and tissues in the epidermis and dermis.
The length of cell lifespan depends on the amount of work that the cell performs. These skin cells have the ability to regenerate to replace the dead cells. The total number of cell regeneration is programmed according to the organism’s lifespan. Intrinsic or extrinsic factors that overload the cell’s functional capacity will shorten its lifespan and speed up the cell division frequency to compensate for cell lost, that over years will use up the total number of cell regeneration resulting in skin premature aging.
MODERN SKIN CELL THEORIES
DERMASTEMCELLS Theory - Renew/Repair: Multipotent stem cells in the skin have the capacity for self-renewal and differentiation to various skin cell types, i.e., ketatinocytes and fibroblasts to renew the proliferating cell reservoir and repair the damaged cells. The number of stem cell regeneration is programmed according organism’s lifespan. Abnormal stem cell function can lead to premature aging and other complex skin problems. Healthier skin stem cells could prevent early aging.
ALL CELL COMMUNICATION Theory - Survival: Cells in skin constantly communicate to one another to perform their functions, to mature, and to survive in response to signals and insults from intrinsic and extrinsic environment. Cell communication failure can lead to premature aging and other complex skin problems, thus suggests solutions for problems.
MULTIPLE HITS Theory - The causes/the solution: Thousands of molecules exist in a cell to ensure the operation inside cells and communication between cells to occur properly. Cells defend against insults from environment via adaptive and compensatory mechanisms. Multiple hits (attacks) to many molecules or cellular pathways exceed this defend capacity will shorten cell lifespan and/or cause complicated skin problems. Correction at multiple steps could resolve the problems.