The Skin

The skin is a remarkable organ -- the largest found in the human body -- with an average size of 18 square feet. Its weight with normal fat is 20 lbs. With age, the amount of under-the-skin fat is reduced, causing a lack of elasticity. Naturally, well-toned, constantly exercised muscles help to retard the collapsing of skin resulting from fat loss.

The Skin forms the boundary between the external world and the internal organs, providing a barrier against the chemical and physical elements of the outside environment. It acts primarily as a protective covering. Skin acts as a net, holding all body structures in place, giving form to the body. It acts as a heat regulator in conjunction with the bloodstream and perspiration glands.

When the body is exposed to too much heat, there is a rush of blood to the surface of the skin, permitting it to cool. At the same time, the perspiration glands excrete their liquid to aid in this process. Transpiration and respiration is constantly taking place through the pores.

Skin also performs other functions, some of which are given below:

Keratinization - is the process by which the skin produces a fibrous protein that forms the outer layer of the epidermal structures, including hair and nails. Sensory perception occurs in the skin, preventing damage to it by its ability to feel heat and/or cold – giving pleasure by the same ability to feel such things as the smoothness of satin or the softness of down.

Melanin - is a dark pigment found in the skin, triggered by light and heat. It is the area where both sebum and perspiration production take place and where these two combine on the surface to form a protective film (Acid Mantle) which renders the skin less vulnerable to damage and attack by environmental factors (e.g. sun, wind, bacteria) and less prone to dehydration.

pH - is the chemist’s term for Potential of Hydrogen and is used to describe the degree of avidity of alkalinity in the avid mantle of the skin or in a product. It is measured on a scale ranging from 0 to 14. The center of the scale, 7, is neutrality (neither acid nor alkaline). A reading above 7 indicates that the substance being measured is alkaline--below 7, acid. As afar as the skin is concerned, a normal pH (or normal Acid Mantel) is in the range of 4.2 to 5.6. It will vary from one part of the body to another and generally speaking, the pH of a man’s skin is lower (more acid) than that of a woman’s.

The Chemical Composition of the Skin:

The skin, and in fact our whole body, is composed of many different types of cells. These cells have the same fundamental chemical composition, but they vary in shape, size and function. The cells that comprise the outer layer of the skin are themselves a series of many layers that overlap each other, thus ensuring that fluids cannot escape from the body via the skin except through a cut or break in the skin, or by means of special escape routes: the pores.

The skin consists of:

1. EPIDERMIS (which in turn has 4 layers: Stratum, Corneum, Stratum Lucidum, Stratum Granulosum, and Stratum Basal.)

2. DERMIS (or true skin)

3. SUBCUTANEOUS TISSUE

As estheticians, however, we are most concerned with the outer layer:

The EPIDERMIS. This does not mean that the DERMIS means nothing to use because everything the epidermis is or can be, is the result of how the dermis behaves (and naturally, the entire system comprising the body.)

EPIDERMIS - is a thin layer averaging about 0.2 mm in thickness, and is that part of the skin where the greatest metabolic activity takes place. Protein keratin is the main component of the Stratum Corneum, or horny layer, and results from the change that takes place when new, live cells are produced in the basal layer and are pushed upward by newer cells until they reach the absolute surface. During this movement, they are keratinized -- dried and sloughed off.

The process of shedding and renewal takes about 30 days (which means that 30 days after a cell is born in the bottom later, it ends up on the surface of the skin, dead and ready to exfoliate.) Skin pigments (melanin) are produced in the basal cell layer.

DERMIS - or true skin contains the vascular bed and peripheral nerves. Additionally, it is composed of connective tissue interspersed with various specialized structures such as hair follicles, sweat and sebaceous glands.

SUBCUTANEOUS TISSUE - provides further support, stores the skin fat and acts as a shock absorber and heat insulator.

SEBACEOUS GLANDS - are clusters of cells that are capable of producing a very special oil sebum -- which is secreted to the surface of the skin via minuscule tubes that terminate on the surface as openings (pores).

The more active sebaceous gland is, the more sebum is produced, and the more it runs through the tube, the more the pore is stretched. Sebaceous Glands also secrete sebum to the surface of the skin where, mingling with perspiration, a film (Acid Mantle) is formed.

This film is slightly acidic and protective. It prevents excessive evaporation of moisture from inside the skin cells and at the same time defends the skin against aggression by outside elements such as bacteria, sun, pollution, etc.

PERSPIRATION or SWEAT GLANDS comprise coils of cells, which produce a watery solution. This is released through long, vertical channels opening into pores at the skins surface.

*Note that Sebaceous Glands do NOT use the same pores as Sweat Glands, but as noted above, the secretions of both glands unite in the skins surface to create the Acid Mantle. The number of things the skin does for us is incredible. It covers us (epidermis and dermis), helps keep us warm (fatty layer), cools us off (sweat glands), keeps itself supple (oil glands), registers our sense of touch (nerves), and is ornamental (hair, eyelashes, nails).

Ref: DDF Professional Product Guide, pgs. 3-6