What Is the Skin Made of?

The skin is the largest organ in the body, comprising about 15% of the body weight. The total skin surface of an adult ranges from 12 to 20 square feet. In terms of chemical composition, the skin is about 70% water, 25% protein and 2% lipids. The remainder includes trace minerals, nucleic acids, glycosoaminoglycans, proteoglycans and numerous other chemicals.

The skin consists of three main layers: Epidermis, Dermis and Subcutaneous tissue.
The epidermis has 4  additional distinct layers:  Defined below.
The Stratum Basale,  Stratum Spinosum, Stratum Granulosum  & The Stratum Lucidum

The epidermis

The epidermis is the top most layer of the skin. It is the first barrier between you and the outside world. The epidermis consists of three types of cells keratinocytes, melanocytes and Langerhans cells. Keratinocytes, the cells that make the protein keratin, are the predominant type of cells in the epidermis. The total thickness of the epidermis is usually about 0.5 - 1 mm. At the lowermost portion of the epidermis are immature, rapidly dividing keratinocytes. As they mature, keratinocytes lose water, flatten out and move upward. Eventually, at the end of their life cycle, they reach the uppermost layer of the epidermis called stratum corneum. Stratum corneum consists mainly of dead keratinocytes, hardened proteins (keratins) and lipids, forming a protective crust. Dead cells from stratum corneum continuously slough off and are replaced by new ones coming from below. The skin completely renews itself every 3 - 5 weeks. Most mild peels work by partly removing the stratum corneum and thus speeding up skin renewal.
Another significant group of cell in the epidermis are melanocytes, the cells producing melanin, the pigment responsible for skin tone and color. Finally, Langerhans cells are essentially a forepost of the immune system in the epidermis. They prevent unwanted foreign substances from penetrating the skin.
The condition of epidermis determines how "fresh" your skin looks and also how well your skin absorbs and holds moisture. Wrinkles, however, are formed in lower layers.

The dermis

The dermis is the layer responsible for the skin's structural integrity, elasticity and resilience. Wrinkles arise and develop in the dermis. Therefore, an anti-wrinkle treatment has a chance to succeed only if it can reach as deep as the dermis. Typical collagen and elastin creams, for example, never reach the dermis because collagen and elastin molecules are too large to penetrate the epidermis. Hence, contrary to what some manufacturers of such creams might imply, these creams have little effect on skin wrinkles.

There is a moisturizing oil (emu oil ) that penetrates all 7 layers of the skin!

It works because emu oil is almost 100% triglyceride lipid. Triglycerides (a type of fatty compound) are abundant in human skin lipids, meaning that the composition of fatty acids in human skin is very similar to that of emu oil. This makes the absorption of emu oil into human skin faster and more effective.
 
It is high in oleic acid, which increases its ability to carry compounds through the skin.

It does not contain phospholipids, which make absorption more difficult.

This absence of phospholipids makes emu oil highly penetrating and allows it to absorb
through the skin more easily.

CLICK BELOW TO VISIT OUR Ebay STORE and CHECK OUT:
OUR PRODUCTS CONTAING EMU OIL and other great skin care items.........

CLICK HERE TO READ MORE ABOUT THIS STORE OWNER...

The dermis is the middle layer of the skin located between the epidermis and subcutaneous tissue. It is the thickest of the skin layers and comprises a tight, sturdy mesh of collagen and elastin fibers. Both collagen and elastin are critically important skin proteins: collagen is responsible for the structural support and elastin for the resilience of the skin. The key type of cells in the dermis is fibroblasts, which synthesize collagen, elastin and other structural molecules. The proper function of fibroblasts is highly important for overall skin health.

The dermis also contains capillaries (tiny blood vessels) and lymph nodes (depots of immune cells). The former are important for oxygenating and nourishing the skin, and the latter -- for protecting it from invading microorganisms.

Finally, the dermis contains sebaceous glands, sweat glands, hair follicles as well as a relatively small number of nerve and muscle sells. Sebaceous glands, located around hair follicles, are of particular importance for skin health as they produce sebum, an oily protective substance that lubricates and waterproofs the skin and hair. When sebaceous gland produce too little sebum, as is common in older people, the skin becomes excessively dry and more prone to wrinkling. Conversely, overproduction or improper composition of sebum, as is common in adolescents, often leads to acne.

Subcutaneous tissue

Subcutaneous tissue is the innermost layer of the skin located under the dermis and consisting mainly of fat. The predominant type of cells in the subcutaneous tissue is adipocytes or fat cells. Subcutaneous fat acts as a shock absorber and heat insulator, protecting underlying tissues from cold and mechanical trauma. Interestingly, most mammals lack subcutaneous tissue because their fur serves as a shock absorber and heat insulator. Sweat glands and minute muscles attached to hair follicles originate in subcutaneous tissue.

The loss of subcutaneous tissue, often occurring with age, leads to facial sag and accentuates wrinkles. A common procedure performed by dermatologists to counteract this process is to inject fat (collected elsewhere in the body) under the wrinkles on the face.

The "Keratinizing System" of Skin
The vast majority of cells in the skin are keratinocytes. These cells are produced by constant mitosis in the deeper regions. With time they move up to the surface, die, and are worn away, to be replaced by the next wave of newly-produced cells. The life of a given keratinocyte is about 7 to 10 days from production to sloughing.

Other cell types are present in the epidermis, and we'll look at them later, but for now we will be concerned solely with keratinocytes and their fate. The epidermis has several distinct layers, all in well-defined stages of keratinocyte life history. The keratinocytes begin as viable, dividing cells, and end as nothing more than flattened, battered, dead sacs of keratin.

Stratum Basale

The deepest layer of the epidermis is the stratum basale. This is the single layer of keratinocytes, those right up against the derma-epidermal boundary. It's here that almost all of the proliferative activity occurs. This layer is only one cell deep, by definition.

Stratum Spinosum

  One level up from the stratum basale, you will find the stratum spinosum, sometimes called the "prickle cell" layer. In this layer the cells are still alive, but they have a peculiar appearance in LM preparations: there are what appear to be spines or "hairs" protruding out from them, and connecting them to adjacent cells. With high magnification you'll be able to make out these structures, historically called "intercellular bridges" which are characteristic of this layer.

For many years these were believed to represent true communicating structures, but with the development of improved EM tissue techniques, this concept was shown to be incorrect. There is no cytoplasmic continuity between the adjacent keratinocytes of the stratum spinosum.

The "bridges" are actually the sites of dermatomes, by which the adjacent cells of the skin are held together. The dermatomes themselves can't be seen with a light microscope. But after fixation they remain adherent, so that post-mortem shrinkage of the tissue causes stretching of cellular material at these points. Thus the illusion of "bridges" is created. The stratum spinosum may be quite extensive in thick skin, but in thin skin it may be only one or two cells breath.

Stratum Granulosum

Moving again upwards, the next layer is the stratum granulosum. This layer takes its name from the granular pre-keratin material usually seen in its keratinocytes. This material takes the form of aggregated keratohyaline granules. Cells of the stratum granulosum are dead and can no longer divide.
The stratum granulosum is not uniform in distribution. Especially in thin skin, it may be missing altogether. It's usually found in thick skin without trouble. The presence of the granules is not required for keratinizing to occur.

Stratum Lucidum

In thick skin, a stratum lucidum may be visible. You'll see it as a clear band above the stratum granulosum. The stratum lucidum is found only in thick hairless skin. The cells in this layer are dead.
Stratum Corneum & Stratum Disjunctum

At the surface, the outermost layer is found. This is the stratum corneum or "horny layer." It's the actual interface between the outer surface of the animal and its environment. It's the layer where cells are cast off in the normal process of wear and tear.

The very outermost portion of the stratum corneum is constantly in the process of sloughing off. From time to time you may see a reference to the "stratum disjunctum," and that's what is meant by the term. Socially speaking, it's incipient dandruff.

I do hope that this info has been helpful.

Kind Regards,
Terri L Watts
President, Direct2uWholesalecom