Amazing Skin - The Body’s Largest Organ

The human skin, that most marvelous of organs, accounts for between fifteen and twenty percent of an average adult’s body weight.  Each square centimeter contains around 6 million cells, 5,000 sensory points, 00 sweat glands and 5 sebaceous glands. 

Our skin is our first line of defense against dehydration, temperature extremes, injury, and infection.  Skin cells have the ability to detoxify harmful substances that come into contact with the outer surface. The skin stores water, fat, and vitamins. The unbroken surface of the skin also prevents infectious organisms from penetrating into systemic circulation.  Some 2-3 billion skin cells are shed daily, with the entire surface being renewed every three to five weeks. 

Taking a Closer Look

Most of us take our skins for granted until a rash, wrinkle, excessive dryness or oiliness stirs our attention.  Taking the time to understand some of the characteristics of skin and how this remarkable organ functions will certainly make us more aware of how we care for our skin and what we can do to keep it in prime condition.

Skin characteristics, such as thickness and density of hair follicles, vary according to what part of the body it covers, but essentially skin consists of three layers, each with its special functions: the Epidermis, the Dermis, and the Subcutaneous layer.

THE EPIDERMIS  

The thin outmost layer, between 0.5-.0 mm thick, is comprised of three sub-layers and contains three types of cells types of cells:  keratinocytes, melanocytes and langerhans cells:

• The status corneum (horny layer) made up of continually shedding, dead keratinocytes (the primary cell type of the epidermis), hardened proteins (keratins) and lipids, forming a protective crust.   Keratin, a protein formed from the dead cells, protects the skin from harmful substances.
• The keratinocytes (squamous cells)
  This layer contains living keratinocytes (squamous cells), which help provide the skin with what it needs to protect the rest of the body, and
• The basal layer, which is the inner layer of the epidermis, consisting of basal cells, which continually divide to form new keratinocytes to replace the old ones that are shed from the skin's outer surface. 

The epidermis also contains melanocytes, specialized cells that produce melanin, which determine skin tone and color.  The third type of cells in this layer are the langerhans cells which are essentially the first defense of the immune system as they prevent unwanted foreign substances from penetrating the skin.

Speeding up the Process of Skin Renewal 

Exfoliation, whether done as part of a beauty regime or in a spa facility, acts by removing the dry, damaged and dead cells of the status corneum and exposing newly formed skin cells.  This generally results in a fresher, smoother skin surface.

Surface nutrition, such as water, moisturizing creams, or skin lotions containing supplements, feeds the cells of this basal layer to encourage new cell production.

THE DERMIS

This middle layer of the skin is the thickest of the three layers and is made up of a strong mesh of collagen and elastin fibers.  Collagen and elastin are crucially important skin proteins.  Collagen is responsible for the skin’s 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 functioning of fibroblasts is highly important for overall skin health. 

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

Hair follicles and sweat glands are also located in this layer, as well as pain and touch receptors.  Sebaceous glands, which are located around hair follicles (see diagram), are of particular importance for skin health as they produce sebum, an oily protective substance that lubricates and waterproofs the skin.  When sebaceous glands produce too little sebum (common in ageing) the skin becomes excessively dry and more prone to wrinkling. Overproduction or improper composition of sebum (common in adolescents) often leads to acne. 

Since wrinkles form and develop in the dermis, no anti-wrinkle treatment has a chance of working unless it can reach the dermis level.  Common creams containing collegen or elastin applied to the skin’s surface don’t usually reach the dermis because their molecules are too large to penetrate the epidermis layer.  Various sophisticated injection techniques have been developed to deliver replenishing collagen or elastin into the correct skin layer.

THE SUBCUTANEOUS LAYER

This lowest layer consists of a network of collagen and fat cells which helps hold in body heat and protects internal organs from injury by acting as insulator and shock absorber.  Sweat glands and networks of tiny muscles originate in this fatty layer. 

A cell is first formed in the dermis, which is supplied with blood vessels and nerve endings.  The cell migrates outward for about two weeks until it reaches the lower area of the epidermis which doesn't have blood vessels but does have nerve endings.  The cell spends another two weeks in the epidermis, gradually losing water, flattening out and continuing to move toward the surface where it dies and is shed.

Since the dermis and the subcutaneous layer contain many nerve endings, the skin is also a sensory organ. The nerves located throughout these layers transmit tactile perceptions to the brain. 

The diminishing of subcutaneous tissue which occurs with age leads to a relaxing of facial skin and an accentuation of wrinkles.

Amazing - But Also Vulnerable

The skin is a powerful a neuro-immuno-cutaneous-endocrine network which acts an interface between the mind, the body, and the external world.   Physical or emotional stress can interfere with the protective functions of the epidermis and can also activate immune or inflammatory reactions deeper within the skin.   

The skin also plays a critical role in the body’s immune system, packed with specialized white cells that gobble up invading microbes and trigger immunologic responses throughout the body.  Because it cannot completely discriminate, the skin may absorb synthetic chemicals or allergens present in the modern environment which can be toxic or irritating.

The middle layer �" the dermis - is particularly vulnerable to the damaging rays of the sun.  The epidermis reacts with pigment-producing melanocytes to deflect penetration to the dermis �" creating a tanning effect. 

Women’s skin is thinner than men’s and less oily so they are more prone to drying and wrinkling and are more sensitive to exposure to the sun and pollutants. Women also sweat less than men and so have less control over high temperatures

Sex hormones also have an affect on the skin. Estrogen increases collagen and skin moisture and promotes wound healing, while testosterone stimulates oil production. Men benefit from both hormones, since skin is able to convert testosterone to estrogen. Women, too, benefit from both, since ovaries produce a small amount of testosterone. When menopause sets in the loss of sex hormones contributes to wrinkles, sagging, and other ageing symptoms. Estrogen-deprived skin becomes thinner, loses collagen, and slows down its cell renewal process. 

Appreciate and Care For Your Skin

Truly, your skin is the most obvious outward and visible sign of your inner health and well being.  A fresh, youthful complexion with a smooth and healthy glow contributes to your spiritual as well as to you physical condition. 

Understanding how your skin functions and learning more about how to care for and preserve it can greatly increase your quality of life.