What does your skin do?
Your skin is the largest organ of your body. It is composed of living and dead
layers. It protects your body against heat, light, and injury. Your skin is
a major contributor to our immune system: it is our first line of defense to
ward off bacteria, viruses and other potential invaders, and contains large
quantities of T-lymphocytes (T-cells) which attack and destroy bacteria, fungi,
viruses, parasites, toxins and cancer cells that cause disease. It stores water,
fat and vitamin D and provides a waterproof protective covering for the body's
complex internal environment. It also plays a key role in helping to maintain
the circulatory and nervous system.
Our skin is made up of two main layers, the epidermis and the dermis.
The epidermis, or top layer is as thin as a sheet of paper. This layer contains
no nerves or blood vessels and is therefore incapable of sensation or bleeding.
The epidermis contains mainly two types of cells:
Melanocytes are pigment-forming cells that give skin its color. These cells
are located at the base of epidermis and contain the protein, melanin. It is
the amount of melanin that determines a persons skin color. Generally, the more
melanin, the darker the skin.
Keratinocytes contain the protein keratin. They form at the bottom of the epidermis
but migrate to the surface to displace older, dying cells. These dead skin cells
flake off or are washed away but before they do, they contribute greatly to
the outer barrier of the skin.
The Dermis, or inner layer is about as thick as 15-40 sheets of paper. It is
located just below the epidermis on most of the body. It is composed mostly
of connective tissue called "collagen." The bulk of the skin's composition,
this layer contains blood vessels, nerves, sweat glands, and hair follicles.
The inner layer produces sweat which helps cool body and aids body in expelling
nitrogen containing waste and sodium chloride. It also produces oils, which
keep skin from drying out.
The Subcutaneous tissue lies below the Dermis. It is composed of fat cells,
blood vessels and nerves. This fatty tissue performs double duty by acting as
a shock absorber and energy store.
How each UVR penetrates (A,B,C) skin and what it does
UVB rays represent less than 1% of the sun's energy that reaches the surface.
UVB rays are more prevalent in summer. They are more energetic than UVA and
cause sunburn much faster. UVB rays are the major cause of skin cancer. UVB
light only reaches the outer layer of the skin (epidermis).
Although they work slower than UVB rays, UVA rays are 100-1000 times more abundant
(depending on season) and, according to recent research, may be more harmful
than UVB rays. UVA rays penetrate to the inner layer (dermis) of the skin, where
it can damage blood vessels, DNA, and compromise the skin's physical support
Damage and Effects
Overexposure to UVA and UVB rays cause damage leading to wrinkles, lower immunity
against infection, aging skin disorders, and skin cancer.
Overexposure to both UVA and UVB stimulates melanocytes to produce extra melanin
- tanning, or darkening, the skin. Contrary to what we used to think, a tan
is not a sign of good health but, rather, a defense mechanism to protect the
skin from the sun.
Actual sunburn occurs when the body receives excessive amounts of radiation.
Blistering indicating a second-degree burn.
How Skin becomes cancerous
The term "skin cancer" is used to refer to a group of over 100 diseases.
Normal, healthy body cells grow, divide, or replace themselves at maintainable
rates. When cells lose the ability to control or direct their growth, they grow
without order and multiply quickly. As a result, too much tissue is created
and tumors form. These tumors can either be benign or malignant.