A Little Skin Biology
It’s hard to realize that skin is an organ. In fact it’s the largest organ of the human body
called the integumentary system. It protects the internal organs, as well as muscles
bones and ligaments. Our skin forms a protective barrier against the environment. It
blocks our internal bodies for us against germs and other organisms from getting inside.
It is the skin that helps keep our body temperature regulated.
An average adult has 18 to 20 square feet of skin covering their bodies. It weights
approximately 6 pounds. One square centimeter of skin is made up of 6 million cells.
Skin on the human body has 5,000 sensory points. It consists of 100 sweat glands
located throughout the skin system and 15 sebaceous glands. Human skin is about 0.07
inches or approximately 2mm thick.
Skin is composed of 3 primary layers with multiple sublayers. The outer most layer is
the Epidermis, the middle layer is the Dermis which also includes connective tissue and
the Subcutaneous or Hypo-Dermis is the bottom layer. The Epidermis is a tough
protective layer that contains the melanin. It is melanin that gives us out color and
helps protect us against the damaging sun rays.
The second layer found under the
Epidermis is the Dermis which contains nerve endings, sweat and oil glands and hair
follicles. The Hypo Dermis is the layer that is comprised of adipose (fat) tissue as well as
the blood vessels.
Human skin constantly regenerates itself. To start the process of regeneration; a cell is
generated in the dermis of the skin first. The same cell migrates up towards the
Epidermis over a two week traveling period. At the end of the two weeks it will reach
the bottom layer of the Epidermis.
This cell continues moving until upward until it
reaches the surface of the Epidermis. It spends two more weeks in the Epidermis
flattening out where it eventually dies and sheds. The process of cellular migration from
the Dermis to the Epidermis repeats over and over again. It is a continuous process that
occurs our whole lives. We shed two to three billion skin cells on a daily basis.
The human body goes all out to replace cells as they shed on a monthly basis. This is
because the skin is the first line of defense against dehydration, infection, injury and
extremes of temperature. The skin is an unbroken surface that protects things from
entering the body or penetrating and going throughout our systems.
Skin cells detoxify
harmful substances that try to enter our bodies much in the same way the liver does.
They both filter and help our bodies remove the toxins so the toxins can be eliminated
as waste. Skin can also absorb and utilize nutrients that are topically applied to it. Lets
look at each layer now independently.
The Epidermis
This is the skin layer between you and the external world. It consists of three types of
cells. The total thickness of the epidermis is between 0.5 to 1 mm. The cells of the
Epidermis are keratinocytes, melanocytes and Langerhans cells. The keratinocytes are
the predominant cells in the epidermis and make up the protein Keratin. At the lowest
layer of the epidermis are immature keratinocytes that keep dividing. As the cells divide
they lose moisture and flatten out; all the while moving upward towards the outer most
layer of the Epidermis . The outer most upper layer of the Epidermis is called the
Stratum Corneum
At the end of their life span the cells reach the outer most layer of the epidermis where
they die. This layer is made up of primarily dead keratinocytes, keratin (which is
hardened protein) and lipids which together form a protective crust. The dead cells
from this outer most layer constantly slough off only to be replaced with the ones that
come to the surface. Skin completely renews its self every 3 to 5 weeks.
Melanocytes are the cells responsible for producing melanin which is the pigment
responsible for our skin tones and color. The more melanin in our skin the darker we
are. Genetics also play a part in our skin tones.
The Langerhans are responsible for our immunity through the skin. They are the ones
that prevent unwanted substances from penetrating our skins and entering our bodies.
How we treat our Epidermis shows to the world how young we look as a result.
Although wrinkles develop on the lower skin levels, how fresh we look is based on the
epidermis. The epidermis is the layer that helps hold and absorb moisture to keep us
looking young.
The Layers of the Epidermis
As I mentioned previously the Epidermis is made up of sub layers. We already looked at
the stratum corneum or outer most layer. That layer is made up of dead cells and
protein. The stratum corneum layer has a buildup of the protein Keratin. Keratin is the
protein that is important to skin, nails and hair.
Translucent or transitional layer- This is a translucent thin layer of cells. Sometimes this
layer is seen in thick skinned people.
Suprabasal layers- 3 to 5 layers of flattened cells. Below them are cubed shaped cells
containing little pieces of keratin traces.
Basal or cell division layer- this is the layer where the cells undergo division to travel to
renew and replenish the upper layers. This is the bottom most layer of the Epidermis.
Next we have the Dermis Level.
This is the middle layer located between the Epidermis
and Subcutaneous tissue. This is the thickest of the skin layers. It is made of tight
meshed collagen and elastin fibers. These two elements are crucial skin proteins.
Collagen is a protein that is responsible for structural support and elastin for skin
resilience.
