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The Skin, the body's largest organ, is a
magnificent, complex, multi purpose organ.
More has been discovered about the way the skin functions, and its
components structure, in the last ten years than in the last two
hundreds.
The skin's functions:
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Protects the body against injury, heat & light radiation.
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Helps the penetration of chemical agents and invasion of
microbes & microorganism. |
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Regulates body temperature. |
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Eliminate a number of harmful substances resulting from the
metabolic activities of the intestine & the liver. |
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Secretes hormones & enzymes. |
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Acts as an external sensory organ. |
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Plays an immunological role, by cooperation with langerhans cells. |
The skin's components & structure:
Within one square inch of skin, varying from 1mm to 4mm in
thickness, there are:
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650 sweat glands |
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65 hair follicles |
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19 yards of capillaries |
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78 yards of nerves |
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Thousands of sensory cells, nerve endings & langerhans cells |
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Melanocyte cells |
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Tyrosinase enzymes responsible for producing the melanin |
There are two types of glands housed within the skin:
1- Oil glands 2- Sweat glands
The duct of each oil gland usually opens into one hair follicle, but
in some locations, there maybe more oil glands per follicle,
resulting in greater oil (sebum) secretion in that area.
Each sweat gland begins in the dermal tissue as a coiled end. It
continues as a single excretory tube or duct through the epidermis,
and finally opens on the surface as a very tiny pore.
Cleansing the skin, means eliminating impurities from these pores,
considering that perspiration is not a cleanser.
The Skin's layers:
The surface of the skin is made of a conglomeration of dead cells.
Underneath the surface, there are very thin & distinct layers, which
are called:
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The Epidermis |
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The Dermis |
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The Hypodermis |
The Epidermis:
The Epidermis, which thickness varies from 0-04mm to 1.6mm, is an
important layer. The langerhans cells, responsible for the
immunology of the skin, the melanocytes and tyrosinase enzyme,
responsible for the production of melanin and color, are located in
the epidermis.
This is the layer of skin to which, cleansing, exfoliating or
hydrating products are applied.
Why is Epidermis important?
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It is responsible for the look & the health of the skin. |
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It protects the skin from moisture loss & the penetration of
chemical products and bacteria. |
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It is a metabolically active tissue that synthesizes the lipids. |
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It acts as the initial barrier to oxidant assault. |
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It houses essential free radical scavengers such as vitamins E and
C & super oxide dismutase. |
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It is able to create large amounts of glycosaminoglycans &
ceramides. |
The Epidermis holds a large amount of water. The younger the body,
the more water there is in the skin. The skin's capacity to retain
water decreases with age, making the skin more vulnerable to
dehydration & wrinkles.
The Epidermis is also the first barrier against immunological
aggressors, thanks to the langerhans cells.
Langerhans cells are ultraviolet radiation (UVR) sensitive. Even
minor UVR exposure will damage the langerhans cells enough to reduce
the skin's immune capacities. With age, these cells also decrease in
number, one reason why the elderly have higher potential rates of
skin disease. In the basal sub-layer of epidermis, cells reproduce
by subdivision. One cell divides into two, identical to one another
and to the original parent cell. The older one is pushed upward and
the younger remains. The new cells are large and supple and contain
a high percentage of water. With age, this layer thins, making it
difficult for the skin to retain moisture. As the cells move upward,
they begin to fill with a granular substance called Keratin, lose
water and flatten. Their phospholipids change to glycolipids,
cholesterol & ceramides and then dead cells accumulate on the skin
surface.
Ceramides play a vital role in the skin's water-retaining capacity,
after being damaged from aging and sun exposure.
There is also a natural moisturizing factor (NMF) in Epidermis.
Exposure to harsh detergents & climatic conditions can result in
decreased NMF levels, rendering the skin fragile and dry.
For ageing or damaged skin, ingredients such as alpha hydroxy acids
(A.H.A s) tend to restructure on abnormal skin, giving it a
healthier and normal basket - wave structure.
The Dermis:
The second layer, or dermis which is 5 to 7 times thicker than the
Epidermis, lies below the epidermis and is connected to it by the
basement membrane.
The Dermis consists of a thick connective membrane criss-crossed by
blood vessels, lymphatic vessels, nerve fibers and many sensory
nerve endings.
Collagen and Elastin protein fibers, the two main components of the
dermis, act as a structural support system for the nerve fibers,
hair follicles, blood vessels, and oil and sweat glands located in
this layer, and also provide the skin with strength & elasticity.
Why is Dermis important?
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It nutrites the epidermis by means of its vast network of
capillaries and blood vessels. |
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It forms a supporting framework, composed of collagen & elastin
protein fibers. |
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It is responsible for the skin's elasticity. |
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It acts as a water storage site. |
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It protects the body from mechanical injury. |
It plays an important role in sensory perception and as an internal
regulator.
The Hypodermis:
The Hypodermis, the skin's third and the last layer, connects the
skin with the muscle tissues.
This layer is highly elastic and has fat cells acting as "shock
absorbers", thereby supporting delicate structures such as blood
vessels and nerves.
Differences In Skin Due to Sex:
Most human bodies are very alike and the differences are usually
minor. The skin is no exception. The greatest difference is
attributed to sex and the following observations have been made:
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Chemicals from the male glands increase the thickness of skin and
strengthen the tissue of the dermis. |
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Men's skin is hairier somewhat coarser than women's. |
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Men have more sweat glands since men are larger and have more skin. |
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Male skin cells have a somewhat deeper color due to the greater
amount of melanin in the skin. |
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Men have greater output of sebaceous glands. |
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The chemicals from the female sex glands make skin softer. |
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Women have fewer and shorter body hairs, but the hair on their head
is finer and grows longer. |
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Many men lose hair or their hair grows gray or white and more
sparse. |
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Race has very little effect on people's skin and may indicate only
a slight variation in the distribution of skin glands. |
Dark color is due to specific skin cells and these cells exist in
about the same quantity in all people.
In some groups of people, the cells are larger or produce more
melanin.
Other skin conditions are inherited such as the color of the hair
and the fairness of the skin.
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