The Skin

Discussion in 'The Universe' started by wallflower, Jun 21, 2014.

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    wallflower

    wallflower Moderator

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    There are 3 layers of skin:

    Epidermis
    Dermis
    Hypodermis (Subcutaneous)

    http://dermatology.about.com/cs/skinanatomy/a/anatomy.htm

    The labels on the diagram are hard on the eyes - I tried zooming in to see more clearly, but the labels are still blurred.

    However, the article describes the layers of the skin in an understandable manner, so I chose it for that reason.

    (I'll come back to this subject - I've got 2 research projects going at once.)

    Wallflower
     
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    wallflower

    wallflower Moderator

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    Epidermis:

    The epidermis is the outer layer of the skin. The top layer of the epidermis (the skin's surface) is called the stratum corneum. If not damaged, the stratum corneum acts as a barrier against water and bacteria. The palms of the hands and the soles of the feet have a thicker stratum corneum. These parts of the body need greater protection.

    The bottom layer of the epidermis is called the basal layer. Skin cells called keratinocytes come from the basal layer. Keratinocytes gradually work their way up to the stratum corneum (skin's surface). When they reach the stratum corneum, they are shed and replaced by the newer cells that have worked their way up through the epidermis.

    Cells called melanocytes are found in the basal layer of the epidermis. Melanocytes make the pigment called melanin, which affects skin colour. The main role of melanin is to filter out UV rays (ultraviolet radiation from sunlight.)

    Langerhans cells can also be found in the epidermis. They help locate foreign substances, fight against infections and are involved in developing skin allergies.

    http://www.merckmanuals.com/home/sk..._skin/structure_and_function_of_the_skin.html

    Wallflower
     
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    wallflower Moderator

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    The dermis layer is located below the epidermis layer.

    The dermis is made of fibrous and elastic tissue such as collagen, elastin and fibrillin. These tissues provide the skin with flexibility and strength.


    The dermis layer contains the following:

    Nerve endings can sense pain, touch, pressure and temperature. The nerve endings relay these messages back to the brain.

    Sweat glands are responsible for producing sweat (made up of water, salt and other chemicals.) The sweat glands do this to alleviate the effects of heat and stress on the body.

    Sebaceous glands make an oil called sebum. The sebum is secreted into the hair follicles. (A hair follicle is where a shaft of hair grows from, in the skin.) The sebum oil provides moisture for the skin and it serves as a barrier against foreign substances entering the body.

    Hair follicles are responsible for producing hair. Aside from making us look good, hair also regulates body temperature, protects against injury and enhances sensation (e.g. like when we feel something brushing against our leg.) Part of the follicle contains stem cells. These stem cells are able to regrow epidermis tissue that has been injured.

    Blood vessels transport nutrients to the skin. They can also assist in regulating body temperature. Heat causes the blood vessels to enlarge. This results in large amounts of blood to be circulated near the skin surface. The body can release heat in this way. Cold temperatures cause the blood vessels to narrow and this allows the body to retain heat.

    http://www.merckmanuals.com/home/ski..._the_skin.html

    Wallflower
     

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