Skin




-Skin is a soft outer covering of an animal, in particular a vertebrate.
-Skin is composed of two primary layers: The epidermis and the dermis.

The epidermis is the thinnest outermost layer of the skin which provides waterproofing and serves as a barrier to infection.
The dermis is the layer of skin beneath the epidermis which serves as a location for the appendages of skin. It contains blood vessels, nerves, muscles, oil, and sweat glands.
external image skin.jpg
Melanin is a pigment that protects your skin and gives it color.

Your skin provides protection, and eliminates body wastes.

Skin performs the following functions:
  1. Protection: an anatomical barrier from pathogens and damage between the internal and external environment in bodily defense; Langerhans cells in the skin are part of the adaptive immune system.
    Sensation: contains a variety of nerve endings that jump to heat and cold, touch, pressure, vibration, and tissue injury; see somatosensory system and haptic perception.
  2. Heat regulation: increase perfusion and heatloss, while constricted vessels greatly reduce cutaneous blood flow and conserve heat.
  3. Control of evaporation: the skin provides a relatively dry and semi-impermeable barrier to fluid loss.
    Storage and synthesis: acts as a storage center for lipids and water
  4. Absorption: oxygen, nitrogen and carbon dioxide can diffuse into the epidermis in small amounts; some animals use their skin as their sole respiration organ (in humans, the cells comprising the outermost 0.25–0.40 mm of the skin are "almost exclusively supplied by external oxygen", although the "contribution to total respiration is negligible").
    Water resistance: The skin acts as a water resistant barrier so essential nutrients aren't washed out of the body.

    Skin Repair



    The skin produces new cells in its epidermis and repairs tears in the dermis. When skin is injured, disease-causing organisms can enter the body rapidly. A bruise is caused by tiny broken blood vessels underneath the skin. When you cut your skin, blood flows out of the cut until a clot forms, causing a scab to protect against bacteria. Skin grafts can be made from a cadaver or a victim´s healthy skin to repair the epidermis.

    Vitamin D



    Small amounts of this vitamins are produced in the presence of ultraviolet light from a fatlike molecule in your epidermis. Vitamin D is essencial for good health because it helps your body absorb calcium into your blood from food in your digestive tract.