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| The
skin is the largest organ of the body and, as such, comprises
a surface area which is subjected to external injury from
mechanical forces (e.g., pressure, friction, shear, stripping),
chemical exposure (e.g., urine, stool, wound exudate, solutions
for skin and wound care), radiation (e.g., ultraviolet,
therapeutic) and potential pathogens (e.g., fungi, bacteria).
Provision of a barrier is one of the skin's primary functions.
Additionally, it prevents dehydration through evaporative
water loss, maintains thermoregulation, synthesizes vitamin
D, and provides sensory feedback. |
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Anatomically, the skin is composed
of two layers: the epidermis and the dermis. The epidermis,
which is the outermost layer of the skin, is characterized
as follows:
- Avascular
- Varies in thickness (depending on body location)
- A dry structure which sheds cells and replaces itself every 4-6 weeks
- Approximately the thickness of a piece of plastic wrap
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The dermis is located directly beneath
the epidermis and is characterized as follows:
- Provides strength and structural support through a vascular network of connective tissues
- Contains blood vessels, nerves, hair, nails, sebaceous glands, and sweat glands
- Is thicker than the epidermis
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| Below the dermis is the subcutaneous
tissue which is composed of major vessels, lymphatics,
fat, and connective tissue. This area provides insulation
and nutritional support for the skin. Located below the
subcutaneous tissue are fascia, muscles, tendons, and
bone. All layers of tissue below the epidermis are moist.
Therefore, moisture retentive wound care treatments are
usually indicated in order to maintain cell life and proliferation. |
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| The skin changes as we age. The number
of sweat glands declines and the epithelial and fatty
layers of the subcutaneous tissue become thinner. As this
padding is lost, a higher risk of skin breakdown secondary
to pressure, friction, stripping, and shearing exists.
Itching and dry skin are also common complaints. Disease
states, dehydration, malnutrition, medications, and immobilization
may further affect the skin and, when a wound is present,
may impair healing. |
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| Variations in skin color based on
ethnic background can lead to a missed diagnosis of early
compromise. Although the epidermal outer layer in black
patients is the same thickness as that of lighter skinned
individuals, there are a greater numbers of cells which
are arranged in a more compact fashion. This results in
a more effective barrier to chemical and mechanical insults.
However, the dark pigmentation also makes assessment of
early injury and treatment more difficult to detect. In
black patients, an "ashy" appearance of the skin, warmth,
tightness, or firmness under the skin are signs of early
compromise. |
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| An in-depth discussion of the skin
is beyond the scope of this material. However, knowledge
of optimal conditions for healthy skin is important to
understanding the rationale for prevention techniques. |
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