Anatomy of the Skin
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Most Important Function
• PROTECTION is the
most important
function of the
integumentary system
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5 Major Functions
1. Serving as a barrier against
infection and disease
2. Helping to regulate body
temperature
3. Removing waste products
from the body
4. Providing protection
against Ultraviolet radiation
from the sun
5. Producing vitamin D
3
Layers of Skin
• Epidermis
• Dermis
• Subcutaneous layer
• beneath dermis
• not part of skin
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Subcutaneous Layer
• hypodermis
• loose connective tissue
• adipose tissue
• insulates
• major blood vessels
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Epidermis
• lacks blood vessels
• keratinized
• thickest on palms and soles (0.8-1.4mm)
• melanocytes provide melanin
• rests on basement membrane
• stratified squamous
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Epidermis
• Outermost layer of the skin
• Its layers are made of Mostly DEAD CELLS.
• Most of the cells of the epidermis undergo rapid
cell division (MITOSIS).
• As new cells are produced, they push older cells to
the surface of the skin. The older cells become
flattened, lose their cellular contents and
begin making KERATIN.
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Keratin
• A TOUGH FIBROUS PROTEIN that FORMS THE
BASIC STRUCTURE OF HAIR, NAILS, AND
CALLUSES.
• Eventually, the Keratin-producing Cells
(KERATINOCYTES) DIE AND FORM A TOUGH,
FLEXIBLE WATERPROOF COVERING ON THE
SURFACE OF THE SKIN. Our thickest Epidermis
is on palms of hands and soles of feet.
• OUTER LAYER OF DEAD CELLS IS SHED OR
WASHED AWAY ONCE EVERY 14 TO 28 DAYS.
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Epidermis
Layers of Epidermis
• stratum corneum
• stratum lucidum
• stratum granulosum
• stratum spinosum
• stratum basale
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5 Layers of Epidermis
• From superficial to
most deep
• Stratum corneum
• Stratum lucidum
• Stratum granulosum
• Stratum spinosum
• Stratum basale
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Dermis
• on average 1.0-2.0mm thick
• contains dermal papillae (fingerprints)
• binds epidermis to underlying
tissues
• irregular dense connective tissue
• muscle cells
• nerve cell processes
• specialized sensory receptors
• blood vessels
• hair follicles
• glands
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Hair Follicles
• epidermal cells
• tube-like depression
• extends into dermis
• hair root
• hair shaft
• hair papilla
• dead epidermal cells
• melanin
• arrector pili muscle
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Nails
• protective coverings
• nail plate
• nail bed
• lunula
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Sebaceous Glands
• usually associated with hair
follicles
• holocrine glands
• secrete sebum (oil)
• absent on palms and soles
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Sweat Glands
• sudoriferous glands
• widespread in skin
• originates in deeper dermis
or hypodermis
• eccrine glands
• apocrine glands
• ceruminous glands
• mammary glands
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Sensory structures of Dermis
•
•
•
•
•
Deep touch/pressure: Pacinian corpuscles
Light touch/pressure: Meisner’s corpuscles
Warm temperature: Free nerve endings
Cold temperature: Free nerve endings
Pain: Free nerve endings
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Regulation of Body
Temperature
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Problems in Temperature
Regulation
Hyperthermia – abnormally high body temperature
Hypothermia – abnormally low body temperature
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Regulating body temperature
• The dermis helps us to control our body
temperature:
• On a cold day when the body needs to conserve
heat, the blood vessels in the dermis NARROW.
• On hot days, the blood vessels WIDEN, warming
the skin and increasing heat loss.
• Tiny muscle fibers attach to hair follicles contract
and pull hair upright when you are cold or afraid,
producing what is commonly called Goose
Bumps.
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Skin Color
Genetic Factors
Physiological Factors
• varying amounts of
• dilation of dermal blood
melanin
vessels
• varying size of melanin
• constriction of dermal blood
granules
vessels
• albinos lack melanin
• accumulation of carotene
• jaundice
Environmental Factors
• sunlight
• UV light from sunlamps
• X rays
• darkens melanin
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Skin Color
• The Epidermis contains MELANOCYTES, cells that
produce MELANIN, a dark brown pigment.
• Both light skinned and dark skinned people have
roughly the same number of melanocytes, the
difference in our skin color is caused by the amount
of melanin the melanocytes produce and distribute.
• The amount of melanin produced in skin depends on
TWO factors - Heredity and the Length of Time the
Skin is Exposed to Ultraviolet Radiation (Tanning).
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Skin Color
• Melanin is important for protection, by absorption
of Ultraviolet Radiation from the sun. All people,
but especially people with light skin, need to
minimize exposure to the sun and protect
themselves from its Ultraviolet Radiation, which
can damage DNA in skin cells and lead to deadly
forms of skin cancer such as MELANOMA
CANCER.
• THERE ARE NO BLOOD VESSELS IN THE
EPIDERMIS, WHICH IS WHY A SMALL
SCRATCH WILL NOT CAUSE BLEEDING.
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Melanocyte
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Melanocyte
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Melanoma
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Actinic Keratosis
Caused by sun damage. Can lead to
squamous cell carcinoma.
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EVOLUTION OF SKIN COLOR
• Balance between
– Need for protection against UV radiation which
Causes skin cancer
Destroys folate (vitamin B)
– Need for UV to produce vitamin D for calcium
absorption
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Healing of Cuts
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Healing of Burns
First degree burn – superficial partial-thickness
Second degree burn – deep partial-thickness
-burns some dermis
-fluid escapes from capillaries and builds up
under epidermis causing blistering
Third degree burn – full-thickness
• autograft (own skin transfer)
• homograft (person to person [cadaver])
• various skin substitutes
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First Degree Burn
• Only the superficial
epidermis is burned,
and is painful but not
blistered.
• Causes death of
epidermal cells.
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Second Degree Burn
• Deeper layers of
epidermis are effected
– And touches dermis
• Could have
inflammation, blisters,
and the burned skin is
often painful.
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Third Degree Burn
• The entire epidermis is
charred or burned away,
and the burn may extend
into the dermis.
• Often such a burn is not
painful at first, if the
receptors in the dermis
have been destroyed.
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Life Span Changes
• Skin becomes scaly
• Age spots appear
• Epidermis thins
• Dermis becomes reduced
• Loss of fat
• Wrinkling
• Sagging
• Sebaceous glands secrete
less oil
• Melanin production slows
• Hair thins
• Number of hair follicles
decrease
• Nail growth becomes impaired
• Sensory receptors decline
• Body temperature unable to be
controlled
• Diminished ability to activate
Vitamin D
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Clinical Application
Acne Vulgaris
•most common skin disorder
•sebum and epithelial cells clog glands
•produces whiteheads and blackheads
•anaerobic bacteria trigger inflammation (pimple)
•largely hormonally induced
•androgens stimulate sebum production
•treatments include antibiotics, topical creams, birth control pills
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Common Skin Disorders
• If the Ducts of Oil Glands become clogged with excessive
amounts of Sebum, Dead Cells, and Bacteria, the Skin
disorder ACNE can result.
• When first wearing new shoes, the skin of the foot may be
subject to friction. This will separate layers of Epidermis,
or separate the Epidermis from the Dermis, and tissue fluid
may collect, causing a BLISTER.
• If the skin is subjected to pressure, the rate of mitosis will
increase and create a thicker Epidermis; we call this a
CALLUS.
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