Anatomy of the Skin

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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

• Serving as a barrier against infection and
  disease
• Helping to regulate body temperature
• Removing waste products from the body
• Providing protection against Ultraviolet
  radiation from the sun
• Producing vitamin D

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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 deepest to most superficial
• Stratum basale
• Stratum spinosum
• Stratum granulosum
• Stratum lucidum
• Stratum corneum

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Dermis

• on average 1.0-2.0mm thick

• contains dermal papillae

• 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

• 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 Meisners 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
• varying amounts of melanin
• varying size of melanin granules
• albinos lack melanin

• Physiological Factors
• dilation of dermal blood vessels
• constriction of dermal blood vessels
• 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 -burn
s 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

• 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

• Skin becomes scaly
• Age spots appear
• Epidermis thins
• Dermis becomes reduced
• Loss of fat
• Wrinkling
• Sagging
• Sebaceous glands secrete less oil

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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.