Integumentary System Skin_ Hair_ and Nails - ClassJump

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					Integumentary System:
 Skin, Hair, and Nails
         Ch. 5
 Functions of the Skin
1. Protection – the skin prevents the entry of microorganisms,
   acts as a permeability barrier, and provides protection
   against abrasion and UV light
2. Sensation – the skin contains sensory receptors for pain,
   heat, cold, and pressure
3. Vitamin D production – UV light stimulates the production
   of a precursor molecule in the skin that is modified by the
   liver and kidneys to make vitamin D
4. Temperature regulation – Through dilation and constriction
   of blood vessels, the skin controls heat loss; plus,
   evaporation of sweat cools the body
5. Excretion – Skin glands remove small amounts of waste
Skin - Structures and
 Accessory Organs
Skin Structure
   Skin composed of two kinds of tissue
       Outer EPIDERMIS=stratified squamous capable of keratinizing
        (becoming hard/tough)
       Underlying DERMIS=dense connective tissue
       Epidermis and dermis (which is 20x thicker) are firmly
            Burns cause separation = blister

   EPIDERMIS composed of 5 layers called STRATA

   DERMIS composed of 2 layers

   Deep to dermis is the SUBCUTANEOUS TISSUE
    (HYPODERMIS) which is essentially loose adipose tissue
       NOT considered part of the skin
       Serves as shock absorber and insulates deeper tissues
       Has lots of blood vessels
Skin Structure - Actual Picture
   1. Epidermis - 5 Strata

 P     Corneum
       Lucidum
 E     Granulosum
       Spinosum
 I     Basale
                    “Californian Ladies Give Superb Backrubs”
a. Stratum Corneum
   Found at surface of thick and thin skin
       Normally 15-20 layers of keratinized cells
   Keratinization ccurs in exposed skin surfaces
    except anterior surfaces of the eye
   Dead cells within each layer remain tightly
    interconnected by desmosomes
   Shed as large sheets rather than single cells
   Layer is water-resistant but not waterproof
   Journey from stratum basale to stratum corneum
    takes about 15-30 days
   Dead cells remain in stratum corneum for about 2
    weeks before being shed or washed away
b. Stratum Lucidum
   This layer occurs ONLY where skin is
    hairless and extra thick
       Palms of hands and soles of feet

   Cells in this layer are clear, flattened,
    densely packed, and filled with keratin

   Doomed because NOT able to get
    adequate nutrients and oxygen
c. Stratum Granulosum
   “Grainy” layer superficial to stratum

   3-5 layers of keratinocytes that have
    stopped dividing

   Become more flatter and produce copious
    amounts of keratin

   Cells die and dehydrate creating tightly
    interlocked layer of keratin fibers
    surrounded by KERATOHYALIN
d. Stratum Spinosum
   STRATUM SPINOSUM layer situated above
    stratum basale; means “spiny layer”

   Consists of 8 to 10 layers of cells, mostly
    KERATINOCYTES (most abundant
    epithelial cells) bound together by

   Begin to become flatter and increasingly
    full of keratin

   Cells in this layer continue to divide
e. Stratum Basale
   STRATUM BASALE is deepest layer of
    epidermis; also called s. germinativum

   Lies closest to the DERMIS
       Contains the ONLY epidermal cells that receive
        adequate nourishment (diffusion) of nutrients
        from dermis

   Cells in this layer constantly undergoing

   Millions of new cells produced DAILY
2. Dermis
   Dermis is strong, stretchy envelope that helps
    hold body together (result of collagen and elastic

   Incisions made parallel to collagen fibers
    (cleavage lines) will scar less; stretch marks result
    when the dermis is damaged from overstretching

   Dense connective tissue making up dermis
    consists of two major regions:
       PAPILLARY LAYER is upper dermal region

       RETICULAR LAYER is the lower dermal region
a. Papillary Layer
   Uneven with fingerlike projections from its
    superior surface called DERMAL PAPILLAE
    which indent epidermis above

   Many dermal papillae contain capillary
    loops which supply nutrients to epidermis

   Other dermal papillae house pain
    receptors (free nerve endings) and touch
    receptors (Meissner’s corpuscles)
   On palms of hand and soles of feet,
    papillae arranged in definite pattern that
    forms looped and whorled ridges on
    epidermal surface that increase friction
    and enhance gripping ability of fingers and

   Ridges of fingertips covered with sweat
    pores and leave identifying film of sweat
    called FINGERPRINTS on nearly everything
    they touch
Can you identify –
loops, whorls, and arches?
b. Reticular Layer
   RETICULAR LAYER of dermis is deepest skin layer

   Contains blood vessels, sweat and oil glands, and
    deep pressure receptors (Pacinian corpuscles)

   Many phagocytes found in reticular layer

   Both collagen and elastic fibers found with layer

       Collagen = toughness of dermis but also attracts and
        binds water

       Elastic = skin elasticity during youth
                                      Skin Color
   Melanin is the group of pigments responsible for
    skin, hair, and eye color; molecules are brown to
    black, and/or reddish – yellowish

   Melanin provides protection from UV light

   It is produced by special cells called MELANOCYTES
    that are found primarily in stratum basale

   Large amounts of melanin occur in some regions of
    the skin, such as freckles, moles, and darker skin
                                              Skin Color
   Melanin production is determined by:
       genetic factors (different races and albinism)
       exposure to light (increase in melanin = suntan)
       hormones (pregnancy hormones will darken the nipples
        and genitalia, face and chest, and midline of abdomen)

   Besides melanin, carotene and hemoglobin also
    contribute to skin color:
       Carotene, like from squash and carrots, can be deposited in
        stratum corneum; give skin a yellow-orange pigment color
       Hemoglobin, a red pigment in RBCs that binds oxygen, can
        give skin a reddish hue when blood flow increases;
        decrease in blood flow makes you pale
3. Accessory Organs
   Skin appendages are hair and hair
    follicles, small muscles, glands, and nails

   Each originate in the dermis and arises
    from epidermis to help maintain
    a. Hair
   HAIR is produced by a root follicle and is a flexible
    epithelial structure
        The follicle encloses the HAIR ROOT and HAIR BULB
         (base of the root) in the dermal layer; it is nourished by
         blood vessels
        The HAIR FOLLICLE is an extension of the epidermis (s.
         basale) and helps with tissue repair
        The HAIR SHAFT is part projecting from surface of skin
         or scalp

   The hair shaft has three layers (cuticle, medulla,
    and cortex)
    Hair Growth
   Hair is produced in cycles:
       Growth Phase – formed by the epithelial cells of the
        hair bulb; cells divide and undergo keratinization;
        hair grows longer – as new cells form at bulb, and
        dead cells are moved up with the hair shaft

       Resting Phase – growth stops and hair is held in the
        follicle; when growth starts again, the old hair falls

       Examples: eyelashes (30 days growth, 105 days
        rest); scalp hairs (3 years growth, 1-2 years rest)
                              Goose bumps
   Small bands of smooth muscle cells called
    ARRECTOR PILI connect each side of hair
    follicle to dermal tissue

   When these muscles contract (cold,
    frightened), hair is pulled upright and we
    call the dimpled skin “goose bumps”

   Furry animals use these tiny muscles to
    thicken the fur layer and trap insulating
    air; also to appear larger and ferocious
b. Glands
   Are all EXOCRINE
    glands that release
    their secretions to skin
    surface via DUCTS

   Are two groups of
    cutaneous glands:

       Sebaceous glands
       Sweat glands (merocrine
        and apocrine)
    Sebaceous Glands
   These “oil glands” are found all over body except
    on palms of hands and soles of feet

   Ducts usually open into hair follicles but some
    open onto skin surface

   SEBUM is lubricant that keeps skin soft and moist
    and prevents hair from becoming brittle

   Sebaceous glands become very active when male
    sex hormones produced in > amounts (in both
    sexes) during adolescence; acne is an infection of
    these oil glands
Sweat Glands: Merocrine glands
   MEROCRINE sweat glands most numerous and are
    found all over the body

   Typically sweat reaches skin via duct opening
    externally as funnel-shaped pore

   These glands play important part of body’s heat
    regulating equipment; as sweat evaporates,
    carries large amounts of body heat with it

   SWEAT is a clear secretion that is primarily water
    plus some salts; is usually acidic (pH 4-6) which
    inhibits bacterial growth
Sweat Glands: Apocrine Glands
   Apocrine glands largely confined to axillary and
    genital areas of body

   Usually > than eccrine glands and their ducts
    empty into hair follicles

   Secretions contain water and salts plus fatty
    acids and proteins; the secretion is “odorless” but
    bacterial growth may impart musky, unpleasant

   Begin to function at puberty as a result of
    hormones (androgens)
    c. Nails
NAIL is scale-like modification of epidermis similar to
  hoof/claw of other animals

   Nails have a NAIL BODY (visible, attached portion) and ROOT
    (embedded in the skin; extending from the NAIL MATRIX)

   The CUTICLE is stratum corneum that extends onto the nail

   Stratum basale of epidermis extends beneath nail as the NAIL
    BED; the nail matrix and bed give rise to new cells – nails
    grow continuously

   The LUNULA is white crescent over the thickened nail matrix
Skin – A Diagnostic Aid,
  Disorders, & Aging
                                    Color Changes
   CYANOSIS - occurs when hemoglobin is poorly
    oxygenated and blood/skin of Caucasians appear

   JAUNDICE (yellow cast) - name given abnormal
    yellow skin tone; usually signifies liver disorder
       Excess bile pigments, which are yellow, are absorbed
        into blood and deposited in blood and body tissues; the
        liver is not working properly as a result of damage or
        disease like hepatitis

   ERYTHEMA (redness) - name given reddened
    skin and may indicate embarrassment, fever,
    hypertension, inflammation, or allergy
                            Blood Flow Changes
   PALLOR (blanching) - certain types of emotional
    stress (fear, anger, & others) cause some people
    to become PALE
       Pale skin may also signify anemia, low blood pressure, or
        impaired blood flow to area

   Bruises/Black and blue marks-reveal sites where
    blood has escaped from circulation and clotted in
    tissue spaces; Such clotted masses called HEMATOMAS

   Bedsores (decubitus ulcers) develop in people who
    are bedridden or confined to a wheelchair; weight
    compresses tissue and reduces blood flow – leads
    to destruction of hypodermis and skin
                       Nutritional Changes
   Vitamin A deficiency – skin produces excess
    keratin and has a sandpaper texture

   Vitamin C deficiency – easily bruised skin

   Iron-deficiency anemia – nails lose their normal
    contour and become flat

   High levels of lead can be detected in a hair
                          Three Types of Burns
   BURN is tissue damage and cell death caused by
    intense heat, electricity, UV radiation, or certain

   Burns are classified according to their severity

   FIRST-DEGREE-only epidermis is damaged
       Area becomes red and swollen
       Temporary discomfort but “usually” NOT serious
       Heal in 2-3 days without any special attention
       Sunburn is “usually” a first-degree burn
   SECOND DEGREE-involve injury to
    epidermis and upper region of dermis
       Skin red/painful and BLISTERS appear
       Sufficient numbers of epithelial cells still
        present, regrowth (regeneration) of epithelium
        can occur
       Normally, no permanent scarring results IF
        infection prevented

First- and Second-degree burns referred to
   THIRD-DEGREE-destroy entire thickness of skin
    and are called FULL-THICKNESS BURNS
      Burned areas appear blanched (gray-white) or
      Nerve endings in area destroyed so burn area
       NOT painful
      NO regeneration is possible so skin grafting
       required to cover underlying exposed tissues

   Considered CRITICAL if over 25% of body has
    second-degree burns or if over 10% of body has
    third-degree burns OR if there are third-degree
    burns of face, hands, or feet
                                         Rule of Nines
   Burns result in two life-threatening problems
       Body loses supply of fluids containing proteins and
        electrolytes as they seep from burned surface
       This dehydration/loss of electrolytes can lead to shut down
        of kidneys and CIRCULATORY SHOCK (inadequate
        circulation of blood due to low blood volume)

   Volume of fluid loss can be estimated indirectly by
    determining how much of surface has been burned
    using the RULE OF NINES

   Method divides body into 11 areas each accounting
    for 9 percent of total body surface

   Additional area surrounding genitals (perineum) =
    1 percent
                     Types of Skin Cancers
   Skin cancer most common cancer in humans

   BASAL CELL CARCINOMA - least malignant and
    most common skin cancer
      Cells of stratum basale, altered so can no
       longer form keratin, no longer honor boundary
       between epidermis and dermis
      Proliferate & invade dermis and subcutaneous
      Occur most often on face as shiny, dome
       shaped nodules that later develop central ulcer
       with “pearly” beaded edge
      Slow-growing and seldom metastasizes before
      Cure rate is 99% (surgical removal)
   SQUAMOUS CELL CARCINOMA - arises from cells of
    stratum spinosum
      Lesion is scaly, reddened papule (small, rounded
       elevation) that gradually forms shallow ulcer with
       firm, raised border
      Appears on scalp, ears, dorsum of hands, lower
      Metastasizes rapidly to lymph nodes if not
      Believed to be “sun-induced” but recovery rate
       good if caught early (surgery/radiation)
   MALIGNANT MELANOMA - is cancer of melanocytes
     Accounts for 5% of skin cancers, rate is rising,
      and CAN be deadly
     Can begin anywhere there is pigment (some
      begin at pigmented mole)
     Usually appear as spreading brown/black patch
      that metastasizes rapidly to lymph nodes and
      blood vessels
     Survival rate is about 50%
     The ABCDE Rule for Melanomas
   A (asymmetry) - two sides of pigment spot or mole
    do NOT match

   B (border irregularity) - borders of lesion are not
    smooth but exhibit indentations

   C (color) - pigmented spot contains areas of
    different colors (blacks, browns, tans, and
    sometimes blue and reds)

   D (diameter) - spot is larger than 6 mm in
    diameter (size of pencil eraser)

   E (evolution) – change or growth of a mole
Aging and the Skin
   Skin is more easily damaged because the epidermis thins
    and collagen decreases
   Decrease is elastic fibers in dermis and loss of fat in
    hypodermis cause skin to sag and wrinkle
   Decreased activity of sweat glands and decrease in blood
    supply to dermis result in poor ability to regulate body
   Decreased activity of sebaceous glands cause skin to
    become drier
   Amount of melanocytes increases in some areas to cause
    age spots
   Amount of melanin in hair can decrease (gray hair is a
    mixture of faded hair and white hair – w/ no melanin)

                                                   Good times!