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					        Integumentary System


Chapter 5 – Vertebrate Anatomy
                     5 Components of the
                   Integumentary System

•   Skin
•   Sweat glands
•   Oil glands
•   Hair
•   Nails
                          Basics about skin…
• Every square centimeter of human skin contains
   –   70 cm of blood vessels
   –   100 sweat glands
   –   230 sensory receptors
   –   55 cm of nerves
   –   15 oil glands
• The surface area of the skin is about 2 square
  meters
• The skin weighs about 9 – 11 lbs.
• Though the term “integument” means “covering”,
  the skin is obviously much more than just this…
        Skin is our primary barrier
                         against…

• Infection
• Heat loss
• Water loss
       Two Main Regions of the Skin
• Epidermis
  – Made of epithelial tissue
  – Outermost layer; thin
  – NOT vascular; nutrients reach this layer via diffusion
• Dermis
  –   Underneath the dermis
  –   Makes up the bulk of the skin
  –   Lots of leathery connective tissue
  –   vascularized
      Two Main Regions of the Skin

• 3rd layer – subcutaneous or hypodermis
  – Not technically part of the skin
  – Composed mostly of adipose tissue (fat)
  – Protects
  – Anchors skin to muscle
  – Allows skin to slide freely over underlying
    structures
  – Shock absorber and insulator
                      Epidermis in Detail

• 4 different types of cells in epidermis
  –   Keratinocytes
  –   Melanocytes
  –   Merkel cells
  –   Langerhans’ cells
                                  Epidermis in Detail
• Keratinocytes
  – Produce keratin
     • Protein that gives epidermis it’s
       protective qualities
  – Life of a keratinocyte:
     • Arise in the deepest part of the
       epidermis
     • Pushed toward skin surface by
       production of new cells underneath
     • By the time they reach the surface
       they are dead and scale-like
     • Millions of keratinocytes rub off
       daily – totally new epidermis every
       25-45 days
                                      Epidermis in Detail
• Melanocytes
   – Produce the pigment known as
     melanin
   – Melanin molecules form a pigment
     “shield” that protects the nucleus from
     UV radiation
   – A tan is your body’s effort to prevent
     you from getting skin cancer
   – All races have the same number of
     melanocytes
       • Differences in skin color are due to
         activity of these cells and/or how fast
         melanin breaks down once produced
   – Click HERE for “I Am Joe’s
     Melanocyte”
                         Epidermis in Detail
• Langerhans’ cells
   – Help activate the
     immune system
   – Shown at right
• Merkel cells
   – Involved in forming
     sensory receptors that
     sense touch
             Layers of the Epidermis

• Thick skin of the palms, fingertips and soles
  of feet has 5 layers of epidermis
• Other skin has only 4 layers that are
  themselves thinner as well.
               Layers of the Epidermis
• Deepest Layer –
  Stratum Basale
  – Firmly attached to
    dermis underneath
  – Youngest keratinocytes
               Layers of the Epidermis
• Stratum spinosum
  – Next layer up from
    stratum basale
  – Cells appear spiney
                   Layers of the Epidermis
• Stratum granulosum
   – Cells flatten as they pass
     through this layer
   – Nuclei and organelles
     disintegrate
   – Cells accumulate
     waterproofing granules
   – The keratinocytes are
     “toughening up” in
     preparation of becoming the
     protective outer layer
                 Layers of the Epidermis
• Above stratum
  granulosum, cells die
   – They are too far away
     from dermal capillaries
     to receive adequate
     nourishment
               Layers of the Epidermis
• Stratum lucidum
  – Only present in thick
    skin
  – Thin translucent band
    above the stratum
    granulosum
                           Layers of the Epidermis
• Stratum corneum
   – 20-30 cell layers thick
   – Keratin and thick cell
     membranes of these cells
     protect the skin against
     abrasion and penetration
   – Glycolipids between the cells
     waterproof this layer
   – Cornified or “horny” cells are
     the cell remnants of the
     stratum corneum
       • These are familiar as
         dandruff
       • The average person loses 40
         lbs. of skin in a lifetime
                                       Dermis in Detail

• Strong flexible connective
  tissue layer
• Richly supplied with
   –   Nerve fibers
   –   Blood vessels
   –   Lymph vessels
   –   Major parts of hair follicles
   –   Major parts of oil glands
   –   Major parts of sweat glands
                      Layers of the Dermis
• Two layers:
  – Papillary layer
  – Reticular layer
                      Layers of the Dermis
• Papillary layer
   – Can lie atop dermal
     ridges
   – Creates epidermal
     ridges that aid in
     gripping – fingerprints
                         Layers of the Dermis
• Reticular layer
   – 80% of dermis
   – Lots of collagen fibers
      • Give strength and
        resiliency – prevents
        most jabs from entering
        dermis
   – Also elastin fibers
      • Provide stretch/recoil
             Clinical Aspects of Dermis
• Stretch marks
   – Silvery white scars
     caused by dermal tears
• Blisters
   – Epidermis and dermis
     become separated by a
     fluid filled pocket
                              Skin Color

• Only pigment MADE in the skin that
  contributes to skin color is melanin
• Melanocytes of dark-skinned people
  produce more and darker melanin that those
  of light-skinned people
• Local accumulations of melanin = freckles
  and pigmented moles
                                    Skin Color

• Melanocytes become more active upon
  exposure to sun
• Purpose of melanin is to protect DNA from
  UV radiation
  – Initial signal for speed up of melanin
    production is increased rate of repair of photo-
    damaged DNA!
                                   Skin Color

• 3 effects of excessive sun exposure
  – Clumping of elastin fibers – leathery skin
  – Depression of immune system
  – Alter DNA >> Cancer
                                     Skin Color

• Some chemicals can make people especially
  sensitive to light – photosensitivity
  –   Antibiotics
  –   Antihistamines
  –   Perfumes
  –   Detergents
  –   May cause itchy, blistery lesions; then peeling
      in sheets
                                        Skin Color

• Other pigments that color the skin (but are
  not MADE in the skin)
  – Carotene
     • Yellow/orange
     • Accumulates in stratum corneum
  – Hemoglobin
     • Pigment in blood
                              Skin Color
• Jaundice
  – Excess bile pigments
    (bilirubin) accumulate
    in the blood and
    deposit in body tissues
  – Yellow
                               Skin Color
• Bruises
  – Black and blue marks
    indicate blood escaped
    from circulation and
    clotted beneath the skin
  – Hematoma
               Appendages of the Skin

•   Hair follicles
•   Hair
•   Nails
•   Sweat glands
•   Sebaceous glands
                          Sweat Glands

• Found almost everywhere on the skin
• 2.5 million sweat glands on a person
• There are two types of sweat glands
  – Eccrine
  – Apocrine
                     Sweat Glands - Eccrine
• Most abundant on palms, soles of feet and
  forehead
• The pore of the gland is on the skin’s surface
• Composition of Sweat
   –   pH of sweat – ranges from 4 to 6
   –   99% water
   –   Some salts
   –   Vitamin C
   –   Antibodies
   –   Traces of metabolic wastes
        • Urea, uric acid, ammonia
        • Lactic acid – attracts mosquitoes
               Sweat Glands - Eccrine
• Major role of sweat –
  assist in
  thermoregulation –
  control of body
  temperature
• Heat induced sweating
  begins on the forehead
• “Cold sweat” begins
  on the palms, soles of
  feet, armpits
                 Sweat Glands - Apocrine
• Location
   – Axillary (armpit) and genital areas
• Empty into hair follicles
• Begin to function at puberty
• NO role in thermoregulation
   – Seen as analogous to sexual scent glands in other animals
• Composition of apocrine sweat
   – True sweat PLUS fatty substances and proteins – a viscous
     and milky substance
   – Secretion of apocrine glands is initially odorless
      • It is the breakdown of the organic compounds by bacteria that
        causes odor
Sweat Glands - Apocrine
  Other Glands – highly modified
                    sweat glands

• Ceruminous glands
  – Lining of the external ear canal
  – Secrete wax
  – Deters insects and blocks entry of foreign
    material
• Mammary glands
  – Specialized glands that secrete milk in
    mammals
                            Sebaceous Glands
• Found everywhere on
  the skin EXCEPT
  palms and soles of feet
• Largest on the face,
  neck and upper chest
• Secrete sebum
• Glands become active
  at puberty
       Clinical Aspects of Sebaceous
                              Glands
• If a sebaceous gland
  becomes blocked we
  observe a “whitehead”
• If the material in the white
  head becomes oxidized, it
  darkens and results in a
  “blackhead”
• The inflammation of
  sebaceous glands
  accompanied by pimples
  is known as acne
   – Usually caused by a
     bacterial infection
                       Sebaceous Glands

• Function of Sebum
  – Softens and lubricates hair and skin
  – Slows water loss
  – Kills bacteria
• Sebum is usually secreted into a hair follicle
                  Hair and Hair Follicles
• Function of hair in MOST mammals is to keep
  warm
• The main function of OUR hair is to sense insects
  on the skin
• Hair on the scalp protects against
   – Heat loss
   – Physical trauma
   – sunlight
• Other hair
   – Eyelashes shield eyes
   – Nose hairs filter large particles from inhaled air
                                   Structure of Hair
• Hair is made of keratinized cells
• Shaft – part of the hair that projects from the skin
   – Outermost layer – cuticle
      • When cuticle wears away, “split ends” result – the inner
        keratin fibers fray
   – Hair type – determined by shape of shaft
      • Flat and ribbon like shaft results in curly/kinky hair
      • Round shaft results in straight hair
• Root – part of the hair that is embedded in the skin
• When melanocytes at the base of hair follicles
  decrease their production of melanin, gray/white
  hair results
Hair Shaft
             Structure of the Hair Follicle
• Deep end of the follicle
  is expanded and forms
  the hair bulb
• Root hair plexus
   – Sensory nerve endings
     wrapped around the hair
     bulb
   – Allow hairs to act as
     touch receptors
• Papilla
   – Carries capillaries (and
     thus nutrients) to the
     hair bulb
              Structure of the Hair Follicle
• Arrector pili
   – Tiny muscles
   – When they contract
     they pull the hair
     upright
   – Results in “goose
     bumps”
   – Used in other
     mammals for heat
     retention
       • “fluffing” of fur
         traps air and air is a
         good insulator
       • Virtually useless in
         humans
  Distrubution, Types and Growth
                          of Hair
• 100,000 hairs on an average scalp
• 30,000 in an average beard
• Male sex hormones called androgens (testosterone
  in particular) stimulates hair growth in both sexes
• Average rate of hair growth per week is 2mm
• About 90 hairs lost per day
• Eyebrows are shorter because life of hair follicle is
  less
        Distrubution, Types and Growth
                                of Hair
• Hair thinning and baldness
   – Rate of hair growth declines
     in 40s
   – Atrophy of hair follicles
       • Hairs are not replaced as
         fast as they are shed
   – Male pattern baldness
       • Genetically determined
       • Gene switches on that
         changes the way hair
         follicles responds to
         testosterone
                                         Nails

•   Scale-like modifications of the epidermis
•   Protect ends of fingers or toes
•   Correspond to hoofs and claws
•   Useful as tools
•   Lots of keratin
                                  Nails
• Nail bed – under the
  nail
   – Nail matrix
      • Responsible for growth
      • Visible as the “lunula”
   Functions of the Integumentary
                           System
• Protection
   – Provides 3 barriers
      • Chemical barrier
          – Low pH – inhibits bacterial growth
          – Bactericidal substances in sebum – inhibits bact. growth
          – Melanin protects against UV light
      • Physical barrier
          – Helps prevent foreign objects from penetrating skin
          – Waterproofed so that water and solutes may neither entor nor
            LEAVE the body
      • Biological barrier
          – Cells like Langerhans’ cells are active, living elements of the
            immune system
   Functions of the Integumentary
                           System
• Body Temperature Regulation
  – Sweat glands constantly secrete small amounts of sweat
  – Rise in body temp causes dermal blood vessels to
    dilate; sweat glands are stimulated
  – Up to 12 liters of water can be lost in one day
  – Cold external environment causes dermal blood vessels
    to constrict
     • Causes the warm blood to bypass the skin and the cold
       environment temporarily
   Functions of the Integumentary
                           System
• Cutaneous Sensation – many different types of
  sensory receptors sense different types of touch
   – Meissner’s corpuscles – sense carress, feel of clothing
   – Pacinian receptors – sense bumps, deep pressure
   – Root hair plexus – senses wind blowing hair; tug on
     hair
   – Bare nerve endings - pain
   Functions of the Integumentary
                           System

• Metabolic functions
  – Vitamin D is made only when sunlight strikes
    the skin
   Functions of the Integumentary
                           System

• Blood reservoir
  – Skin holds 5% of the body’s blood supply
  – Blood can be shunted from the skin to other
    organs (ex. Working muscles, stomach, etc.) as
    needed
  – Why you may feel cold after eating
   Functions of the Integumentary
                           System

• Excretion
  – Water, salt and nitrogenous wastes are all
    excreted through the skin in some amount…
   Homeostatic Imbalances of the
                           Skin

• Over 1000 different skin conditions exist
• Most are caused by
  – Bacterial infection
  – Viral infection
  – Yeast infection
   Homeostatic Imbalances of the
                           Skin

• Burns
  – More than 2 million Americans are treated for
    burns each year.
  – 12,000 die
  – Most immediate threat to life in severe burns
     • Catastrophic loss of body fluids
                                Skin Cancer
• Most tumors that arise on
  the skin are benign and do
  not metastasize
   – They do not spread
   – Example – a wart; caused
     by a virus
• Some skin tumors are
  malignant
   – Cancerous
   – Invade other body areas
                            Skin Cancer

• Important risk factor in nonmelanoma skin
  cancer is over exposure to sunlight (UV
  radiation)
• UV radiation appears to damage a tumor
  suppressor gene, thus allowing a tumor to
  begin and grow
                 Basal Cell Carcinoma
• Least malignant skin
  cancer
• Most common skin
  cancer
• Slow growing
• Full cure in 99% of
  cases
   – Excision
             Squamous Cell Carcinoma
• Appears as a scaly red
  bump
• Often found on scalp, ears,
  hands, lower lip
• Grows rapidly if not
  removed – metastasizes to
  lymph nodes
• Cure rate is good if caught
  early and removed
   – Surgery and radiation
                         Malignant Melanoma
• Most dangerous skin cancer
• Melanocytes become cancerous
• 5% of skin cancers are of this
  type
• About 1/3 appear from
  pigmented moles
• First appears as a spreading
  black/brown patch.
  Metastasizes rapidly to
  surrounding lymph and blood
  vessels
• Survival rate is 50%
          ABCDE Rule for Recognizing
               Malignant Melanoma
• A – Assymetry
• B – Border irregularity
• C – Color
• D – Diameter Larger
  than 6mm
• E - Elevation
                Related Clinical Terms
• Albinism
  – Inherited
  – Melanocytes do not
    make melanin
  – Skin is pink
  – Hair is pale/white
                  Related Clinical Terms
• Boil
  – Inflammation of hair
    follicles and sebaceous
    glands
  – Infection spread to
    dermis
  – Area of inflammed
    tissue gradually forms
    a pus-filled swelling
    that is painful to touch
                 Related Clinical Terms
• Callus
  – Gross thickening of the
    epidermis caused by
    persistent friction
                 Related Clinical Terms
• Cold Sore
  – Caused by herpes
    simplex infection
  – Virus localizes in a
    cutataneous nerve
  – Remains dormant until
    activated by some
    stressor like emotional
    upset, fever or UV
    radiation
                 Related Clinical Terms
• Contact dermatitis
   – Itching
   – Redness
   – Caused by exposure of
     skin to chemicals
                Related Clinical Terms
• Decubitus
  – Bedsores
  – Caused by continuous
    pressure
                 Related Clinical Terms
• Port Wine Stain
  – Most noticeable of
    birth marks
  – Deep red blotches
    resulting from an
    abnormally dense
    network of blood
    vessels beneath the
    skin surface
                  Related Clinical Terms
• Psoriasis
   – Chronic
   – Reddened epidermal
     lesions covered with
     dry silvery scales
   – May be disfiguring
   – Cause unknown
      • Autoimmune attack
        suspected
                  Related Clinical Terms
• Ringworm
  – Highly contagious
    fungal infection
  – May or may not be
    ring-shaped
  – Fungi feed on dead
    skin and wastes in
    sweat
  – Athletes foot is one
                            Related Clinical Terms
• Rosacea
   – Redness of face accompanied by
     rash-like lesions
   – Due to vasodilation of facial blood
     vessels
   – Sudden facial flushing that rapidly
     disappears, though each episode
     lasts longer
   – Can be brought on by exercise, hot
     fluids, alcohol
   – Can lead to mats of swollen veins
     and pustule clusters if untreated
   – Cause unknown – bacterial
     infection suspected
                   Related Clinical Terms
• Vitiligo
   – Most common skin pigment
     disorder
   – Loss of melanocytes
   – Uneven dispersal of
     melanin
   – Unpigmented skin regions
     surrounded by pigmented
     areas
   – Autoimmune cause
     suspected
                              More on Burns
• Degrees of Burns
  – 1st degree burn
     • Only produce redness
     • Least severe
                         More on Burns
• 2nd degree burn
   – Produce blisters
   – Moderately severe
                                        More on Burns
• Degrees of Burns
  – 3rd degree burn
     • Most severe
     • Tissue destroyed down to the
       level of muscle and/or bone
     • Requires skin grafts to repair
     • Greatest Dangers…
         – Initially
              • Loss of body fluids
              • May lead to shock and
                 organ failure
         – Later
              • infection
Degrees of Burns

				
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