The Integumentary System

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The Integumentary System

• Chapter 5

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The Integumentary System

• Composed of the skin, sweat and oil glands, hair,
  and nails.
• Accounts for 7 of the bodys weight.
• Major role is protection from pathogens and
  dehydration.
• Varies in thickness from 1.5 to 4.0 mm.
• Composed of 3 distinct layers.
• Epidermis, Dermis, and hypodermis or superficial
  fascia

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Epidermis

• Outermost layer.
• Composed mostly of keratinized stratified
  squamous epithelium.
• Contains 4 distinct cell types and 4 to 5
  distinct layers.

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Cell Types of the Epidermis

• Keratinocytesproduce keratin, a fibrous protein
  that give the epidermis its protective
  properties. These cells are tightly connected by
  desmosomes. Arise from the stratum basale.
  Undergo continuous mitosis. Are pushed upward
  and continuously become more keratinized.Those on
  the surface of the skin are dead. Millions rub
  off per day.
• Friction may lead to a thickening of the cells
  known as a callus.

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Cell Types of the Epidermis

• Melanocytessynthesize melanin.
• Located at the deepest layer of the epidermis.
• The melanin is transferred to the keratocytes.
• Protects against UV damage.

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Cell Types of the Epidermis

• Langerhans cellsarise from the bone marrow.
• Act as macrophages that activate the immune
  system.
• Merkel cellspresent at the junction of the
  epidermis and dermis. Associated with sensory
  receptors.

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Layers of the Epidermis

• Thick skin (on palms, fingertips, soles) has 5
  strata.
• Thin skin has only 4. The stratum lucidum is
  absent and the other layers are visibly thinner.
• Stratum Basaledeepest layer. Attached to the
  dermis. Sometimes called the stratum
  germinativum because of the constant mitosis that
  occurs there. Made of a single row of
  keratinocytes.

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Layers of the Epidermis

• Stratum SpinosumSeveral layers thick. Contain
  many intermediate filaments. Consist mainly of
  keratin like filaments. Resist tension. Melanin
  granules and Langerhans cells are abundant in
  this layer.
• Stratum Granulosum3-5 cell layers
  thick.Keratinocytes become more flattened and the
  cells contain more keratin and lamellated
  granules.
• Stratum Lucidumthin layer of dead keratinocytes.
  Present only in thick skin.

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Layers of the Epidermis

• Stratum CorneumOutermost layer. 20-30 cell
  layers thick. Cells have thick cell membranes
  and a great deal of keratin.Cells are referred to
  as cornified.

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The Dermis

• Made mostly of connective tissue.
• The hide of the human body.
• Richly innervated and vascularized.
• Contains the hair follicles, sweat glands, oil
  glands, lymphatic vessels, and many sensory
  receptors.

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The Dermis

• Consists of 2 layers.
• Papillary layerareolar connective tissue,
  heavily vascularized. Contains the dermal
  papillae, capillary loops, and Meissners
  corpuscles.
• In some areas these lie on top of the dermal
  ridges. Cause the epidermal ridges that cause
  fingerprints.
• Reticular layerdense irregular connective
  tissue.
• Importance of this structure.
• Flexure lines.

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The Dermis

• Skin colordetermined by melanin, carotene, and
  hemoglobin.
• Why do different people have different skin
  colors?
• Freckles moles
• Role of melanin
• Role and source of carotenes hemoglobins.

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The Dermis

• Photosensitivity
• Cyanosis
• Erythema
• Pallorpaleness
• Jaundice
• Bronzing
• Bruises hematomas

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Skin Appendages

• Sweat Glandsmore than 2.5 million per person.
• Eccrine sweat glandscoil in the dermis, a duct
  leads to a pore at the skins superficial
  surface.
• Sweat contents
• How does sweat work?
• Apocrine sweat glandsin the axillary and
  anogenital areas. Empty into hair follicles.
  Contains fatty substances and proteins. May
  cause body odor. Begin to function at puberty.
  May contain pheromones.

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Sin Appendages

• Ceruminous glandssecrete earwax.
• Mammary glandssecrete milk.
• Sebaceous Glandsoil glands. Found everywhere
  except the palms and soles.
• Secrete sebum.Usually secreted into hair
  follicles.
• Bactericidal other functions.

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Skin Appendages

• Whiteheads
• Blackheads
• Acnestaphylococcus
• Haircovers the entire body except for the palms,
  soles, lips, nipples, and parts of the genitalia.
• Functions of hair.
• Mostly dead keratinized cells.

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Hair

• Parts of the hair
• Shaft
• Medulla
• Cortex
• Cuticle
• Split ends
• Root
• Hair color
• Hair follicle
• Hair bulb
• Root hair plexus
• Arrector piliHow and why is this important?
• Hair papilla

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Hair

• Vellus Hairs
• Terminal Hairsandrogen sensitive
• Electrolysis
• Hirsutism
• Alopecia
• Male-pattern baldness
• Sex-influenced trait

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Nails

• Modification of the epidermis
• Composed of keratin.
• Composed of a free edge, body, and a root.
• Nail bedepidermis under the nail.
• Nail matrixgrowth occurs here.
• Lunula
• cuticle

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Functions of the Integument

• Chemical barriersacid mantle, human defensin
• Biological BarriersLangerhans cells and
  macrophages.
• Physical barrier
• Some substances can cross the skin.
• Lipid soluble substances.
• Oleoresinspoison ivy.
• Organic solvents.
• Salts of heavy metals

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Functions of the Integument

• Temperature Regulation
• Sweat glands
• Vasodilation and vasoconstriction
• Cutaneous Sensation
• Meissners corpuscles
• Pacinian corpuscles
• Root hair plexuses
• Pain and heat/cold receptors
• Metabolic Functions
• Vitamin D synthesis
• Blood Reservoir
• Shunts more blood into the circulation when
  needed.
• Excretion

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Skin disorders

• Causes
• Basal cell carcinoma30 of caucasians get this
  type of skin cancer. Does not metastasize.
• Squamous Cell carcinomaarises from the
  keratinocytes in the stratum spinosum. May
  metastasize.
• Melanomaarises in the melanocytes. Rapidly
  metastasizes.
• ABCD rule Asymmetry, Border irregularity, Color,
  Diameter

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Burns

• Denaturation of cell proteins.
• Dehydration, protein loss, and infection.
• First degree burnsonly the epidermis.
• Second degree burnsepidermis and upper dermis.
  May include blisters.
• Third degree burnsfull thickness. Not painful.
  Skin grafting is almost always necessary.
• Grafting techniques
• Autograft
• Dangers of facial burns and burns near joints.

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Aging Effects

• Lanugo Coat
• Vernix Caseosa
• Thinning of the skin
• Slowing of epidermal cell replacment.