Skin Anatomy

Aka: Skin Anatomy, Epidermis, Dermis, Hypodermis, Intraepidermal, Stratum Corneum, Cornified Layer, Stratum Lucidum, Stratum Granulosum, Granular Layer, Stratum Sprinosum, Prickle Cell Layer, Stratum Germinativum, Stratum Basale, Basal Cell Layer, Keratinocyte, Desmosome, Macula adherens

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II. Anatomy

  1. Complete Cross Sectional Anatomy
    1. DermSkinAnatomy.jpg
    2. dermSkinXsFullThicknessGrayBB940.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  2. Epidermis
    1. dermEpidermisGrayBB941.gifLewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)

III. Definitions

  1. Epidermis (external skin surface)
    1. Keratinised squamous epithelium
    2. Thickness
      1. Eyelids: 0.05 mm
      2. Palms and soles: 1.5 mm
  2. Dermis (supports Epidermis)
    1. Thick, dense, fibroelastic connective tissue
    2. Highly vascularized
    3. Contains Sensory Receptors
  3. Hypodermis (Subcutaneous layer)
    1. Loose connective tissue with adipose tissue

IV. Physiology: Skin Functions

  1. Sensation (largest sensory organ in the body)
  2. Protection
    1. Prevents Dehydration
    2. Prevents infection
    3. Physical barrier to injury
    4. Protects against ultraviolet light injury (Melanin)
  3. Thermoregulation
    1. Insulation (hair and adipose tissue)
    2. Heat dissipation
      1. Sweat evaporation
      2. Increased Blood Flow
  4. Metabolic
    1. Energy storage of Triglycerides in adipose tissue
    2. Vitamin D synthesis

V. Anatomy: Epidermis Cell Layers (cells mature from inner to outer)

  1. Stratum Corneum (Cornified Layer)
    1. Outermost layer of Epidermis
    2. Composed mostly of keratin (fibrous Protein)
    3. Cells desquamated (27 days after production)
  2. Stratum Lucidum (present only in very thick skin)
  3. Stratum Granulosum (Granular Layer)
    1. Darker layer with intracellular granules
    2. Produces keratin
  4. Stratum Spinosum (Prickle Cell Layer)
    1. Composed of Keratinocytes
    2. Cells produced by basal layer and growing
    3. Keratin production starts
  5. Stratum Germinativum (Stratum Basale, Basal Cell Layer)
    1. Innermost layer of Epidermis
    2. Cells are produced here in the germinal layer
    3. Forms the prickle cells in the layer above

VI. Anatomy: Interspersed cells and units

  1. See Hair Follicle
  2. See Sweat Gland
  3. See Sebaceous Gland
  4. See Melanocyte
  5. Merkel's Cell
  6. Langerhans Cells (in Prickle Layer)
    1. Dendritic histiocytic cells
    2. Intercept Antigenic signal and pass to lymphoid cells
  7. Desmosome (Macula adherens)
    1. Intercellular bridge that attaches epidermal cells
    2. Small dense Plaque with protruding tonofilaments

VII. References

  1. Habif (1996) Clinical Dermatology, Mosby, p. 24
  2. Murphy in Cotran (1989) Robbins Pathology, p. 1277-8
  3. Wheater (1987) Functional Histology, p. 130-2

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