Chapter 5 Integumentary System

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Chapter 5 Integumentary System

• The Structure of the Skin

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The Integumentary System

• Is made up of the skin and its accessory
  structures
• It functions to guard the bodys physical and
  biochemical integrity, maintain constant body
  temp and provide sensory info about the
  environment

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Skin

• Weighs 10-11 lbs in an adult
• Is classified as an organ
• Covers approx. 22 square feet (adult)
• Dermatology is the medical specialty that deals
  with diagnosing and treating skin disorders

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The Function of Skin

• Blood reservoir
• Excretion
• Immunity
• Body temp regulation
• Protection from Ultraviolet light

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Regions of the Skin

• Epidermis-
• Most superficial layer
• Made of epithelial tissue
• Dermis
• Made of connective tissue
• Hypodermis
• Not part of the skin
• Made of areolar and adipose tissues

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Epidermis

• Made of kerainized stratified squamous epithelium
• Contains 4 types of cells
• Keratinocytes
• Melanocytes
• Langerhans cells
• Merkel Cells

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Keratinocytes

• Produce the protein keratin, that helps to
  waterproof and protect the skin
• 90 of epidermal cells produce keratin

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Melanocytes

• Produce the pigment melanin
• Melanin produces skin color, increases in the
  amount of the pigment makes the skin darker
• Melanin plays a critical role in protecting the
  skin from UV light.
• Melanocytes make up about 8 of the cells of the
  epidermis

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Langerhans Cells

• Arise from Red bone marrow
• Provide the immune response against invading
  microbes.

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Merkel Cells

• Functions in the sensation of touch
• Contact a sensory structure called a tactile
  (Merkel) disc

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The 5 Layers of the Epidermis

• Stratum basale
• Stratum spinosum
• Stratum granulosum
• Statum licidum (found only in soles and palms)
• Stratum corneum

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Stratum basale

• The deepest layer of the epidermis
• Contains some stem cells
• Cell division occurs here

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Stratum spinosum

• Provides strength and flexibility to the skin

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Stratum granulosum

• 3-5 layers of cells
• Keratinization happens here
• The layer between the deeper, living cells and
  the dead- superficial cell layer

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Stratum lucidum

• Present only in fingers, soles of the feet and
  palms of the hand.
• Contains extra layers of dead keratinocytes for
  extra protection against friction.

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Stratum corneum

• The most superficial layer of cells
• Made up of DEAD cells
• Lamellar granules make this layer waterproof
• Constant exposure to friction will cause this
  layer to increase to form a callus

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Dermis

• Composed mainly of connective tissue
• Collagen and elastic fibers
• Blood vessels, nerves, glands and hair follicles
  are embedded here.
• Made of two layers

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Papillary Layer

• Dermal papillae- small finger-like projections
  that increase the surface area of this layer
• These papillae contain capillary loops and nerve
  endings sensitive to touch
• Free nerve endings here also give sensations of
  warmth, coolness, pain, tickling and itching

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Reticular Layer (Region)

• Collagen and fibers
• Results in elasticity and extensibility
• Epidermal ridges that provide the basis for
  fingerprints
• Important to increase friction
• Do not change thru life
• Sweat glands open on top of ridges (to leave
  fingerprints)

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Structural Basis of Skin Color

• 3 pigments-
• Melanin
• Carotene
• Hemoglobin
• Albinism- inherited inability of an individual to
  produce melanin.