Anatomy

Cornea

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Cornea, Corneal Epithelium, Bowman's Membrane, Corneal Stroma, Corneal Endothelium, Descemet's Membrane

  • Definition
  1. Transparent front refractive window of eye
  • Anatomy
  1. eyeGlobeXsGrayBB869.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  2. eyeCorneaLensGrayBB883.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  • Physiology
  1. Dimensions
    1. Vertical: 11.6 mm
    2. Horizontal: 11.5 mm
    3. Thickness
      1. Peripheral: 1 mm
      2. Central: 0.55 mm
  2. Five distinct layers
    1. Epithelium (Exterior layer of Cornea, a few cells thick)
      1. Prevents infection
      2. Smooth refractive surface
      3. Produces the tear film
      4. Continually regenerates
    2. Bowman's Membrane
    3. Stroma (90% of Corneal thickness)
      1. Composed of collagen fibrils intertwined
      2. Supportive structure of Cornea
    4. Endothelium
      1. Dehydrates Cornea via Na-K ATP Pump
      2. Relative dehydration maintains Corneal clarity
    5. Descemet's Membrane (Interior Layer of Cornea)
      1. Endothelium basement membrane
  3. Function
    1. Barrier protection
    2. UV light filtration
    3. Refraction
      1. Cornea provides 65-75% of eye's focusing power
      2. Unlike lens, Cornea's Refraction power is fixed
  4. Blood supply
    1. No direct blood supply to maintain transparency
    2. All nutrition supplied indirectly
      1. Tears
      2. Ambient oxygen
      3. Aqueous Humor of anterior chamber