Fibrous Coat quiz

• Sclera


  • Dense, fibrous, collagenous structure
  • Occupies 5/6 of the eyeball
  • Contains openings and canals for vessels and nerves
• Cornea


  1. The clear, transparent front part of the eye

  2. Contains five distinguishable layers: Anterior epithelium, Bowman’s membrane, Corneal stroma, Descemet’s membrane, Endothelium
• Fibrous Coat


  • Made of dense connective tissue
  • Also known as Fibrous tunic, Sclero-corneal coat
  • Protects the eyeball from trauma
  • Maintains its shape
• Scleral opening


  • Anterior scleral foramina located at limbus, Perforated by Long Anterior Ciliary Arteries (AC)
  • Posterior Scleral foramina located at the entrance of the optic nerve, Pierced by CN#2 (Optic Nerve), Central Retinal Artery (CRA), Long and short Posterior Ciliary Artery (PCA), Posterior Ciliary Nerves
• Tear film functions


  • Polishes the corneal surface
  • Mechanically traps foreign bodies
  • Flushes out foreign bodies chemicals
  • Contains bacteriostatic substances to inhibit the growth of microorganisms
  • Reduces surface friction associated with eyelid blinking and eye movement
• Tear film is made up of three layers: Oil (lipid) layer, Water (aqueous) layer, Mucin layer
• Components of the Fibrous Coat


  • Sclera: forms 5/6th of the outer coat
  • Cornea: forms 1/6th of the outer coat
  • Sclero corneal junction or Limbus
• Structure of the eyeball

  1. Fibrous coat or Sclero - corneal coat (outermost layer)

  2. Uvea or Vascular coat (Middle layer)

  3. Nervous Coat or functional coat (innermost layer)
• Sclera


  • Externally colored white
  • Internally slightly brown due to pigmented melanocytes
  • Avascular
  • Composed of collagen and fibrocytes
  • Covered by Tenons capsule and Bulbar conjunctiva (exposed portion)
• Cornea


  • Refracts light rays
  • Enables light to pass through the retina
  • Avascular except at limbal area
  • Factors that make cornea transparent: avascular, no pigment, regularly arranged fibers, non-keratinized corneal epithelium, collagen fibers at equal distance, small collagen fibers, tight junction of epithelial cells, dynamic balance between ions and water in corneal stroma
• Sources of Tear film


  • Lacrimal gland
  • Accessory lacrimal glands
  • Meibomian glands
  • Goblet cell
• Sclera helps contain the intraocular pressure
• Limbus or Sclero-corneal junction is the transition zone of the cornea and the sclera, containing Trabecular meshwork and Schlemm canal, serving as pathways of aqueous humour outflow and sites of surgical incisions for cataract and glaucoma