Special Receptor Organs

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Special Receptor Organs
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The Eye

• Eye - three layers
• a) tunica fibrosa, external layer
• (sclera, cornea)
• b) tunica vasculosa, middle layer (uvea)
• c) tunica interna, inner layer (retina)

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The Eye

• Tunica fibrosa - outer layer
• 1) sclera (opaque, posterior 5/6)
• 2) cornea (transparent, anterior 1/6)
• Sclera - three layers
• a) episclera - outer fibro-elastic layer
  continuous with Tenon's Capsule of the orbit.
  Covered by conjunctiva on anterior globe up to
  the cornea
• b) sclera proper - middle DICT layer
• c) Suprachoroidal lamina (lamina fusca) - inner
  pigmented areolar CT layer.
• Few blood vessels in the sclera.

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Cornea

• Transparent, 0.5mm thick with a smooth
  epithelial surface. Highly refractive
• Cornea - five layers
• outer non-cornified stratified squamous
  epithelium.
• - microvilli, microplicae, tear film (7 mm thick)
• b) Bowman's Membrane - microfibrillar outer
  layer of substantia propria, cell free.
• c) Substantia Propria (Stroma) - layered DRW,
  fibroblasts, major part of cornea.
• d) Decemet's Membrane - amorphous matrix lamina
  from the epithelium.
• e) inner epithelial layer of simple squamous
  epithelium (corneal endothelium).

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Cornea

• Limbus Corneoscleral junction. transition zone
  between substantia propria and episclera/sclera
  proper where white fibers fold over and
• 1) form a ridge (scleral spur)
• 2) produce a tube Canal of Schlemm, drained
  by Choroid veins
• 3) produce loose tissue packing, tissue spaces
  Trabecular meshwork.
• If the Canal of Schlemm or TM become occluded,
  cycling of aqueous humor is stopped causing fluid
  build-up increased intraocular pressure
  Closed Angle Glaucoma.

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Uvea

• B. Tunica Vasculosa (Uvea) - vascular,
  nutrient, middle layer.
• Composed of three regions
• a) choroid
• b) ciliary body
• c) iris

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Uvea

• Choroid - forms most of the uvea pigmented
  areolar CT with many vessels.
• Smooth muscle cells present innermost layer
  forms a thin hyaline membrane (Bruchs Membrane)
  for the pigmented epithelium layer of the retina.
• Extends forward to the Ora Serrata.

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Uvea

• Ciliary Body anterior expansion of choroid at
  the level of the lens. Smooth muscle (ciliary
  muscle) body of three layers with finger-like
  processes extending into the vitreal chamber
• - firmly attached to the scleral spur by areolar
  CT
• Ciliary Processes covered with ciliary
  epithelium, pars ciliaris retina (secretes
  aqueous humor into posterior chamber)
• - Attach to the lens by oxytalan fibers, Zonula
  or Zonule Fibers, secreted by non-pig. CE.
  Functions in accommodation.

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Uvea

• Iris - most anterior part of the uvea plate of
  thin areolar CT with many melanocytes
• Anterior surface covered by simple squamous
  epithelium.
• Inner rim forms the pupil a ring of
  myoepithelium (sphincter pupillae muscle
  surrounds the pupil and controls its diameter
  (parasympathetic)
• Dilator Pupillae Muscle (Sympathetic)
• Pars Iridica Retina
• Number and distribution of pigment cells
  responsible for eye color.

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Iris Biometrics ! Unique Identifier
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Lens

• Biconvex elastic structure
• Three Components
• Lens Capsule, Type IV Collagen Basement Membrane
• Subcapsular Epithelium, anterior surface, simple
  cuboidal epith.
• Lens Fibers- cells, from subcapsular epith.
  Loose their nucleus and organelles, fill with
  crystallins

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Retina

• Tunica Interna (nervosa retina) - nervous
  component and sensory receptor for light.
• Three regions
• pars optica retina
• - Cuboidal pigment epithelium, neural components
• b) pars ciliaris retina
• c) pars iridica retina

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Pars Optica Retina

• Ten Layers
• a) outer pigmented epithelium
• b) rod and cone layer (more rods than cones)
• c) external limiting membrane (Cells of Muller)
• d) outer nuclear layer
• e) outer plexiform (synaptic) layer
• f) inner nuclear layer
• g) inner plexiform layer
• h) ganglion cell layer
• i) optic nerve fiber layer (vascularized)
• j) internal limiting membrane (Cells of Muller)

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