Lecture Notes on Eye Anatomy and Accessory Structures

Learning Objective 1

• Objective: Identify and provide functions for the eye and accessory eye structures.
• Distinction between accessory eye structure and structures of the eye:
  • Accessory Eye Structure: Not part of the eye itself but in the eye region; plays a role in eye function.
  • Structure of the Eye: Contained within the eye or eyeball.

Accessory Eye Structures

1. Eyelids (Pelpa)

   • Location: Above and below the eye.
   • Functions:
     • Shade eyes during sleep.
     • Protect from excessive light and foreign objects.
     • Spread lubricating secretions over eyeballs.

2. Eyelashes and Eyebrows

   • Eyelashes: Extend from the border of each eyelid.
   • Eyebrows: Arch above the upper eyelid.
   • Functions:
     • Protect from foreign objects, sweat, and sun rays.
     • Initiate blinking when touched.

3. Lacrimal Caruncle (Lacrimal Apparatus)

   • Location: Inner eye, pink mound of tissue.
   • Functions:
     • Contains sebaceous (oil) and sweat glands.
     • Covers and protects tear ducts (lacrimal glands).

4. Conjunctiva

   • Description: Thin protective mucus membrane.
   • Types:
     • Palpebral Conjunctiva: Lines the inner eyelid.
     • Bulbar Conjunctiva: Covers the sclera.
   • Functions:
     • Keeps the eye and inner eyelids moist and lubricated.
     • Protects against dust, debris, and infection.

Structures of the Eye

Layers of the Eyeball

1. Fibrous Tunic

   • Components:
     • Cornea: Transparent, lets light into the eye.
     • Sclera: White part, provides protection and muscle anchor.
     • Canal of Schlemm: Drains aqueous humor from anterior chamber.

2. Vascular Tunic

   • Components:
     • Choroid: Brownish-red layer, supplies retina and sclera.
     • Ciliary Body: Contains ciliary muscles and processes.
     • Iris: Colored part, adjusts pupil size to control light entry.

3. Retina (Inner Tunic)

   • Contains photo receptors (rods and cones), macula lutea, fovea centralis, and optic disc.
   • Macula Lutea: High visual acuity spot.
   • Fovea Centralis: Only cones, highest visual acuity.
   • Optic Disc: Blind spot where optic nerve exits.

Additional Structures

• Anterior Cavity: Contains anterior and posterior chambers filled with aqueous humor.
• Posterior Cavity (Vitreous Chamber): Filled with vitreous humor, supports eye shape and retina placement.
• Lens: Focuses light onto the retina.

Recap of Eye Structures

• Cornea: Clear front part, light entry.
• Sclera: White part, protection and muscle anchor.
• Choroid: Supplies retina, has capillary network.
• Ciliary Body: Muscle and processes holding the lens.
• Iris: Controls pupil size, contains pigment.
• Macula Lutea & Fovea Centralis: High visual acuity areas in the retina.
• Optic Disc: Blind spot, optic nerve exit.
• Anterior & Posterior Cavities: Contains humor for nourishment and shape maintenance.
• Lens: Light focus on retina.