Overview of Eyeball Structure and Function

Aug 26, 2024

Take quiz

Structure of the Eyeball Lecture Notes

Introduction

  • Overview of the structure of the eyeball.
  • Importance for understanding phototransduction, retina, and optic pathways.

Key Topics Covered

  1. Tunics of the Eye
  2. Segments: Anterior and Posterior
  3. Flow of Aqueous Humor and Lacrimal Flow
  4. Clinical Correlations

Tunics of the Eye

  • Fibrous Tunic

    • Components: Sclera and Cornea
    • Sclera
      • Three layers: Episclera, Scleral Proper, and Lamina Fusca
      • Dense fibrous connective tissue, rich in collagen.
      • Clinical correlation: Jaundice can cause discoloration.
    • Cornea
      • Five layers: Epithelial Layer, Bowman's Membrane, Stroma, Descemet's Membrane, Endothelial Layer
      • Rich in pain receptors; allows light transmission.
      • Lacks blood supply, minimizing transplant rejection.

  • Vascular Tunic (Uvea)

    • Components: Choroid, Iris, Ciliary Body
    • Choroid
      • Pigmented membrane; absorbs light to prevent scattering.
      • Rich vascular supply.
    • Iris
      • Muscles: Dilator Pupillae (Sympathetic) and Sphincter Pupillae (Parasympathetic)
      • Controls pupil size; determines eye color.
    • Ciliary Body
      • Ciliaris Muscle: Involved in accommodation reflex for vision.
      • Ciliary Processes: Secretes aqueous humor.

  • Sensory Tunic

    • Retina
      • Neural layer with photoreceptors, bipolar cells, ganglion cells.
      • Pigmented layer with melanin; prevents light scattering.
    • Vitreous Humor
      • Occupies the posterior segment; supports retina.
      • Transmits light rays and maintains intraocular pressure.
      • Produced during embryonic development.

Segments of the Eye

  • Anterior Segment

    • From cornea to lens.
    • Contains aqueous humor (flow from ciliary processes, through pupil, to anterior chamber, drains via canal of Schlemm).

  • Posterior Segment

    • From lens to retina.
    • Contains vitreous humor.

Lens

  • Made of crystallin proteins (lens fibers) and epithelial cells.
  • Responsible for light refraction.
  • Clinical correlation: Cataracts result from crystallin accumulation.

Additional Structures

  • Conjunctiva: Lines the eyelid and covers the sclera.
    • Palpebral and bulbar conjunctiva.
    • Clinical correlation: Conjunctivitis (pink eye).
  • Eyelids and Tarsal Plates
    • Provide attachment for muscles.
    • Contain tarsal glands for lubrication.

Lacrimal Flow

  • Flow of tears from lacrimal gland, across the eye, into nasal cavity.
  • Steps: Lacrimal gland secretion → Across cornea → Lacrimal puncta → Canaliculi → Lacrimal sac → Nasolacrimal duct → Nasal cavity.

Optic Nerve

  • Optic nerve (Cranial Nerve II) connects eye to brain.
  • Pierces sclera at optic disc.

Conclusion

  • Summary of the anatomy and function of different components of the eye.
  • Next steps: Detailed exploration of the retina and phototransduction process.

These notes provide a comprehensive overview of the structural components of the eye and their functions, useful for further study and understanding of the subject matter.