Anatomy and Physiology Lecture: Eye Structure and Function

Introduction

• Instructor: Professor Bob Long
• Course: Human Anatomy and Physiology II at Del Mar College
• Focus: Sensory Physiology - specifically the eye (second video in series)
• Note: The material may be trimmed for relevance to allied health science programs

Overview of Eye Structure

• The eye is composed of three main layers known as tunics:
  1. Fibrous Tunic
  2. Vascular Tunic
  3. Neural Tunic

Fibrous Tunic

• Components:
  • Sclera:
    • Known as the white part of the eye
    • Composed of dense connective tissue (collagen fibers)
    • Functions:
      • Provides shape and support
      • Strong attachment point for extraocular muscles (4 major muscles: superior rectus, medial rectus, lateral rectus, inferior rectus)
  • Cornea:
    • Transparent part allowing light to enter the eye
    • Refracts light slightly, termed translucent

Vascular Tunic

• Components:
  • Choroid (Choroid Plexus):
    • Supplies oxygen, nutrients, and removes waste
  • Ciliary Body:
    • Composed of:
      • Ciliary Muscle: Controls lens shape for focusing
      • Suspensory Ligaments: Suspend the lens
      • Lens: Elastic, changes shape to focus light
  • Iris:
    • Pigmented, controls light entering the posterior cavity
    • Contains two muscles:
      • Pupillary Constrictor Muscle: Decreases pupil size in bright light or parasympathetic stimulation
      • Pupillary Dilator Muscle: Increases pupil size in low light or sympathetic stimulation

Extraocular Muscles

• Functions of Muscles:
  • Superior Rectus: Moves eye upward
  • Medial Rectus: Moves eye towards the midline
  • Lateral Rectus: Moves eye outward
  • Inferior Rectus: Moves eye downward
• Cranial Nerve Control:
  • Cranial Nerve 3 (Oculomotor): Controls most eye muscles
  • Cranial Nerve 4 (Trochlear): Controls superior oblique
  • Cranial Nerve 6 (Abducens): Controls lateral rectus

Important Concepts

• Pupil Adjustment:
  • Pupillary constriction and dilation regulate light entry to ensure optimal vision
• Choroid Function:
  • Plays a critical role in maintaining the health of neurons in the retina by providing a filtered blood supply

Key Takeaways

• Understanding of the eye's anatomy is essential for recognizing how visual processes work
• Each component of the eye has a specific role that aids in vision and focus