Eyeball Anatomy Quiz

Study Notes

Eyeball Anatomy

Visual organ with an antero-posterior diameter of approximately 24 mm.
Composed of three concentric coats: outer, middle, and inner.
Contains three primary transparent components: aqueous humor, lens, and vitreous body.

Coats of the Eyeball

Outer Coat (Fibrous or Protective):
- Made of fibrous tissue; serves a protective function.
- Comprises:
  - Transparent cornea (anterior 1/6)
  - Opaque sclera (posterior 5/6)
  - Transition zone known as limbus, located between cornea and sclera.
Middle Coat (Vascular or Nutritive):
- Vascular in structure; provides nourishment.
- Includes:
  - Iris (anterior)
  - Ciliary body (middle)
  - Choroid (posterior)
Inner Coat (Neural):
- Formed by the retina, which is neural and responsible for vision.
- Central area known as macula, containing the fovea centralis at its center.

Transparent Contents of the Eyeball

Aqueous Humor:
- Found in anterior and posterior chambers.
- Anterior chamber: located between cornea and iris.
- Posterior chamber: located between iris and lens.
- Both chambers communicate through the pupil.
Lens:
- Located between iris and vitreous; essential for refractive and accommodative functions.
Vitreous Body:
- Positioned between lens and retina, providing shape and structure to the eyeball.

Ocular Adnexa

Includes:
- Eyelids and eyebrows
- Conjunctiva
- Lacrimal apparatus
- Extraocular muscles

Orbit

Bony cavity housing the eyeball.
Features four-sided walls with the base positioned anteriorly and apex posteriorly.

Visual System

Comprised of the optic nerve and associated connections to the visual cortex.

Ocular Blood Supply

Internal carotid artery branches into the ophthalmic artery, which further divides into:
- Retinal artery
- Posterior ciliary arteries (nourish optic nerve and choroid)
- Muscular arteries (supply extraocular muscles and contribute to anterior ciliary arteries)
Long and short ciliary arteries form circulus iridis major, supplying iris, ciliary body, and peripheral choroid.

Ciliary Ganglion

Located at the apex of the orbit, lateral to the optic nerve, measures approximately 1 x 2 mm.
Has three roots:
- Sensory root from the nasociliary nerve.
- Parasympathetic root from the third cranial nerve via the inferior oblique branch.
- Sympathetic root from fibers around the internal carotid artery.
Branches into short ciliary nerves, conveying sensory, parasympathetic, and sympathetic fibers from the eyeball, iris, and ciliary body.

Nerve Supply of the Eye

Optic Nerve (2nd cranial nerve): Responsible for vision.
Oculomotor Nerve (3rd cranial nerve): Innervates several eye muscles (medial rectus, inferior rectus, superior rectus, inferior oblique, and levator palpebrae) and provides parasympathetic fibers via ciliary ganglion.
Trochlear Nerve (4th cranial nerve): Supplies superior oblique muscle.
Trigeminal Nerve (5th cranial nerve): Sensory innervation with two branches:
- Maxillary division for lower lid skin
- Ophthalmic nerve for upper lid skin, nasociliary nerve, and sensory root to ciliary ganglion.
Abducent Nerve (6th cranial nerve): Supplies lateral rectus muscle.
Facial Nerve (7th cranial nerve): Innervates orbicularis oculi muscle.
Sympathetic Fibers: Supply blood vessels, dilator pupillae, and tarsal muscles.

Description

Test your knowledge on the anatomy of the eyeball, including its various coats and transparent components. Learn about the protective outer coat, nourishing middle coat, and the neural inner coat essential for vision.