Eyeball Anatomy

Introduction

• Tutorial by Anatomy Zone and Teach Me Anatomy on the anatomy of the eyeball.

• Eyeball: bilateral and spherical organ responsible for vision, housed within the bony orbit (facial skeleton).

Structure of the Eyeball

• Division of the Eyeball: Anatomically divided into three layers:

  • Fibrous Layer

  • Vascular Layer

  • Inner Layer

Fibrous Layer

• Components: Sclera and Cornea.

  • Sclera:

    • Makes up approximately 85% of the fibrous layer.

    • Provides shape and support, and attaches extraocular muscles for eye movement.

    • Visible as the white part of the eye.

  • Cornea:

    • Transparent, anterior continuation of the sclera.

    • Refracts light entering the eye.

Vascular Layer

• Components: Choroid, Ciliary Body, Iris.

  • Choroid:

    • Layer of connective tissue and blood vessels.

    • Nourishes outer layers of the retina.

  • Ciliary Body:

    • Comprised of the ciliary muscle and ciliary processes.

    • Controls lens shape via zonular fibers (suspensory ligament of the lens).

    • Ciliary Muscle:

      • Smooth muscle fibers in three orientations (longitudinal, circular, radial).

      • Contraction reduces diameter, facilitates lens accommodation for near vision.

      • Relaxation increases diameter, flattening the lens for distance vision.

  • Iris:

    • Circular structure with a central pupil aperture.

    • Eye color determined by the iris.

    • Pupil Size Control:

      • Circular Fibers (sphincter pupillae): Innervated by parasympathetic system for constriction.

      • Radial Fibers (dilator pupillae): Innervated by sympathetic system for dilation.

Inner Layer

• Components: Retina (neural and pigmented layers).

  • Neural Layer:

    • Contains photoreceptors, located posteriorly and laterally.

  • Pigmented Layer:

    • Supports the neural layer, attached to the choroid.

    • Anterior continuation forms the non-visual retina.

• Optic Part of the Retina:

  • Viewed during ophthalmoscopy or fundoscopy.

  • Macula Lutea:

    • Yellowish area containing fovea centralis (high concentration of cones for color vision).

  • Optic Disc:

    • Entry point for the optic nerve, contains no light-detecting cells (blind spot).

Fluid Areas

• Chambers of the Eye:

  • Anterior Chamber: Between cornea and iris.

  • Posterior Chamber: Behind the iris, anterior to lens.

• Aqueous Humor:

  • Nourishes and protects the eye, secreted into the posterior chamber, flows to the anterior chamber, absorbed into canal of Schlemm (scleral venous sinus).

  • Obstruction can lead to glaucoma due to increased intraocular pressure.

Vitreous Chamber

• Vitreous Humor:

  • Gel-like substance filling the eyeball, extends from behind the lens to the retina.

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Conclusion

• Overview of the anatomy of the eyeball.

• Next tutorial will focus on vascular supply of the eyeball.

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