QS Study

The eye is the organ of sight. An eyeball is a bilateral and spherical organ, which houses the structures responsible for vision.

The extraocular muscles are located within the orbit but are extrinsic and separate from the eyeball itself. They act to control the movements of the eyeball and the superior eyelid. The extraocular muscles of the eyeball are –

  • Superior rectus – Originates from the superior part of the common tendinous ring.
  • Inferior rectus – Originates from the inferior part of the common tendinous ring.
  • Medial rectus – Originates from the medial part of the common tendinous ring.
  • Lateral rectus – Originates from the lateral part of the common tendinous ring

Oblique Muscles are the superior and inferior obliques. Unlike the recti group of muscles, they do not originate from the common tendinous ring.

  • Superior oblique – Originates from the body of the sphenoid bone.
  • Inferior oblique – Originates from the anterior aspect of the orbital floor.

The intrinsic muscles of the eyeball are –

  • Sphincter papillae of iris
  • Dilator papillae of iris
  • Ciliary muscle.

Extra and Intraocular Muscles of Eyeball 1

Fig: Extra and Intraocular Muscles of Eyeball

Muscles of an eyeball with their actions and nerve supply are mentioned below:

Superior rectus Muscle

  • Action: Raises cornea upwards and medially. The main movement is elevation. Also contributes to adduction and medial rotation of the eyeball.
  • Nerve Supply: Oculomotor nerve

Inferior rectus Muscle

  • Action: Depresses cornea downward & medically. Also contributes to adduction and lateral rotation of the eyeball.
  • Nerve Supply: Oculomotor nerve

Medial rectus Muscle

  • Action: Rotates eyeball medially. And, adducts the eyeball.
  • Nerve Supply: Oculomotor nerve.

Lateral rectus Muscle

  • Action: Rotates eyeball laterally, and Abducts the eyeball.
  • Nerve Supply: Abducent nerve

Superior oblique Muscle

  • Action: Rotates cornea downwards and laterally. Depresses, abducts and medially rotates the eyeball.
  • Nerve Supply: Trochlear nerve.

Inferior oblique Muscle

  • Action: Rotates cornea upwards laterally. Elevates abducts and laterally rotates the eyeball.
  • Nerve Supply: Oculomotor nerve

Sphincter pupillae of iris

  • Action: Constricts pupil
  • Nerve Supply: Parasympathetic via Oculomotor nerve.

Dilator papillae of iris

  • Action: Dilates pupil
  • Nerve Supply: Sympathetic

Ciliary muscle

  • Action: Controls shape of the lens in accomodation (makes more globular)
  • Nerve Supply: Sympathetic.
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