Extraocular muscles

Extraocular muscles (schematic) by Eshaan Mehmi

There are 7 extra-ocular muscles - 6 of each responsible for moving the eye ball and 1 is responsible for raising the eyelids.

Function of eye muscles

The extra-ocular muscles are:

Levator palpebrae Superioris (most superior extra-ocular muscle)

• Origin: lesser wing of sphenoid bone (superior-anterior to optic canal)
• Insertion: superior tarsus of the eyelid
  

  Lateral view of Eye muscles
  

  Frontal Section
• Function: raising the eyelid
• Innervation: superior division of the oculomotor nerve (CN 3).
• Unique feature: some of its inferior fibers are smooth muscle fibers - help with eyelid elevation. Innervated by post-ganglionic sympathetic fibers.

Rectus Muscles (superior, medial and lateral)

Origin: the common tendinous ring (all of the muscles)

Insertion: sclera (posterior to corneoscleral junction)

Function: the axis of the orbit and the axis of the eyeball aren’t the same

• Superior rectus: moves the eyeball superiorly and medially.
• Inferior rectus: moves the eyeball inferiorly and medially  
• Lateral rectus: abduction of eyeball
• Medial rectus: adduction of eyeball

Innervation:

• All except lateral rectus: oculomotor n. (CN 3)
• Lateral rectus: abducent nerve (CN 6)

Superior oblique: medial to the levator palpebrae superioris

• Origin: body of the sphenoid bone.
• Insertion: tendon pass through trochlea insert in sclera (deep to superior rectus).
• Function: abducts, depresses and rotates eyeball medially.
• Innervation: trochlear nerve (CN 4).

Inferior oblique

• Origin: anterior floor of the orbit (maxilla).
• Insertion: Runs posterolaterally crossing the inferior rectus insert in sclera (deep to lateral rectus)
• Function: abducts, elevates and rotated eyeball laterally
• Innervation: oculomotor nerve (CN 3)