What are the extraocular muscles and what do they do?

The extraocular muscles are a group of muscles that control the movement of the eyeball and upper eyelid. They include seven voluntary muscles (six for eye movement and one for the eyelid) and three involuntary smooth muscles for assisting ocular and eyelid function.

How many extraocular muscles are there, and what are their names?

There are ten extraocular muscles in total. The voluntary muscles are: four recti (Superior, Inferior, Medial, Lateral), two obliques (Superior, Inferior), and the Levator palpebrae superioris for the eyelid. The involuntary smooth muscles are: Superior tarsal (Müller's) muscle, Inferior tarsal muscle, and Orbitalis muscle.

Which nerves supply the extraocular muscles?

Most extraocular muscles are supplied by the oculomotor nerve (CN III), except the lateral rectus by the abducent nerve (CN VI) and the superior oblique by the trochlear nerve (CN IV). A common mnemonic is LR6 SO4, rest by CN III.

What are the main actions of the extraocular muscles?

The extraocular muscles move the eye around three axes, with key actions such as: Superior rectus for elevation, adduction, intorsion; Inferior rectus for depression, adduction, extorsion; Medial rectus for adduction; Lateral rectus for abduction; Superior oblique for depression, abduction, intorsion; and Inferior oblique for elevation, abduction, extorsion.

What is the function of the levator palpebrae superioris muscle?

The levator palpebrae superioris is a voluntary muscle that elevates the upper eyelid. It has a skeletal part supplied by the oculomotor nerve and a smooth part (superior tarsal muscle) supplied by sympathetic fibers.

What clinical conditions are associated with extraocular muscle dysfunction?

Dysfunction can lead to conditions like strabismus or squint, caused by muscle paralysis and resulting in gaze deviation and double vision, and ptosis, which is drooping of the eyelid from nerve damage.

Where do the recti muscles originate and insert?

The recti muscles originate from the common tendinous ring at the orbital apex and insert anterior to the equator of the eyeball at specific distances from the limbus: Medial rectus at 5 mm, Inferior rectus at 6 mm, Lateral rectus at 7 mm, and Superior rectus at 8 mm.

Extraocular Muscles – Actions, Nerve Supply & Rules

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