Superior rectus muscle

At a glance

English

Superior rectus muscle

Latin (TA2)

Musculus rectus superior

System

Muscle

Region

Head

Side

Paired, left and right

About the superior rectus muscle

The superior rectus is one of the four rectus muscles that move the eyeball, and it lies on top of the globe, under the levator palpebrae superioris. Like the other recti it runs from the apex of the orbit to the front half of the eye. Because the orbit points outwards while the eye looks straight ahead, its pull is angled to the visual axis, and that angle gives it extra actions besides lifting the gaze.

It arises from the upper part of the common tendinous ring, the fibrous ring at the orbital apex that surrounds the optic canal and part of the superior orbital fissure. It runs forwards and slightly laterally above the eye and ends in a broad tendon, about a centimetre wide, on the upper surface of the sclera in front of the equator, roughly eight millimetres from the corneal edge. Its sheath is joined to that of the levator above, so the upper lid rises as the eye looks up, and a thin fascial septum links it to the lateral rectus.

Its main action is to raise the eye. Because of its angle it also adducts and intorts it, turning the top of the eye towards the nose; the inferior oblique, acting with it, cancels that twist so the view stays level. Its lifting power is purest when the eye is turned outwards, and in that position it is the only muscle able to raise the gaze, so it is tested by asking the patient to look up and out. It is supplied by the upper division of the oculomotor nerve, which enters its lower surface, and by the superior muscular branch of the ophthalmic artery.

Weakness or paralysis follows lesions of the oculomotor nerve, from birth or after injury, and leaves the eye unable to look up properly. If the inferior rectus is weakened, for example by local anaesthetic in eye surgery, the superior rectus may overact and hold the eye too high; surgery to weaken or move the superior rectus usually helps. Blocked venous drainage near the muscle can make the eye bulge, visible on scans. Rarely it is absent from birth, and slips of the medial and lateral recti can be moved up to replace it.

Attachments, action and supply

Origin

Upper part of the common tendinous ring at the apex of the orbit.

Insertion

Upper surface of the sclera in front of the equator, about 8 mm behind the corneal limbus.

Action

Elevates the eye (most purely when abducted); also adducts and intorts it.

Nerve supply

Oculomotor nerve (cranial nerve III), upper division.

Blood supply

Superior muscular branch of the ophthalmic artery.