Corpus: Medial rectus muscle

The medial rectus muscle is a skeletal muscle that is part of the extraocular muscles responsible for eye movement.

The medial rectus muscle originates from the common tendinous ring (annulus tendineus communis). It runs straight forward along the nasal orbital wall and attaches to the medial surface of the eyeball (bulbus oculi), just in front of the equator of the eye.

The medial rectus muscle is innervated by the inferior branch of the oculomotor nerve (cranial nerve III).

The muscle receives its arterial blood supply from the muscular branches of the ophthalmic artery.

Contraction of the medial rectus muscle causes inward rotation (adduction) of the eyeball. When the eye is in a strong upward gaze, the muscle also contributes slightly to elevation, and in a downward gaze, it contributes slightly to depression.