Rectus Muscle

Any of four muscles of the eyeball that arise from the border of the optic foramen and run forward to insert into the sclera of the eyeball; medial rectus inserts into the medial (nasal) aspect of the sclera; lateral rectus inserts into the lateral (temporal) aspect of the sclera; superior rectus inserts into the superior aspect of the sclera; inferior rectus inserts into the inferior aspect of the sclera.