Muscle · Head

Superior oblique

Musculus obliquus superior bulbi

The eye muscle that runs through a pulley. It starts at the back of the orbit, runs forward along the upper inner corner to a small cartilaginous loop attached to the frontal bone, turns sharply backwards and outwards through it, and only then attaches to the top of the eyeball behind its widest point. That change of direction is the whole point: the muscle pulls from in front, but because the tendon is redirected, the eye behaves as though it were being pulled from the pulley itself. Its main job is to roll the top of the eye inward toward the nose, and it is the only muscle supplied by the trochlear nerve — the thinnest cranial nerve, and the only one that leaves the back of the brainstem.