The orbicularis oculi is a large muscle that completely surrounds each orbital orifice and extends into each eyelid (Fig. 8.57). It closes the eyelids. It has two major parts:
The outer orbital part is a broad ring that encircles the orbital orifice and extends outward beyond the orbital rim.
The inner palpebral part is in the eyelids and consists of muscle fibers originating in the medial corner of the eye that arch across each lid to attach laterally.