orbicularis

Orbicularis is a term used in anatomy to describe circular muscles that form a ring around an opening or orifice, acting as a sphincter to constrict that opening. The word derives from Latin orbicularis, meaning ring-shaped or circular. In humans, the most prominent examples are the orbicularis oculi around the eye and the orbicularis oris around the mouth. These muscles are composed of skeletal muscle fibers organized in circular or near-circular patterns and are under voluntary control through the facial nerve.

The orbicularis oculi surrounds the eyelids and has two functional parts: the orbital portion, which closes the eye forcefully, and the palpebral portion, which closes the eye gently during blinking. Together, they contribute to eyelid protection, tear distribution, and the lacrimal pump that helps drain tears. The orbicularis oculi is innervated by the facial nerve (cranial nerve VII) and receives vascular supply from branches of the facial artery and other regional vessels.

The orbicularis oris forms a muscular ring around the mouth and functions as a sphincter for lip movement. It plays a key role in articulation, speech, swallowing, eating, and facial expressions such as puckering the lips. Like the orbicularis oculi, the orbicularis oris is innervated by the facial nerve and works in concert with adjacent muscles of facial expression to shape the mouth.

Clinically, dysfunction or paralysis of these muscles—most commonly due to facial nerve injury or Bell’s palsy—can impair eyelid closure, tear drainage, or lip movements. Cosmetic procedures and reconstructive surgery may target these muscles to alter appearance or restore function.