Orbicularis oris

The orbicularis oris (Latin: musculus orbicularis oris) is a circular-shaped facial muscle that is located around the mouth. It is classified as the buccolabial facial muscle. The orbicularis oris is composed of two main parts, named the marginal (smaller) and peripheral parts (larger).

The marginal is the inner, while the peripheral is the outer part of the muscle. Superior and inferior aspects of both parts stretch between the right and left modiolus. The modiolus is a fibromuscular structure at each angle of the mouth. It is a connection site where several buccolabial facial muscles meet and blend with each other.

Origin

The fibers of the marginal and peripheral parts of the orbicularis oris muscle originate from the modiolus, skin of the mouth and other muscles of facial expression.

Insertion

Both parts of the muscle insert in the skin and mucous membrane of the lips.

Action

The orbicularis oris muscle closes the mouth and pushes the lips forward (protrudes the lips).

Innervation

Both parts of the orbicularis oris are innervated by the buccal branch of the facial nerve (CN VII).

Blood supply

The orbicularis oris is supplied with the arterial blood mainly by the superior and inferior labial branches of the facial artery, mental and infraorbital branches of the maxillary artery and transverse facial branch of the superficial temporal artery.