Levator labii superioris, also called quadratis labii superioris, is a mouth muscle that is responsible for elevating the upper lip which makes it critical to the formation of normal facial expression as well as speech and nonverbal communication. A characteristic of the facial levator muscles are that they insert at the dermis, rather than in bone as is common with the majority of other muscles in the human body.

Levator labii superioris arises from the maxilla and zygomatic bones just below the orbit and inserts in the fleshy muscle and dermis of the upper lip. It is comprised of three distinct heads: angular head, intermediate head, and lateral head. The angular head emerges from the frontal process of the maxilla inferiorly forms a medial and lateral section. The intermediate head arises from the inferior part of the orbit and joins with muscle fibers from orbicularis oris. The lateral head emerges from the zygomatic bones and also joins with fibers of orbicularis oris but more laterally than the intermediate head.

When levator labii superioris contracts, it raises the upper lip and pulls on the sides of the mouth which results in a slight smirk. Injury to this muscle will cause deficiency in facial expression and thus significantly impact a patient’s life.