Levator labii superioris alaeque nasi

The levator labii superioris alaeque nasi (LLSAN) is a paired facial muscle that extends from the root of the nose to the upper lip and the ala of the nose. It flares the nostrils and elevates the upper lip, enabling the "snarl" expression on the face. It can also produce expressions such as disdain, sneering, or showing the upper teeth. This muscle may be more prominent in some individuals, influencing the intensity of facial expressions.