Musculus quadratus labii superioris, also known as the quadratus labii superior muscle, is a facial muscle located in the upper lip region. It is one of the muscles responsible for facial expressions and plays a significant role in the movements and positioning of the upper lip.
The musculus quadratus labii superioris originates from the infraorbital margin, which is a bony ridge under the eye socket, and inserts into the skin of the upper lip. It runs parallel to the nasolabial fold, which is the crease extending from the side of the nose towards the corner of the mouth.
When this muscle contracts, it functions to elevate and retract the upper lip, contributing to several facial expressions such as smiling, sneering, and snarling. It works in conjunction with other muscles, such as the levator labii superioris muscle and zygomaticus major muscle, to generate these movements.
The musculus quadratus labii superioris receives its nerve supply from the facial nerve, specifically the buccal branch. This nerve originates from the main trunk of the facial nerve, which arises from the brainstem.
Understanding the musculus quadratus labii superioris is important in the field of facial anatomy and plastic surgery as it helps to elucidate the underlying structures and mechanisms involved in upper lip movements and expressions.
