Levator nasolabialis muscle

The nasolabial muscle is located on the side of the nasal region, from the root of the nose, medially to the orbit, until the upper lip and the wing of the nose.

Conformation: It is a thin and long strip with more or less parallel borders, nearly entirely fleshy in Men and Cats. In most Mammals, its dorsocaudal part is aponeurotic: this thin fibrous sheet merges with its opposite on the root of the nose and is in continuity between the orbits with the epicranial aponeurosis. The rostral part, always fleshy, stays simple in Men, Carnivorous, and Rabbits; a little beam, inconstant, arises from the caudal border in Ruminants to pass under the canine muscle. In Equidae, there are two distinct branches; the caudal one covers the canine muscle and the rostral, broader, passes under this muscle. Very broad and not well defined in Carnivorous, the nasolabial levator muscle is proportionally narrower and better isolable in Men, Equidae, Ruminants and Rabbits. It is much thiner in Bulls than in Equidae and very weak, if not absent, in small Ruminants. It is also very thin, nearly absent in Pigs.

Insertions: in Men, on the maxilla and the border of the nasal bone. In domestic Mammals, it starts by the uneven aponeurosis that extends the epicranial aponeurosis between the orbits; it also attaches by some fibers on the rostral part of the frontal bone, the base of the nasal bone, and, in Dogs, to the superior border of the maxilla. The extremity is done under the skin of the upper lip and of the wing of the nose, where the fibers merge with the ones of the orbicular muscle of the mouth and the canine muscle.

Relations: Covered by the skin, this muscle covers the maxilla and the levator labii superioris muscle and the canine muscle, that covers its rostral branch in Equidae.

Functions: It lifts the upper lip pulling it aside; it also pulls on the wing of the nose and participates to the nostril's dilatation.

Vessels and nerves: The arteries coming from the superior labial artery and of the ends of the facial artery (infra-orbital in Carnivorous, transverse of the face in small Ruminants). The motricity comes from the dorsal buccal branch of the facial nerve.