Musculus depressor labii superioris
The depressor of the upper lip originates from the facial crest of the maxilla and inserts into the upper lip. It depresses the upper lip and works antagonistically to the levator labii superioris and other elevators. Innervation is via the ventral buccal branch of the facial nerve (CN VII). It contributes to the precise lip movements needed for selective grazing and manipulating objects. Like other facial muscles, it can be affected by facial-nerve trauma or paralysis.
Origin: Facial crest of the maxilla
Insertion: Upper lip
Action: Depresses the upper lip
Innervation: Ventral buccal branch of facial nerve (CN VII)
Rarely a primary concern. Facial-nerve lesions reduce its function along with other lip muscles. Asymmetric lip position warrants examination.
## Overview Lip motor dysfunction is loss of fine control of the lips, usually from facial nerve damage. The horse cannot sort feed or grasp small particles well, eats messily, and may have hay hangi
Difficulty manipulating feed with the lips or asymmetric lip movement should be checked by a veterinarian (dental and neurologic exam).
## Overview Lip motor dysfunction is loss of fine control of the lips, usually from facial nerve damage. The horse cannot sort feed or grasp small particles well, eats messily, and may have hay hanging from the mouth. The upper lip may appear stiff or immobile. ## Causes Facial nerve paralysis from trauma, pressure, or central lesions. ## Diagnosis Observation of eating and neurologic examination of facial movement. ## Treatment Treat the underlying nerve injury. Supportive feeding with easily grasped feeds. Many peripheral nerve injuries improve over time. ## Recovery and Prognosis Variable. Mild cases often regain useful function. Severe or central lesions may leave permanent deficits. ## Prevention Avoidance of facial trauma and careful halter use. Signs include: messy eating; inability to pick up small treats or grain; stiff or immobile upper lip; hay strands hanging from the mouth
Rarely a primary concern. Facial-nerve lesions reduce its function along with other lip muscles. Asymmetric lip position warrants examination.
Difficulty manipulating feed with the lips or asymmetric lip movement should be checked by a veterinarian (dental and neurologic exam).
See the Depressor of the Upper Lip on our interactive 3D horse model. Open 3D Model