Musculus zygomaticus
Slender muscle retracting the mouth angle caudally. Part of the EquiFACS coding system for equine facial expressions; activation indicates pain or distress.
Origin: Fascia over masseter muscle and zygomatic arch
Insertion: Angle (commissure) of the mouth
Action: Retracts the corner of the mouth
Innervation: Ventral buccal branch of facial nerve (CN VII)
Chronic activation is a recognized component of the Horse Grimace Scale, signaling underlying discomfort.
Chronic activation is a recognized component of the Horse Grimace Scale, signaling underlying discomfort. Signs include: Corners of mouth drawn back and tight; tension lines around the mouth; combined with orbital tightening and stiff ears.
See the Zygomaticus on our interactive 3D horse model. Open 3D Model