Musculus mentalis
The mentalis originates from the incisive part of the mandible below the lower incisors and inserts on the skin of the chin. Its action is to raise and protrude the lower lip and wrinkle the chin skin. It is innervated by the ventral buccal branch of the facial nerve (CN VII). In horses, tightening or wrinkling of the chin can be a subtle sign of pain or stress.
Origin: Incisive part of the mandible below lower incisors
Insertion: Skin of the chin
Action: Raises and protrudes the lower lip; wrinkles chin skin
Innervation: Ventral buccal branch of facial nerve (CN VII)
Rarely a primary clinical problem. Relevant mainly as part of facial expression assessment during pain or stress evaluation.
## Overview Chin tension, or bracing against the bit with a tight jaw and rigid poll, is a behavioral sign that can indicate oral pain, dental discomfort, bit-related injury, or neck pain. It is not
## Overview Curb chain trauma is injury to the chin groove or adjacent soft tissues from an improperly fitted, overly tight, or harshly used curb chain. Lesions range from superficial abrasions and h
Chin tightening or wrinkling, especially with other signs of discomfort, can indicate pain. Note the overall context.
## Overview Chin tension, or bracing against the bit with a tight jaw and rigid poll, is a behavioral sign that can indicate oral pain, dental discomfort, bit-related injury, or neck pain. It is not a diagnosis but a clue that warrants investigation of the mouth, teeth, bit fit, and cervical region. ## Causes Dental sharp points or ulcers, poorly fitted bit, rider hand pressure, temporomandibular discomfort, or cervical stiffness can all produce a tense chin and jaw. ## Diagnosis Observation under saddle and at rest, oral examination, dental evaluation, and assessment of bit and bridle fit. Neck mobility is also checked. ## Treatment Correct the underlying source: float teeth, change or refit the bit, adjust rider contact, or treat neck pain. The tension usually resolves once the driver is removed. ## Recovery and Prognosis Excellent when the cause is identified and corrected. ## Prevention Regular dental care, appropriate bit selection, and light, consistent rein contact. Signs include: rigid jaw; bracing against the bit; tension in the chin and poll; resistance to softening
## Overview Curb chain trauma is injury to the chin groove or adjacent soft tissues from an improperly fitted, overly tight, or harshly used curb chain. Lesions range from superficial abrasions and hair loss to deep ulceration. Chronic pressure can produce thickening or depigmentation. ## Causes Excessive tension, rough or twisted chain, or poor adjustment that allows the chain to rise out of the chin groove. ## Diagnosis Visual inspection of the chin groove after removing the bridle reveals abrasions, ulcers, or scarring. ## Treatment Remove the offending chain, keep the area clean, and allow healing. Most lesions resolve in one to two weeks. Address bit and curb adjustment to prevent recurrence. ## Recovery and Prognosis Excellent once pressure is eliminated. ## Prevention Correct curb chain fit (flat in the groove, activated only when needed) and smooth materials. Signs include: abrasions or ulcers in the chin groove; hair loss; sensitivity when the curb is applied; scarring in chronic cases
Rarely a primary clinical problem. Relevant mainly as part of facial expression assessment during pain or stress evaluation.
Chin tightening or wrinkling, especially with other signs of discomfort, can indicate pain. Note the overall context.
See the Mentalis on our interactive 3D horse model. Open 3D Model