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-Origin: paracondylar process of occipital bone
-Origin: paracondylar process of occipital bone
-Insertion: angle of mandible
-Insertion: angle of mandible
-Two bellies: caudal half from the second visceral arch innervated by facial nerve (CV VII)
-Two bellies: caudal half from the second visceral arch innervated by facial nerve (CN VII)
cranial half from the first visceral arch innervated by the mandibular branch of the trigeminal (CV V3)
cranial half from the first visceral arch innervated by the mandibular branch of the trigeminal (CN V3)
-Herbiverous species have a limited digastricus muscle
-Canids have a larger digasticus muscle (but smaller in comparison with jaw closing muscles)
'''Jaw Closing Muscles'''
All jaw closing muscles derivie from the first visceral arch and are innervated by the mandibular branch of the trigeminal nerve (CN V3)
*Masseter muscle
-Origin: maxilliary region of skull and zygomatic arch
-Insertion: wide area on caudal side of mandible
-Several divisions
-Unilateral and bilateral contraction
-Also protrudes jaw
*Lateral Pterygoid muscle
-Origin: pterygopalatine region of skull
-Insertion: lateral aspect of mandible
-Also protrudes jaw (one-sided contraction)
'''Jaw Closing Muscles'''
*Medial Pterygoid muscle
-Origin: pterygopalatine region of skull
-Insertion: medial aspect of mandible
-One-sided contraction to close jaw
*Temporal muscle
-Origin: lateral surface of cranium
-Insertion: coronoid process
-Pulls mandible dorsally
-Also pulls mandible rostrally (overbite) and caudally (underbite)
'''Lateral Translation of Mandible'''
*Masseter muscle
*Contralateral medial and lateral pterygoids
==Jaw Articulation==
==Jaw Articulation==
==Species Differences==
*Large masseter and pterygoid muscles in the horse for extensive chewing
*Large temporalis muscle in the carnivores for snapping the jaw shut, e.g. in lions and pitbull terriers
*Herbiverous species have a limited digastricus muscle
*Canids have a larger digasticus muscle than herbivores (but smaller in comparison with jaw closing muscles)