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Muscles of
mandible
By: Abdul Muhaimin (D11 A007)
Reference: Veterinary anatomy of domestic animal
(Book)
Mandibular muscles
• Comprise muscle of mastication and
superficial muscles of mandibular space.
• Innervated by mandibular nerve (trigeminal
nerve)
• Responsible for movement jaw (mastication)
• Covers mandibular space and hyoid apparatus
ventrally.
• Different species have their own structure of
muscle for mastication.
Mandibular muscle
• Muscle of mastication
– Masseter muscle
– Medial and lateral pterygoid muscles
– Temporal muscle
• Superficial muscles of mandibular space
– Digastric muscle
– Mylohyoid muscle
Muscle of mastication
• Masseter muscle
– Broad multipennate muscle
– Multiple tendinous intersections
• Origin
– From ventral border of zygomatic arch and facial crest
• Insertion
– On the lateral aspect of mandible
• Extend
– From facial notch to temporomandibular joint.
Masseter muscle
• In carnivores, it is separated into 3 layers
– Superficial, middle, deep (by tendinous sheets)
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Superficial portion is the strongest
Middle layer is the weakest
In pig, these three layers are firmly fused
Tendinous intersections are pronounced, forming
5 distinct parts in the ox.
• Change in fibre direction between each portion
increases masticatory force of this muscle
Masseter muscle
• In horse, it shows up to 15 tendinous
intermuscular strands which are orientated
sagitally and divide muscle into multiple
layers.
• Both sides masseter muscles act together will
force upper and lower jaw together
• Mandible can be move to the side of
contracting muscle (grinding in herbivores)
Pterygoid muscle
• Pass from palatine, pterygoid and sphenoid
bones to the medial aspect of mandible.
• Lateral pterygoid muscle is smaller than
medial one.
• In carnivores, both are fused at their origin
• Horse: medial pterygoid muscle is covered by
lateral one. Mandibular nerve passes across
lateral surface of medial pterygoid muscle
(separating 2 pterygoid muscles).
Pterygoid muscle
• Pterygoid and masseter muscles contract
bilaterally will raise mandible, but if working
unilaterally, will draw mandible to side of
contracting muscle.
• Lateral portion also able to move mandible
rostrally (mouth open)
Temporal muscle
• Size varying in different species depending size
fossa
• The strongest muscle of head in carnivores.
• Dolichocephalic dogs: temporal muscle meets
corresponding muscle of opposite side in
midline (form mid-line sulcus)
• Brachycephalic dogs: two muscles don’t meet,
no sulcus visible
Temporal muscle
• Ruminant: temporal muscle is indistinct but
visible in horse
• Horse: temporal muscle however do not well
developed compared to other masticatory
muscles.
• It raises mandible acting together with other
masticatory muscles.
Superficial muscle of mandibular space
• Assist muscles of mastication. Cover ventral
side of lingual muscles in mandibular space.
• Digastric muscle
– Single bellied muscle in domestic animal (except
horse)
– Horse: has caudal and rostral bellies
– Other domestic mammals: evolutionary bipartite
structure is indicated by a fibrous intersection.
Digastric muscle
• Rostral part is innervated by mylohyoid nerve
(branch of mandibular nerve)
• Caudal part by digastric branch of facial nerve
• In carnivores: it is strong single-bellied muscle
with delicate tendinous strands (mark division
between rostral and caudal portion)
• Ruminants: tendinous intersection between
two bellies is indistinct.
• Horse: rostral belly depresses mandible and
opens mouth
Mylohyoid muscle
• Form sling between inner surface of body of
mandible
• Innervated by mylohyoid nerve (branch of
mandibular nerve), assigned to mandibular
group
• Can also be seen as lingual muscle (its
function)
• Supports tongue and raises it towards palate