Download Masticatory Muscles

MUSCLES of MASTICATION
Prof. Peter Stanko, MD, PhD
Oral and Maxillofacial Surgeon
Dpt. of Stomatology & Maxillofacial Surgery
Comenius University, St Elisabeth Hospital
MUSCLES of MASTICATION
The muscles that move the mandible (lower
jaw) are also known as masticatory muscles
because they are involved in bitting and
chewing.
Through chewing, or mastication (Lat. masticare
= to chew) the tongue manipulates food and the
teeth grind it.
Movements in TMJ
1. Elevation (adduction, closing of the mouth)
2. Depression (abduction, opening of the mouth)
3. Protraction (propulsion, movement of the mandible forward),
it must be preceded by a mild mouth opening
avoid overjet of the upper frontal teeth)
4. Retraction (retropulsion, , movement of the mandible backward)
which has minimal extent (above 1 mm)
5., 6. Lateropulsions
i. e. sinistropulsion (movement to the left) and
dextropulsion (movement to the right).
Elevation of the mandible and other actions
(functions) of the masticatory muscles
1. Elevation of the mandible i. e. mouth closing is the general
action (function) of the masticatory muscles.
= Adductio (with exception of the pterygoid lateral muscle)
→→→ elevators.
2. Oposite the group of suprahyoid muscles
(musc. digastricus, musc. geniohyoideus, musc. mylohyoideus,
musc. stylohyoideus) depresses the mandible
i. e. they have function to open the mouth.
= Abductio (with exception of the stylohyoid muscle)
→→→ depressors.
1./ Musc. masseter
a/Pars superficialis
(origin = os zygomaticum and maxilla;
lower insertion = tuberositas masseterica),
course: oblique (backward)
b/Pars profunda
(origin = arcus zygomaticus; insertion = ramus
mandibulae), course: vertical;
Action of the masseter muscle
– elevates the mandible (Lat. adductio, closing mouth),
assists in protracting (Lat. propulsio) of the mandible
2./ Musc. temporalis
a/Mesial part
(origin = lamina superficialis fasciae temporalis;
insertion = proc. muscularis or coronoideus
mandibulae), course: vertical
b/Distal part
(origin = squama ossis temporalis;
insertion = proc. muscularis or coronoideus
mandibulae),
course: oblique (mesially);
Action of the temporal muscle
– elevates the mandible + retraction (Lat. repulsio)
3./ Musc. pterygoideus medialis
Origin = tuber maxillae;
Insertion = tuberositas pterygoidea
mandibulae), course: vertical (more exactly
oblique downwards laterally);
Action of the pterygoid medial muscle
– elevates the mandibulae + moves it from side
to side (Lat. lateropulsio) → active is the medial
pterygoid muscle from the opposite side
4./ Musc. pterygoideus lateralis
Origin = ala major ossis sphenoidalis, lamina
lateralis proc. pterygoidei;
Insertion = fovea pterygoidea on the condylar
process of mandibulae), course: horizontal;
Action of the lateral pterygoid muscle
– protraction of the mandibulae
(bilaterally or unilaterally → active is the lateral
pterygoid muscle from the opposite side).
INNERVATION of masticatory muscles
Innervation of all masticatory muscles
is supplied by mandibular division
of the trigeminal nerve (n. V./3).
BLOOD SUPPLY of masticatory muscles
Blood supply of masticatory
muscles
= by a. maxillaris (end branch
of a. carotis externa)
-pars mandibulartis
-pars pterygoidea
(-pars pterygopalatina...more
for supply of maxilla, palate,
nose + orbit ).
INFLUENCE of the masticatory muscles
on DISLOCATION
● The two groups of muscles (elevators,
depressors) together with extrinsic tongue muscles
may have influence on dislocation of bone
fragments of the mandible by injury.
● The influence of muscles on dislocation by
maxillary fractures is minimal, because muscles of
the facial expression are gentle.
► The dislocation depends on insertion site
of the certain muscle or muscles.
UNFAVORABLE vs. FAVOURABLE
course of fracture line in mand. angle
Vertical dislocation of frontal fragment
of the mandible (traum. open bite)
Suprahyoid muscles
(abductors)
Horizontal dislocation of frontal fragment
of the mandible
Musc.
GENIOHYOIDEUS