TMJ & Muscles of Mastication Flashcards
function of mandible with regard to muscles
site of attachment for muscles
what joins to form the mandible
a vertical ramus and horizontal body
2 processes of the mandibular body
coronoid process and condylar process
what is the condylar process
the articular process of the TMJ that consists of a head and neck
what is found between the 2 processes
the mandibular notch
what is the angle of the mandible
where the ramus and body meet posteriorly
what forms the prominent part of the chin
mental protuberance
what exits the mental foramen
mental nerve and associated blood vessels
what is the mandibular symphysis
where the 2 parts of the mandible fuse during development
what exits the mandibular foramen
the inferior alveolar nerve and accompanying artery and vein enter into the mandibular canal within the bone via this
what muscles attach to the mandible medially
mylohyoid and medial pterygoid
what muscles attach to the mandible inferiorly
infrahyoid muscles i.e. sternohyoid, sternothyroid, thyrohyoid, omohyoid
what muscles attach to the mandible laterally
masseter
what provides the boundary between the oral cavity and the neck
mylohyoid line and mylohyoid raphe
what happens if an abscess spreads below the mylohyoid line
it can cause Ludwig’s angina
why is mylohyoid line important in dentures
must stop short of mylohyoid muscle as contraction of it will move the denture when eating or speaking
why is the buccinator important in dentures
denture must stop short of oblique line otherwise buccinator will interfere with denture
mylohyoid groove
this is where the nerve to mylohyoid passes which is a branch of the inferior alveolar nerve which supplies the mylohyoid and digastric
where does the mandible articulate with the skull
at the mandibular fossa of the temporal bone just anterior to the external acoustic meatus
what forms the TMJ
the mandibular fossa of the temporal bone and condylar process of the mandible
what is the TMJ
a modified hinge (atypical) synovial joint
articular surfaces of TMJ are covered in
fibrocartilage NOT hyaline cartilage
what is unique about the TMJ
it is intrinsically unstable joint with anterior dislocation most common
2 extrinsic ligaments of TMJ
sphenomandibular and stylomandibular
name the 3 ligaments of TMJ
- sphenomandibular ligament
- stylomandibular ligament
- lateral ligament
intrinsic ligament of TMJ
lateral ligament
sphenomandibular ligament
primary passive support of the mandible. runs from spine of sphenoid to lingula of mandible
stylomandibular ligament
thickening of the fibrous capsule of the parotid gland. runs from styloid process to angle of mandible
lateral ligament
strengthens TMJ laterally and acts to prevent posterior dislocation with the postglenoid tubercle
when is TMJ most unstable
during depression
why is it most unstable during depression
condylar processes move anteriorly & lie underneath the articular eminences with the mandibular head then vulnerable to dislocation into the infratemporal fossa
5 movements of TMJ
- protrusion
- retraction
- elevation
- depression
- lateral
protrusion + retraction =
gliding movements between temporal bone and articular disc (superior cavity)
elevation + depression =
hinge & rotational movements of mandible and articular disc (inferior cavity)
lateral movements =
grinding & chewing
protrusion caused by
lateral pterygoid assisted by medial pterygoid and masseter
retraction caused by
posterior fibres of temporalis, deep part of masseter, geniohyoid and digastric
elevation caused by
temporalis, masseter, medial pterygoid
depression caused by
gravity, digastric, geniohyoid and mylohyoid
how does anterior dislocation happen
when head of mandible pass anterior to articular tubercles through excessive contraction of the lateral pterygoids
lateral movement caused by
temporalis of same side, pterygoids of opposite side and masseter
nerve supply of muscles of mastication
CN V3 i.e. mandibular division of the trigeminal
what are the 4 muscles of mastication
temporalis, masseter, medial pterygoid, lateral pterygoid
temporalis origin
temporal fossa & fascia
temporalis insertion
coronoid process of mandible (medial surface)
anterior border of ramus near last molar
temporalis function
retracts and elevates the mandible i.e. assists in closing the mouth
innervation of temporalis
deep temporal nerves from anterior trunk of CN V3
masseter origin
maxillary process of zygomatic bone
anterior 2/3s of inferior border of zygomatic arch (superficial head)
masseter insertion
at angle and lateral surface of the ramus of the mandible (superficial head)
masseter function
quadrate muscle that elevates the mandible
masseter innervation
masseteric nerve from anterior trunk of CN V3
medial pterygoid origin
from medial surface of lateral pterygoid (deep head) maxillary tuberosity and pyramidal process of palatine bone (superficial head)
medial pterygoid insertion
inserts into medial surface of ramus and angle of mandible
medial pterygoid function
elevates mandible and assists with lateral movements. also acts synergistically with masseter
medial pterygoid
quadrangular 2 headed muscle with a deep and superficial head
medial pterygoid innervation
by nerve to medial pterygoid from anterior trunk of CN V3
lateral pterygoid origin
infratemporal surface of greater wing of sphenoid bone (upper head)
lateral surface of lateral pterygoid plate (lower head)
lateral pterygoid insertion
inserts on to front of the neck of the mandible:
- pterygoid fovea for inferior head
- capsule of TMJ and articular disc for superior head
lateral pterygoid function
protrudes mandible, depresses mandible and assists medial pterygoid with lateral movements
lateral pterygoid innervation
by nerve to lateral pterygoid & buccal nerve from anterior trunk of CN V3
