ANATOMY - TMJ Flashcards
what are the muscles of mastication?
masseter
temporalis
lateral pterygoid
medial pterygoid
what is the masseter responsible for?
- elevation of the mandible
- protrude the mandible
roles of the temporalis
- anterior fibres elevate mandible
- posterior fibres retract mandible
2 components of the lateral pteryoid
- superior head
- inferior head
what is the role of the superior lateral pteryoid?
pull the capsule and disc forward during mouth opening
stabilises condyle during chewing
what is the role of the inferior lateral pteryoid?
depresses and protrude mandible
allows rotation of mandible
where is the medial pteryoid
sits deep to the masseter
role of the medial pteryoid?
- elevates the mandible
what bone do the muscles of mastication attach to? describe the different bones and where they are
sphenoid bone
describe the sphenoid bone and its components
what bone does the lateral pytergoid attach to?
sphenoid bone:
- lateral surface of lateral plate
- greater wing
what bone does the medial pytergoid attach to?
sphenoid bone:
-posterior surface of lateral plate
what is the structure of the TMJ?
the condyle of the mandible
- sits in mandibular fossa
- of temporal bone
- the joint capsule allows it to be synovial - keeps fluid in
- articular disc - allow movement without bone on bone contact
- articular tubercule - bony growth pushes the disc
what separates the TMJ into superior and inferior cavities?
articulator disc
- mandibular fossa
- articulator disc
- condyle
how can the TMJ move?
rotate
depress
elevate
protrusion
retraction
translational - everything moves at the same time
what movement happens within the inferior TMJ cavity?
rotation
what movement happens within the superior TMJ cavity?
protrusion-retraction movements
translation
which ligaments support the TMJ?
- joint capsule - contains synovial fluid and articular disc
- lateral ligament - ‘TMJ ligament’
accessory ligaments
- sphenomandibular ligament
- stylomandibular ligament
where does the joint capsule attach?
from temporal region superior and neck of mandible inferior ally
describe the lateral ligament
has two parts
- inner horizontal fibres
- super oblique fibres
what are the roles of the inner horizontal fibres - lateral ligament of TMJ?
- prevent excessive posterior displacement
- stops crushing of vascular tissue posterior to mandible
are the inner horizontal fibres - lateral ligament strong?
the neck would litttterally break before these fibressss jheeze
what are the roles of the outer oblique fibres - lateral ligament of TMJ.
- pushes the condyle as mouth opens onto articular tubercle
- limited stretch - prevent over-rotation
what is the articular tubercule also known as?
articular eminence
describe where they connect and the role of the accessory ligaments - sphenomandibular ligament (SML) and stylomandibular ligament (STML)
SML:
- from sphenoid to mandible
- support role of outer oblique fibres
- prevent excessive inferior displacement
STML:
- from styloid process to posterior ramus of mandible
- unclear function
- may limit excessive protrusion
role of the articular disc.
structure of the articular disc
- anterior capsular ligament - part of the joint capsule
- superior retrodiscal lamina - posterior and superior of the disc
- elastic - to push disc forward - inferior retrodiscal lamina - posterior and inferior of the disc
- not elastic - retrodiscal tissue
- highly vascular
- just posterior to disc
- essential to joint integrity - lateral and medial discal ligaments
- keep the disc close to the condyle - superior and inferior articular cavity
- superior is larger
how does the articulator disc move when opening and closing the mouth? 9 steps
- at rest
- mandibular fossa, disc and condyle in close proximity - lateral pteryoid - inferior head
- rotates mandible anterior - disc pushes anteriorly towards articular tubercle
- lateral pteryoid - superior head relaxed
- mandibular head resting on articular tubercle
- superior retrodiscal lamina
- pulls disc posterior during closing
- until all elastic tension removed - lateral pterygoid - superior head
- contracts to slow down anterior posterior movements - lateral pterygoid - inferior head relaxed
- disc back into place and in rest mode
how can the articulator disc be involved in temporomandibular clicking?
- disc is sat anterior
- mandible is seated posterior to it - normal movements
- mandible head snaps onto the articular disc
- instead of moving with it - normal movements back
- disc is still left forward
- mandible head clicks off the disc posteriorly
why does jaw locking happen?
loss of retrodiscal tissue elasticity pulling the disc back into place
- disc is already sat anterior
- mandible is posterior
- disc goes beyond articular eminence
- mandible head does not snap back into correct position
- opening of mouth is restricted
there are no normal phases
define myotactic
the reflex contraction of a muscle when an attached tendon is pulled
describe the myotactic jaw reflexes.
- detected when stretched
- afferent fibres send information through trigeminal nerve
- to trigeminal mesencephalic nucleus
- relay information
- efferent fibres sent signal to contract the jaw
describe the nociceptive jaw reflexes
protects the teeth from damaging biting forces
- pain from teeth
- afferent fibres to trigeminal nuclei
- 2 responses: excite mylohyoid muscle to open jaw and inhibitory signals to masseter to stop contracting
- relieve mouth of pain
