Temporomandibular Joint (TMJ) Flashcards
bony structure of the TMJ
Articualar eminence / tubercles
MAndibualr fossa
condyle
mandible
TMJ
site of articualation between the mandible and the skull
modified hinge joint
Three components of the TMJ’s modified hinge joint
the articular eminence and tubercles of temporal bone
mandibular fossa of temporal bone
the condyle of the mandible
where are the articular eminence and tubercles associated with TMJ?
On the temporal bone
purpose of the articular eminence on the temporal bone
limiting forward movement of the condyle
Mandibular Fossa of the temporal bone
unique part of the synovial joint where where it is COVERED WITH DENSE FIBROUS TISSUE WITH CHONDROCYTES - movement here and subjected to force, so we have extra protective layer of fibrous tissue
- more like fibro cartilage than hyaline
what is the posterior aspect of the mandibular fossa?
SQUAMOTYPMANIC (lateral) and PETROTYMPANIC (more medial) fissures - demarcating squamous and petrous portions of the temporal bone
the post-glenoid tubercle
borders of the mandibular fossa
lateral
medial
posterior
anterior
lateral border of mandibular fossa
zygomatic process of the temporal bone
medial border of the mandibular fossa
spine of the sphenoid bone
anterior border of the mandibular fossa
articular eminence
posterior border of the mandibular fossa
details
squamotympanic fissure (more lateral aspect)
Petrotympanic fissure - this is more medial
fissures that going across the boundaries of the squamous and petroud portions of the temporal bone
squamotympanic fissure
separates the mandibular fossa of the squamous portion of the temporal bone from the tympanic plate of the temporal bone
petrotympanic fissure
‘small island of petrous bone’ appears within the MEDIAL half of the suture and complicates the nomenclature. The medial half of the fissure BECOMES THE PETROTYMPANIC FISSURE adjacent to the small wedge of petrous temporal bone
what passes through the petrotympanic fissure?
branch of CN VII – the chorda tympani leading it into the INFRATEMPORAL FOSSA where it is positioned medial to the spine of the sphenoid and courses anteriorly to JOIN THE LINGUAL NERVE to which it contributes GVE, SA, and GVA fibers
mandibular condyle components
medial and lateral poles
neck of condyle
articular surface of the condyle *
long axis of condyles is angled how?
posteriorly
neck of the condyle
connects the condyle to the ramus of the mandible
articular surface od the condyle
DENSE FIBROUS TISSUE, WITH ISOLATED GROUPS OF CHONDROCYTES AND LITTLE SURROUNDING MATRIX
bone formation type of the condyles and how you know
INTRAMEMBRANEOUS ossification because it has isolates groups of chondrocytes on it
external oblique line
serves as attachment site for the depressor anguli oris and majority is on the body
mental foramen
note its location on the mandibular body - lateral and anterior
inferior to the second pre molar
Gonial angle
angle between the posterior part of the ramus and the inferior border of the body of the mandible
antegonial angle
junction of the ramus and body of the mandible
Digastric fossa
internal feature of the mandible
TWO - found on the anterior internal aspect just above the inferior border and they are small depression on either side of the midline and reflect the bondy origins of the ANTERIOR BELLY OF THE DIGASTRIC MUSCLE
Mental spine (genial tubercles) (MS)
internal feature of the mandible
lies in the middle superior to the digastric fossae.
there may be four separate spines or a fused spine
attached to the upper aspect of the spine is the ORIGIN OF THE GENIOGLOSSUS MUSCLE
attached to the lower aspect is the origin of the GENIOHYOID MUSCLE
attached to upper aspect of the mental spine
attached to the lower aspect of the mental spine?
origin of the genioglossus muscle
lower = origin of the geniohyoid muscle
sublingual fossa
shallow concavity above the mylohyoid line that accomodates the sublingual gland
submandibular fossa
located below the mylohyoid line and accomodates the submandibular gland
mylohyoid ridge/line
raised line that runs OBLIQUELY from the lateral aspect of the digastric fossae to the area below the lingual alveolar crest of the LAST MANDIBULAR molar it is the origin of the MYLOHYOID MUSCLE
mandibular foramen
is an oblique opening at the midpoint of the rectangular ramus of the mandible
a few millimeters below the occlusal line of the mandibular molars
mandibular canal
continuation of the mandibular foramen deep into the mandible
CARIES THE INFERIOR ALVEOLAR NERVE AND ARTERY to the mandibular teeth.
canal runs inferior and anterior through the body and ramus just below the roots of the mandibular teeth
cutaneous branches of the nerve and artery pass to the facial aspect of the mandible through the MENTAL FORAMEN
lingula
tongue-like projectoin of bone guarding the superoanterior border of the mandibular foramen.
could potentially interfere with anesthetic injections of the inferior alveolar nerve at the mouth of the mandibular foramen
attachement for sphenomandibular ligament
lingula on internal feature of the mandible
mylohyoid sulcus/groove
is a narrow groove that runs downward and forward from the inferior border of the mandibular foramen
NERVE TO MYLOHYOID MUSCLE IN THIS GROOVE
internal oblique line, or temporal crest
buttressing ridge of bone on the internal surface of the ramus
it begins indistinctly on the coronoid process and slopes downward and forward
what happens as the internal oblique line approaches the last molar?
divides to pass around the last molar, and the divisions becoming CONTINUOUS WITH THE BUCCAL AND LINGUAL ALVEOLAR CRESTS
the enclosed triangle is the RETROMOLAR TRIANGLE
retromolar fossa
depression between the anterior border of the ramus and the temporal crest
shape of articular disc and some details
bi-concave and this shape allows flexibility in the disc so it can conform during TMJ motion and results in the disc being self-centered
it is INTRAARTICULAR and fibrocadtilagenous and suspended within joint capsule to stay in place as the joint capsule divides into two separate spaces and disc suspended by the lamellae
articular disc divides..
divides the joint into two separate compartments - superior and inferior
superior and inferior sheets or lamellae
the disc is ATTACHED TO THE INNER PERIPHERY OF THE ARTICULAR CAPSULE BY THE SUPERIOR AND INFERIOR SHEETS/LAMELLAE that continue superiorly and inferiorly to blend with the walls of the capsular ligament
description of the superior and inferior lamella
superior is more elastic and the inferior is primarily collagen
joint capsule intrinsic ligaments of the TMJ
capsular ligament and the lateral/temporomandibular ligament
unique in that they are not completely separate structures but regions of the capsule - thickenings of the joint capsule
all synovial joints have fibrous capsule that encloses the joint surfaces
capsular ligament and the lateral/temporomandibular ligamen
reinforcements WITHIN REGIONS of joint capsule and they prevent excessive movements in the lateral and posterior directions
preventing dislocation posteriorly
extrinsic ligaments
stylomandibular ligament and sphenomandibular ligament
named for their attachements
stylomadnibular ligament
runs from the styloid process to the angle of the mandible and limits protrusion (coming from back so limits the protrusive movements)
sphenomandibular ligament
runs from the spine of the sphenoid to the lingula of the mandible
supports weight of the mandible and prevents excessive lateral movements of the mandible
movements of mandible
elevation(closing), depression (opening), protrusion, retrusion, lateral excursion (deviation)
Hinge and gliding at the TMJ
movements of the mandible
hinge = in the inferior os lower joint compartment
translation/gliding takes place in the upper joint compartmentn
upon opening both condyle and the disc translate forward to sit on the articular eminence
Temporalis muscle action bilateral unilateral innervation
muscle of mastication
attachments - temporal fossa and tip of coronoid process, ramus of mandible
action
bilateral - elevation, retrusion of mandible
unilateral - ipsilateral deviation and holds onto the position of the mandible
innervation - deep temporal branches
what covers the temporalis
covered by a thick sheet of fascia, the temporalis fascia
Masseter Muscle
attachments action bilateral unilateral innervation
muscle of mastication
attachments - outer and inner surfaces of the zygomatic bone and arch and angle, and lateral surface of ramus of mandible
action
bilateral - elevation, protrusion of mandible
unilateral - ipsilateral deviation
innervation - masseteric nerve
lateral pterygoid muscle
attachments action bilateral unilateral innervation
muscle of mastication
attachments
superior head - greater wing of sphenoid bone
inferior head - lateral pterygoid plate
both - capsule, disc, condyle
action
bilateral - depresses (opens) , and protracts mandible
unilateral - contralateral deviation
innervation - lateral pterygoid nerves
ONLY MUSCLE THAT OPENS/ DEPRESSES MANDIBLE
Medial pterygoid muscle attachments action bilateral unilateral innervation
muscle of mastication
attachments - lateral pterygoid plate, tuberosity of maxilla and medial ramus of mandible, inferior to the mandibular foramen - on internal aspect
action
bilateral - elevation, protrusion
unilateral - contralateral deviation
innervation - medial pterygoid nerve
medial and lateral pterygoid muscles both come off of?
lateral pterygoid plate
nerve supply to TMJ
Most of it is supplied by sensory branches of teh AURICULOTEMPORAL NERVE
and a smalll anterior portion is supplied by sensory fibers usually arising from the masseteric branches of V3
pain impulses from TMJ?
the posterior and posterolateral regions of the joint capsule contain free nerve endings and conduct pain impulses from the joint
*this is part of a feedback mechanism to protect against excessive mandibular movements
what is in the retrodiscal inferior lamella regarding nerves?
contains PROPRIOCEPTIVE MECHANORECEPTORS THAT DETECT CONDYLAR MOVEMENT AND POSITION
- also providing feedback on pain and forces/ pressure
blood supply to the TMJ
articular branches arise from the SUPERFICIAL TEMPORAL ARTERY to supply most of the joint
- this is a terminal branch from the external carotid artery
additionally there are small arterial twigs from muscular branches of the maxillary artery (also a terminal branch of the external carotid artery) that supply the ANTERIOR aspect of the joint
how would you reposition a dislocated mandibular condyle?
HAVE TO PUSH DOWNWARD PRESSURE FIRST TO GET BELOW THE ARTICULAR EMINENCE - then should re position itself
also have to do this one side at a time
muscles palpated in the TMJ region?
Temporalis and masseter
examine TMJ from anterior and posterior
anterior - just anterior to the ear
posterior - place fingers inside ears, and press gently anteriorly
