L2 - Neuromuscular Determinant Flashcards
Two bones of the TMJ
Mandibular condyle Temporal bone (squamous part)
+ articular disc
description of mandibular condyle
general parts /shape
top of mandibular neck articulates with glenoid (mandibular fossa) convex elliptical shape medial and lateral poles
Temporal bone - which part and describe shape - what it determines
SQUAMOUS portion
articular eminence
- steepness and condylar guidance
roof of glenoid?
THIN - glenoid fossa is thin at top
TMJ does what movement?
HINGE and GLIDING
ginglymoarthrodial joint
2 types of joint movement occur
Gingylmoid = hinge Gliding = arthrodial = plane joint
Rotate? motion and where?
HINGING movement in the LOWER compartment
Translate? motion and where?
GLIDING movement in the upper compartment
ginglymoarthrodial joint
TMJ synovial type
two types of movement
rotating at hinge - ginglymoid
gliding at arthroidal
TMJ articular surfaces and implication
Fibrocartilage tissue
* fibrocartilage can withstand force of movements and it has a great ability to repair itself (as opposed to hyaline cartilage that does not)
LESS susceptible to the effects of aging and less likely to breakdown overtime
two differences in TMJ vs other synovial joints
TMJ does two movements and articular surfaces are covered by fibrocartilage
anatomy of the articular disc
biconcave fibrocartilaginous structure
flexible and can adapt to the functional demands
what does articular disc prevent?
prevents direct articulation of the condyle and temporal bone
the articulating surfaces of the two bone are incompatible so disc prevents from damage
anterior prominence of condyle where?
CENTRAL THIN PART OF THE DISC
posterior border of the articular disc?
at a 12 o’clock position on the condyle
function of synovial fluid
lubrication and nutrition
boundary lubrication vs weeping lubrication
boundary - lubrication continues - goes in and out of articular surfaces
weeping = lubrication when we keep closed
general characteristics of the ligaments of the TMJ
- fibrous connective tissue that connects two bones
- no active participation in the TMJ function
- passive restraining
- do not stretch
- extensive forces may cause elongation which will compromise the joint function
*ONLY restrict the excessive functions
capsular ligament superior? inferior? posterior? function?
superior? = attach temporal bone along the border of glenoid fossa and articular eminence
inferior?= attach to condyle
posterior?= postglenoid process
encompass the TMJ
function? –> retain synovial fluid inside
RESISTS any medial, lateral, or inferior forces that tends to dislocate the articular surfaces
Temporomandibular (lateral) ligament
location and function of outer oblique?
Outer oblique = is attached to the articular tubercule, and runs posterioinferiorly to the outer surface of the condylar neck
*LIMITS rotational opening (20-25 mm) and protects retromandibular structures
Temporomandibular (lateral) ligament
location and function of inner horizontal?
it is attached to the articular tubercle, runs anteriorposteriorly to attach to the lateral pole of the condyle and posterior part of the disc
FUNCTION: limits posterior movement of condyle and disc to protect the retrodiscal tissue
Under extreme force? : condylar neck fractures to prevent the condyle from entering the middle cranial fossa?
collateral (discal) ligaments
Attach?
Function?
Attach medial edge of the disc to the medial pole of the condyle and lateral edge of the disc to the lateral pole and lateral edge of the disc to the lateral pole
Function: allows disc to move passively with the condyle as it glides
Divides joint into superior and inferior cavities
Sphenomandibular ligament
attach and action
Spine of the sphenoid bone, runs downward and outward to lingula of the mandible
NO influence on mandibular movement
Stylomandibular ligament
attach
function
Styloid process to the angle and posterior border of the mandibular ramus
Limits excessive mandibular protrusive movement
functions of muscles of mastication?
muscles of mastication open, close, rotate, and protrude the jaw
enables to talk, chew and swallow
major muscles of masitcation
Temporalis
masseter
medial pterygoid
lateral pterygoid
Temporalis
Origin
Insertion
Function
Origin : Temporal fossa and lateral surface of the skull
Insertion: as a tendon into the coronoid process of the mandible
there are posterior, middle, and anterior portions
Function: close - elevate the jaw and retrudes mandible
Masseter muscle
Origin
Insertion
Function
Origin : from the inferior border and medial surface of the zygomatic arch
Insertion: into the angle and the ramus of the mandible
Function: powerful elevator (closure) of the jaw
+ the superficial part is involved in protrusion
medial pterygoid
Origin
Insertion
Function
Origin: from the pterygoid fossa of the sphenoid bone and the tuberosity of the maxilla
Insertion: into the medial surface of the mandible
Function: elevation and protrusion;
unilateral contraction causes mediotrusive movement
muscles that are primarily involved with mandibular protrusion?
INFERIOR LATERAL PTERYGOID
and
medial pterygoid
unilateral contraction of the medial pterygoid
mediotrusive movement
inferior lateral pterygoid
Origin
Insertion
Function*
Origin : on the lateral surface of the lateral pterygoid plate
Insertion : the pterygoid fovea of the condyle neck
Function: active during opening in conjunction with mandibular depressors and protrusion + UNILATERAL CONTRACTION = mediotrusive movement
action of infrahyoid muscles?
depresses the hyoid bone during swallowing
nerve innervations of masticatory muscles and TMJ?
Cranial nerve - V (trigeminal)
Facial Nerve - CN VII
anterior prominence of condyle?
opposes the central thin part of the articular disc
myotatic reflex - AKA
STRETCH REFLEX
- IMPORTANT IN DETERMINING THE RESTING POSITION OF THE JAW
- a sudden downward force is applied to the chin and activates muscle spindles - response is contraction in the massater muscle
Nociceptive reflex AKA
FLEXOR REFLEX
*REFLEX TO PAINFUL STIMULUS AND IS PROTECTIVE
it is activated by unexpectedly biting on a hard object.
elevators STOP CONTRACTING and DEPRESSERS START contracting to open the jaw
which ligament limits rotation?
TM ligament
condyle rotates up to 20-25 mm opening and tightening of the TM ligament limits the rotation
- the outer oblique portion
which ligament prevents further movement in translation?
Capsular ligament
condyle will translate up to maximum of 40-60mm opening and capsular will limit further
mandibular free opening movement is done by a combination of?
lateral pterygoid, geniohyoid, mylohyoid, digastric
mandibular free closing movement function of which muscles?
masseter, temporal, medial pterygoid
protrusion done by primarliy?
inferior lateral pterygoids
retrusion is protected by?
Capsular ligaments and the TM (lateral) ligament (more of the internal aspect)
what to ask when palpating the masseter and temporal muscles?
Is it the familiar pain (similar pain) that you are complaining about?
do you feel pain anywhere else?
significance in palpating the lateral pterygoid muscle
basic to jaw movement but NEARLY IMPOSSIBLE TO PALPATE
however if resist the patient when they go into protrusion and there is pain - this could be the source
range of motion and clinical implications of limited range of opening?
what is limited range?
limited range of motion is opening less than 40 mm and this indicates that there may be problems with the TMJ or muscles
range of motion in patients with an increased overbite?
in individuals with increased overbite- the amount of overbite should be added to the measured range of motion
lateral excursion range of motion
what is a limited value?
Any lateral movement that is less than 8mm is considered restricted
also note and account for any midline shift
protrusive movement range of motion
what is a limited value?
protrusive movement less than 8mm is considered a restricted movement
superior Aspect of lateral pterygoid function?
Active only with elevator muscles and during CLENCHING / power stroke
