Temporomandibular Joint (Ch. 5)

TMJ articulation

mandibular condyles w/ temporal bone

TMJ

unique, most complex joint in human body; allows for
-chewing
-speech
-respiration

temporal bone

-articular fossa
-articular eminence
-zygomatic process
-postglenoid process

articular eminence

consists of smooth, rounded protuberance on inferior aspect of zygomatic process

articular fossa

depression on inferior aspect of temporal bone, posterior & medial to zygomatic arch

postglenoid process

sharper ridge posterior to articular fossa

mandible anatomy

-condylar heads
-fibrocartilage
-compact bone
-cancellous bone
-bone marrow & endosteum

mandible

articulates w/ each temporal bone @ heads of condyles of mandible w/ articulating surface of condyle

joint capsule

completely encloses TMJ; wraps around articular eminence & fossa & mandibular condyle

synovial joint

double lubricated cavity for smooth movement

joint motion

bilateral, mobile joint articulation of temporal bone & mandible
-synovial joint
-fibrous disk

fibrous disk

creates 2 synovial cavities, making it a double joint

TMJ ligaments

-temporomandibular ligament
-sphenomandibular ligament
-stylomandibular ligament

temporomandibular ligament

-lateral side of joint wrapped around capsule
-reinforcement of capsule
-prevents excessive retraction

sphenomandibular ligament

-medial side, from spine of sphenoid bone to lingula mandibular foramen
-landmark for inferior alveolar injection

stylomandibular ligament

medial side, from styloid process of temporal bone to angle of mandible

jaw movement of TMJ

combination of gliding & rotational movement

gliding movement

occurs b/w disc & articular eminence of temporal bone in the upper synovial cavity;
-protrusion & retraction of mandible

rotational movement

occurs b/w disc & condyle in lower synovial cavity;
-depressed & elevation of mandible

lateral deviation

combo of gliding & rotational

depression of mandible

lowering of lower jaw

elevation of the mandible

raising of mandible

muscles of mastication

-masseter
-temporalis
-medial pterygoid
-lateral pterygoid

free movement

interplay of masticatory muscles & morphology of teeth

masticatory movement

synergistic action of 3 groups of muscles

masseter

elevates jaw & clenches teeth w/ bi/lateral contraction of both sides

temporalis

retraction of mandible during elevation; elevates & retracts mandible, clenches teeth

medial pterygoid

elevates mandible; weaker than masseter

lateral pterygoid

lateral deviation of mandible is controlled by one muscle at a time; protrudes mandible & pulls articular disk forward- opens jaws

TMJ disorders

symptoms of tenderness, pain &/or muscle spasms associated w/ all 4 muscle groups

crepitus

an audible sound such as produced by the rubbing together of fragments of a fractured bone or by air moving in a tissue space

subluxation

acute episode of TMJ disorder in which both joints become dislocated often due to excessive mandibular protrusion & depression

temporomandibular disorder

disorder involving one or both TMJ

trismus

spasms of the muscles of mastication, resulting in inability to open or close mouth

myospasm

increased muscular tension & shortness that cannot be released voluntarily & prevents lengthening of muscles involved