TMJ. TMJ? TEMPOROMANDIBULAR JOINT The only joint in the head?
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Transcript of TMJ. TMJ? TEMPOROMANDIBULAR JOINT The only joint in the head?
TMJ
TMJ?
TEMPOROMANDIBULAR JOINT
The only joint in the head?
No
Type of the joint?
Synovial
Bone
Muscle
Ligaments
Innervation
Function
LEARNING OBJECTIVE
Describe the anatomical structures of the joint Explain the articulating surfaces of the bones Describe the embryology of the joint Identify: capsule, synovial membrane, ligament
and articulating disc Describe the muscles and the movements that
take place in the joint Describe the nerve and blood supply to the joint Explain how dislocation of the joint can occur
TMJ
Joint/ articulation? Connection between two separate parts of skeleton Mandible and the two temporal bones Craniomandibular joint Bilateral articulation the only visible movable joint in the head
Exercise Palpate the TMJ
Three articulating parts: Articular eminence (or tubercle) Articular fossae Mandibular condyle
Enclosed by fibrous connective tissue capsule
Mandibular condyle
Surface covered by thickened layer of fibrous connective tissue
Articular fossa and articular eminence
Articular fossa – non functioning portion
Articular eminence functioning portion Just anterior to the articular fossa Lined by thicker layer of fibrous tissue
Articular disc
Tough oval pad of dense ficrous connective tissue
Surface – smooth
Thinner in the centre than around the edges
Concave anteriorly to fit under the articular eminence
Convex posteriorly to conform to the shape of articular fossa
Flattened disc problems
Articular disc
Function: Partitioning the complex condylar movement into
upper and lower functional components Lubricating with synovial fluid Stabilising condyle Cushioning the loading Reducing physical wear and strains Helping regulate movements of the condyle
http://www.youtube.com/watch?v=4CVbHsnB3Rk
How does TMJ differ from other synovial joints?
TMJ develops between 8 – 14 weeks compared to 5-8 weeks for other synovial joints
TMJ – initially widely separated temporal and condylar blastema that grow towards each other
Limb joint develops to adulthood by cavity fromation within single blastema
Fibrous cartilagerather than hyaline cartilage
Embryology
10 – 12 weeks pc
Ossification of the temporal components begins independently of the events in the mandible
the condylar cartilage is present at the most superior aspect of the ramus.
the embryonic connective tissue (mesenchyme) between the growing condyle and temporal bone condenses to form the articular disc
Inferior compartment form first (10 weeks) , upper (11.5)
cavitation forms the lower joint compartment and then the upper compartment
14 weeks Joint development completed
Development
Infants: Articular fossa, articular eminence and condyle – flat About the same level as occlusal plane Why?
During development Articular fossa deepens Articular eminence - > prominent – when? Condyle becomes rounded
Growth Structure grow laterally – widening of the neurocranium Mature disc – changes shape, more compact, less cellular, more
collagen Condyle contains cartilage
After eruption of permanent dentition, articular tubercle becomes prominent
Accelerates until 12th year of life
Fibrous capsule Sheet/sac/tube of tissue Encloses the joint Fairly thin Lateral – temporomandibular ligament Attachment – upper – circumference of articular
fossa Lower – neck of the condyle
Two layers: Inner layer (synovial membrane)
Lines fibrous capsule Covers the bone Secretes synovia – lubricates and nourishes
Outer layer Thicker layer of fibrous tissue Accessory ligaments
Ligaments
Capsular ligament – restricts posterior movement of condyle Temporomandibular ligament
Attachment – upper – zygoma arch, lower – side and back of condyle neck
keeps condyle close to the fossa Helps prevent lateral and posterior displacement
Stylomandibular ligament Posterior to the joint Attached at the _____ and _____
Sphenomandibular ligament Medial to the joint Limit maximum opening Attached to ______ and _______
Articular disc Dense fibrous connective tissue Between mandibular condyle and articular
fossa/eminence Thinner – center
Anteriorly and laterally
Act as a buffer
Muscles
Muscles of mastication Masseter Temporalis Medial pterygoid Lateral pterygoid
Masseter
Most superficial, powerful
Quadrilateral
Origin: Zygomatic arch – inferior and medial surface and temporal process of zygomatic bone
Insertion: lateral surface of the ramus
Function: closes jaw, crushing
Temporalis muscle
Fan shaped, large but flat muscle
Origin: entire temporalis fossa (part of frontal and parietal bone, squamous part of temporal and greater wing of sphenoid)
Directed downward (anterior), downward, anteriorly (posterior part) – passing medial to zygomatic arch
Insertion: coronoid process, anterior border of ramus and temporal crest
Action: elevator, retractor
Medial pterygoid
Medial to ramus
Origin: medial surface of lateral pterygoid plate and pterygoid fossa, pyramidal process of palatine bone
Pass downward, laterally towards the angle of mandible
Insertion: medial surface of mandible in triangular region
Action: elevator
Lateral pterygoid
Horizontal fibres
Short, thick
Located in the infratemporal fossa
Prime mover of mandible except closing
Origin: 2 heads – upper head – infratemporal surface on great wing of sphenoid
Lower head – lateral side of pterygoid plate on sphenoid bone
Insertion: upper head – neck of condyle and anteroposterior surface of capsular ligament, into disc
Lower head – roughened pterygoid fovea on anterior surface of neck of condyle
Action: opening the jaw
Pulling articular disc and condyle forward down onto articular eminence
Innervation
Proprioceptive neurons in capsule and disc
Trigeminal nerve (cranial nerve V) – auriculotemporal branch of ______
Branches of mandibular division of the TN (auriculotemporal, deep temporal and masseteric) supply the joint
Blood supply
branches of external carotid artery
Ascending pharyngeal and superficial temporal branches
Anterior tympanic
Massteric
Middle meningeal branch of maxillary artery
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Problem
Dislocation • Extreme
opening of the jaw – laughing, dental treatment
Condyle moves too
far
Stuck in front of articular
eminence
Muscle spasm
RECAP
Name the bony components of TMJ?
Muscles that close the jaw
Nerve innervate the joint