Flashcards in Lecture 2 Deck (18):
describe the masseter
originates in the zygomatic arch & temporal portion of zygomatic process; EXTENDS DOWN to lateral-lower border of mandible;
has 2 heads-->deep and superficial; superficial fibres run down and back (for protrusion) and deep re vertical (elevation)
what are the major skeletal components?
3. temporal bone
4. other bone structures like frontal and parietal bone, hyoid bone, sphenoid,
study slide 14
type of movement of tmj?
Hinge (ginglymoid joint)
Sliding (arthrodial joint)
Complex (Rotation and Slide)
bony attachments to articular discs?
Posterior Superior – Tympanic Plate (Post. Surface of the articular fossa)
Posterior Inferior – Posterior Inferior margin of the articular surface of the Condyle
Anterior Superior – Anterior margin of the articular surface of the Temporal Bone
Anterior Inferior – Anterior margin of the articular surface of the Condyle
describe the articular surface histoloy
articular zone-->dense fibrous CT with collagen fibres arranged in paralell to the art surface; fibrous CT less
proliferative zone-->cellular layer of undiff. mesenchymal cells;
fibrocartilagounous--– collagen fibrils arranged in crossing patterns > radial patterns
Random 3D arrangement – resists both compressive and lateral forces
Calcified cartilage zone – Deepest zone
This zone is where cells die, the cytoplasm is evacuated and the resulting scaffold is excellent for bone remodeling.
Endosteal bone growth proceeds as elsewhere in the body
describe vascularization of the TMJ
Posterior = superficial temporal artery
Anterior = middle meningeal artery
Branch of internal maxillary artery
Inferior = internal maxillary artery
Also important = deep auricular, anterior tympanic and ascending pharyngeal arteries
The Condyle = thru marrow from inferior alveolar artery
Also feeder vessels – enter directly into condylar head from ant. & post.
describe teh function and attachment of the collateral ligament
attach the articular disc (med. & lat.) to the condylar poles
Divides joint space into superior and inferior cavities
Prevents med./lat. movement of the disc, but allow ant./post. rotation (hinge movement)
Have vascular supply and are innervated (proprioception, movement and pain)
describe the function and attachment of the capsular ligament
Superior attachment – surrounds the mandibular fossa and articular eminence
Inferior attachment – neck of the condyle
Resists all movement med/lat or inferiorly
Retains synovial fluid
Innervation = proprioception
describe the function and attachment of the temporomandibular ligament
Two parts: outer oblique & inner horizontal portions
Outer oblique—portion responsible changes motion from hinge to translation at maximum tension
Somewhat acts like a sling
Outer oblique – from lateral border of articular eminence & zygomatic process posteriorly inferiorly to the outer surface of the condylar neck.
Resists excessive condylar dropping, limits extent and path of opening (rotation until lig. Is tight, then translation)
Inner horizontal – from lateral border of articular eminence & zygomatic process posteriorly (horizontally) to the lateral pole of the condyle & post portion of the articular disc.
Limits post. movement of condyle and disc (protects post. articular fossa, retrodiscal tissue, and lateral pterygoid from over extension)
If this portion gets affected, can affect position of articular discpopping and clicking in jaw
describe the accessory ligaments
Sphenomandibular – from sphenoid bone inferiorly to the lingula (no sig. effects on opening)
Stylomandibular - from styloid process inferiorly to post. Border of ramus of mand.
Tight on mandibular protrusion only (relaxed on mandibular opening)
describe the temporalis
Large fan-shaped muscle – originates in temporal fossa & lateral surface of the skull
Fibers converge as it passes under the zygomatic arch
Inserts on the coronoid process & ant. border of ascending ramus
Acts like a hook so temporalis can pull up
Divided into 3 portions based on fiber direction and fn.
Anterior – vertical fibers
Middle – oblique fibers run anteriorly
Posterior – almost horizontal above the ear
Complete contraction elevates mnd. and brings teeth into occlusion.
Partial contraction moves the mnd. In the direction of the muscle fibers.
Ant. = vertical
Med. = elevation and retrusion
Post. = mostly retrusion
describe the medial pterygoid
Originates in the pterygoid fossa – extends down, back and outward and inserts on medial surface of the angle of the mandible.
Forms a muscular sling with the masseter to support the angle of the mandible
Elevation of the mandible and occlusion of teeth
Protrusion of the mandible
Unilateral contraction = mediotrusive movement
Mediotrusive = towards the midline; moves one side towards the midline but must move the other side laterally
If left contracts—pulls the left side to midline
Won’t go purely lateral or medial some protusion
describe the lateral pterygoid
Inferior Lateral Pterygoid (80% Type I fibers)
Originates on lateral surface of the lateral pterygoid plate – extends back, up and out to insert on the neck of the condyle
Bilateral contraction = condyles pulled down articular eminence = depression / protrusion
Major muscle responsible for opening mouth (inferior belly of lat. Pter.)
Unilateral contraction = mediotrusive movement – mnd moves laterally, to the opposite side
Superior Lateral Pterygoid (80% Type I fibers)
Smaller than the inf. lat. pterygoid m.
Originates on the infratemporal crest of the greater sphenoid wing – extends horizontally, back and out to insert on the articular capsule and disc (esp med. 30-40%) & the neck of the condyle (60-70%)
Contraction – in conjunction with elevator muscles, esp. during power stroke of chewing = elevation in function
Posterior belly – originates from mastoid notch (of temporal bone) to run forward, down and in to the intermediate tendon attached to the hyoid bone
Anterior belly – originates in the digastric fossa on the lingual side of the mandible to run down and back to the intermediate tendon attached to the hyoid bone
Bilateral contraction against a supported hyoid bone (supported by suprahyoid and infrahyoid muscles) = depression & retrusion of the mandible (teeth brought out of contact)
Also work with the suprahyoid (muscle groups that originate above the hyoid) and infrahyoid (muscle groups that originate below the hyoid) to elevate the hyoid bone during swallowing.
The ‘hyoids’ (supra & infra), along with other muscles in the head and neck support and coordinate the movements of the mandible
describe the soft tissue attachments of the articular disk
Posterior – Retrodiscal Tissue (vascular and innervated)
Anterior – Superior Lateral Pterygoid
Ant/Post and Med/Lat – to the Capsular Ligament
study slide 48