LO 4 Flashcards
List the structures of the Temporomandibular Joint (TMJ)
- Temporal bone
- Mandible
- Joint capsule
- Disc of the joint
Describe the temporomandibular joint (TMJ)
- The TMJ is the articulation of the temporal bone and the mandible on each side of the head
- Temporal bone is a cranial bone that articulates with the facial bone of the mandible at the TMJ by way of the joint disc.
- bilateral
- allows for movement of the mandible for mastication, speech, and respiratory movements
- the most unique and complex set of joints in the body – both joints must always move simultaneously
What are the 2 distinct movements of the TMJ?
Rotation and translation - occur in the joint during mandibular opening and closing.
Describe the sensory innervation of the TMJ
Auriculotemporal and masseteric branches of the mandibular nerve( or third division)of the fifth cranial nerve- trigeminal nerve
What is the motor function of the TMJ?
Muscles of mastication
Describe the blood supply of the TMJ
- Branches of external carotid artery:superficial temporal branch+ maxillary artery
- Veins - superficial temporal, maxillary and pterygoid
Describe the articular eminence
- On the temporal bone, anterior to the articular fossa
- A smooth, rounded protuberance on the inferior aspect of the zygomatic process
Describe the Articular Fossa (aka Glenoid Fossa / aka Mandibular Fossa)
- Posterior to the articular eminence
- A depression on the inferior aspect of the temporal bone
- Posterior and medial to the zygomatic arch
- Posterior to the articular fossa is a sharper ridge - the postglenoid process.
The mandible articulates with each temporal bone at the articulating surface of the _________
head of the condyle
Describe the joint capsule of the TMJ
- A joint capsule completely wraps around and encloses the TMJ
- Superior - articular eminence and articular fossa
- Inferiorly - condyle (at the level of the condyle’s neck)
Describe the articular disc (meniscus)
- located on each side between the temporal bone and condyle
of the mandible - On sagittal section ,it appears like a cap on the mandibular condyle
- The joint disc divides the TMJ into two synovial cavities: upper & lower
- The synovial membranes inside the joint capsule secrete synovial fluid – clear, viscous fluid
- Posteriorly, 2 divisions - The upper division: is attched to the postglenoid process; The lower division: attaches to the neck of the condyle
What is a ligament?
- A band of fibrous tissue that connects bones
- In the TMJ, it prevents excessive retraction of mandible
What are the 3 paired ligaments of the TMJ
- Temporomandibular - major ligament; provides strength to the joint; prevents excessive retraction of mandible
- Stylomandibular - runs from styloid process of temporal bone to angle of mandible; becomes taut when mandible protrudes
- Sphenomandibular: not considered a part of TMJ; becomes taut when mandible protrudes; can prevent diffusion of local anesthetic agent during inferior alveolar nerve block.
What are the muscles of mastication responsible for?
- opening the jaws (depression)
- closing the jaws (elevation)
- moving the mandible forward (protrusion) and backward (retraction)
- shifting the mandible to one side (lateral
excursion /deviation) - These jaw movements involve the movement of the mandible—the rest of the skull remains relatively stable.
- Muscles of mastication work with the TMJ to accomplish these movements of the mandible
Describe the 2 basic movements of the mandible (performed by the TMJ and its associated muscles of mastication)
- Gliding (sliding)
- Rotational (hinge)
Describe gliding (sliding)
- Occurs mainly between the disc and the articular eminence of the temporal bone in the upper synovial cavity
- The disc plus the condyle move forward or backward, and down and up the articular eminence.
- The gliding movement allows the mandible to move forward or backward.
- Bringing the mandible forward involves protrusion of the mandible.
- Bringing the mandible backward involves retraction (retrusion) of the mandible
Describe rotational movement (hinge)
- Occurs mainly between the disc and the condyle in the lower synovial cavity
- The axis of rotation of the disc plus the mandibular condyle is transverse
- The movements accomplished are depression or elevation of the mandible
- Depression of the mandible lowers the jaw.
- Elevation of the mandible raises the jaw.
With these two types of movements, gliding and rotation, and with the right and left TMJs working together, the finer movements of the jaw can be accomplished. These include ___________
opening and closing the jaws and shifting the mandible to one side