Bones

2 Pages 479 Words

BONES OF THE TMJ
1. Temporal bone
2. Mandible- condyles

1. TEMPORAL BONE:
a. Articular eminence (most convex part of fossa: “high position”) and Articular fossa are the two articulating areas. They are located on the inferior aspect of the bone.
b. Post-gleniod process: bone on the distal area of the zygomatic arch

Front of rounded depression: Articular eminence
Depression: Articular Fossa
Back of rounded depression: Post-glenoid process


2. MANDIBLE
a. Articulating surface of condyle is coronal part
b. Anterior to the condyle is the coronoid process.
c. The Mandibular notch is the area in between the coronoid process and the condyle


THE JOINT CAPSULE:
a. Completely encloses the TMJ; wraps around the articular eminence and articular fossa superiorly, and wraps around the mandibular condyle (including the neck) inferiorly
b. Tough, fibrous CT
c. Nerve supply and rich blood supply: a lot of pain possible.

THE DISC
a. Fibrous, located between the temporal bone and condyle of the mandible on each side
b. Divides the TMJ into two spaces- synovial cavities
1. Upper synovial cavity
2. Lower synovial cavity
c. Membranes line the inside of capsule and secrete synovial fluid for lubrication





JAW MOVEMENTS:

TMJ is classed ginglymoarthrodial joint because it moves as a hinge while its rotating. GLIDES and ROTATES

Sliding of Jaw: correct name is translation
Protrusion: bringing lower jaw forwards
Retraction: bringing lower jaw backwards
Depression: lowering of lower jaw
Elevation: raising of lower jaw

Contracting Muscle Action
Lateral pterygoid ►UNILATERAL contraction: lateral excursion; as one side contracts, the other side flops out

►BILATERAL contraction: pulls mandible forward (protrusion) also, sliding or translation.


Temporalis muscles (posterior portion)
Retraction of mandible


Anterior suprahyoid
&
Lateral pterygoid ...