TMJ Histology Flashcards
What are the components of the TMJ?
Condyle
Disc
Ligaments
What anatomical structures make up the TMJ?
Temporal bone (articular eminence)
Mandible (condyle)
Article disk
Capsule and supporting ligament
What does the articular disk do to the TMJ?
The articular disc separates joint cavity into a superior synovial cavity and an inferior joint cavity. Superior cavity =gliding, inferior cavity = rotational movement when jaw opens initially.
How many ligaments support the TMJ?
4 ligaments: Stylomandibular and sphenomandibular
ligaments are accessory and are not directly attached to any part of the joint.
The stylomandibular ligament separates the infratemporal region (anterior) from the parotid region (posterior), and runs from the styloid process to the angle of the mandible.
The sphenomandibular ligament runs from the spine of the sphenoid bone to the lingula of mandible
What is the function of the TMJ?
Allows elevation + depression, protrusion + retraction, and lateral movement.
What type of joint is the TMJ?
Synovial joint. Main feature of synovial joint is the synovial fluid which is important for lubrication and protection of the joint. Hinge-like shape (not a pure hinge joint because it allows some gliding motion). Has a disk, 3 ligaments and 4 main muscles that created 5 types of motion.
What are the anatomical structures that make up the TMJ?
Temporal bone (articular eminence)
Mandible
Articular disk
Capsule + supporting ligaments
What is the clinical significance of the position of the TMJ?
External auditory meatus is right next to the TMJ meaning inflammation of the TMJ can affect hearing
What are the histological features of the TMJ?
Bones of the joint consist of 1 condyle, and 2 glenoid fossae and an articular eminence, articular disc, capsular ligament, and joint cavity consisting of synovial fluid.
What are the histological features of the mandibular condyle?
From top to bottom consists of: Articular fibrous layer, cartilage layer, calcification zone, compact cortical bone, and spongiosa.
What are the histological features of the articular disk in the TMJ?
Dens
Avascular
Tightly packed type 1 collagen fibrous tissue which run in anterio-posterior direction with few elastic fibers, fibroblasts and elongated process
Temporal bone is involved in translational movements and this is the secondary gliding motion of the jaw as it is opened widely.
What are the bones of the TMJ?
1 condyle
2 Glenoid fossae, articular eminence
What are the features of the articular disc?
TMJs are one of the only synovial joints in the human body with an articular disc.
Disc is composed of fibrocartilagenous tissue and is positioned between the 2 bones forming the TMJ
What is the articular disc made of?
Dense, avascular, tightly packed type one collagen fibrous tissue which run in anterio-posterior direction
Few elastic fibers
Fibroblast with elongated process
Chondrocyte with advancing age
What is the articular eminence made of?
Formed of spongy bone which covered by thin layer of compact bone.
Covered by thick fibers arranged in 2 layers:
Inner layer: Fibers are at a right angle to the bone surface
Outer layer: Fibers are parallel to bone surface
What does the temporal bone do in the TMJ?
Is involved in translational movement; Secondary gliding motion of the jaw as it is opened widely.
It makes the upper surface of the TMJ
What is the condyle of the TMJ?
The part of the mandible which makes up the under-surface of the disc. The part of the temporal bone which meets the upper surface of the disk is the glenoid fossa.
Where is synovial fluid produced?
Synovial membrane has intimal cells which produce a viscous fluid (plasma, protein, and mucin), containing varying types of cells (monocyte, lymphocyte, sometimes multi0nuclear leukocyte and macrophages)
What are the functions of the synovial fluid in the TMJ? (and other joints)
Provide lubrication to joint surfaces to reduce the
wear during joint function.
Provide nutrition to disc , articular surfaces.
Removal of foreign material (phagocytosis)
What makes up the temporomandibular ligament?
It has a thickened lateral portion and 2 parts:
Outer oblique portion
Inner horizontal
What minor ligaments support the TMJ?
Stylomandibular ligament: Separates the infratemporal region (anterior) from the parotid region (posterior), and runs from the styloid process to the angle of the mandible.
Sphenomandibular ligaments runs from the spine of the sphenoid bone to the lingula of mandible
What kind of degenerative changes affect the TMJ?
Age related changes associated with TMJ include; tick fibrous covering of condyle with chondroid changes, synovial folds and villi increase and become fibrotic, osteoporosis of underlying bone, ankylosis, dislocation.
How can TMJ dislocation be treated?
Dislocation of TMJ can be treated simply by making patient bite on something then pushing it posteriorly (it is a hinge-joint)
