TMJ Flashcards
What type of joints generally permit very little movement?
Fibrous joints
Give three examples of Fibrous joints
- Suture (in the skull)
- Tooth socket (gomphosis)
- Syndesmosis (plural syndesmoses)
What is a syndesmosis?
Immovable connective tissue holding bones together (tibia and fibula)
Other than fibrous joints, what other type of joint permit very little movement?
Cartilaginous joints
What are the two types of cartilaginous joints?
- Primary
2. Secondary
What is a primary cartilaginous joint?
- Synchondroses
- Bone and cartilage in direct apposition (sternocostal junction)
What is a secondary cartilaginous joint?
- Symphyses
- Fibrous tissue internally in the joint
What type of joints are typically thought of as moving parts?
Synovial joints
Synovial joints consists of what?
A capsule filled with synovial fluid contained in a synovial membrane
What type of joint is the TMJ?
- Synovial
- Specifically a synovial sliding-ginglymoid joint
The TMJ articulation is composed of what?
- Condyle
- Mandible
- Glenoid fossa
More than opening and closing, the TMJ can perform what other types of movements?
Combinations of:
- Protrusive
- Extrusive
- Retrusive
What provides the track that the condyle slides along?
The glenoid fossa
What binds the condyle in the fossa anteriorly?
Articular eminence
*Condyle moves in front of it when the jaw opens
The ______ is able to rotate and translate in various ways
Condyle
The synovial cavity is divided into two compartments by what?
the articular disk
What are the two compartments of the TMJ?
- Upper joint cavity (adjacent to glenoid fossa)
2. Lower joint cavity (adjacent to the condyle)
T/F The articular disc is a distinct structure in the TMJ
False, it is effectively an extension of the synovial capsule
The articular disk runs between two bones, then flares outwards in sheets, attaching to both the ___ and the ______, and thus envelopes the joint.
- Condyle
2. Glenoid fossa
Mandible forms by _________ ossification and is associated with what type of cartilage?
- Intramembranous
2. Meckels
Meckel’s cartilage forms the _______ directly and articulates with the ________. This forms a primitive _________ joint before the development of the condyle and temporal bone
- Malleus
- Incus
- Primary
Articulation between the temporal bone and then forms the TMJ is what type of joint?
Secondary
The articular surfaces of the joint are covered with what?
Fibrous connective tissue
*This is different from hyaline cartilage
What is the fibrous covering of the condyle known as?
Lamina splendens
Describe the lamina splendens
A layer of mostly avascular type I collagen with smattering of fibroblasts scattered around
The glenoid fossa is covered by a ________ attached directly to the _____, while the articular eminence is overlaid by ________
- Thin fibrous layer
- Temporal bone
- Thicker fibrous layer
T/F There is a significant amount of cartilage associated with the articular surfaces of the joint proper
False, but there is some to be found deeper into the condyle and the articular eminence
The layers of cartilage found deep in the condyle and articular eminence have a layer of progenitor cells with spawn ______, which then secrete _____ containing ______ around themselves
- Chondroblasts
- ECM
- Type II collagen
Once the chondroblasts do their thing, they form _______ chondrocytes, which in turn undergo ________ ossification and leave a layer of __________
- Hypertrophic Chondrocytes
- Endochondral
- Fibrocartilage
The formation of the hypertrophic chondrocytes and the endochondral ossification happens at what stages in life for each relevant part of the joint?
- Occurs early in life in the articular eminence
2. Condyle it happens around the age of 30
The mandible is formed by intramembranous ossification but it is fair to say that the articular part of the TMJ is formed by _________
Endochondral ossification
What does the joint capsule form for the TMJ?
The dense collagenous sac that the joint is located within
The capsule has thickened regions which branch out to form _______
the temporomandibular ligament
What does the tempormandibular ligament do?
Most important for restricting lateral and medial movement when the joint articulates
The temporomandibular ligament restricts movement in 3 planes. What are they?
- Medial-lateral
- Superior-inferior
- Posteriorly
Name to other ligaments in the TMJ that limit the inferior movement of the joint when the jaw is open
- Spenomandibular ligament
2. Stylomandibular ligament
Posteriorly and anteriorly the articular disk is ______, leaving the condyle to rest on the thinner middle section when the jaw is closed
Thicker
The articular disk is totally continous with the _________
Joint capsule
The articular disk is a dense ______ structure and forms a surface for the head of the condyle to slide along when the jaw opens
fibrous
In the articular disk, there is a _______ network that overlays _______ cells
- Collagen fiber
2. Fibroblast
The joint capsule is lined by the ______, and contains a number of folds, which form _____ projecting into the joint cavity
- Synovial membrane
2. Villi
What are the two layers of the Synovial membrane?
- Subintima
2. Intima
Describe the subintima
- Layer of loose CT containing elastin fibers and supporting vasculature
- Contains various cells including macrophages, adipocytes, fibroblasts, mast cells and possibly others
- It is more or less continuous with the fibrous tissue of the capsule
Describe the intima
- Innermost layer of synovial membrane
- Contains several layers of the synovial cells
Name the two types of synovial cells that can be found in the intima
- A cells
2. B cells
Describe the A cells in the synovial membrane
Resemble macrophages
Describe the B cells in the synovial membrane
Like fibroblasts but contribute proteins found in the synovial fluid
Describe the synovial fluid itself
Basically blood plasma, containing extra proteins and proteoglycans
Name the 4 muscles of mastication
- Masseter
- Temporalis
- Medial pterygoid
- Lateral pterygoid
