Lecture 11 & 12 Flashcards
TMJ
Bones can develop directly from precursor connective tissue called ________- ( membrane bones or intramembranous ossification) or via an _________________ (cartilage bones or endochondral ossification).
mesenchyme, intermediate cartilage model
T/F - most bones of the body develop as cartilage bones, however many of the bones of the skull are membrane bones including maxilla, and most of the mandible.
True
T/F - Cartilage bones undergoing ossification are invaded by blood vessels and the cartilage matrix becomes calcified, which is then replaced by bone.
True
T/F - Once main parts of the bone has formed, it undergoes remodelling externally (interstitial growth) & also addition of bone from the surfaces (appositional growth)
False, it undergoes internal remodelling
In the case of long bones, some of the cartilage remains as a ____________________ which contributes to the growth of bone. When growth is complete the growth plate is gradually & ________ replaced by bone.
Growth plate between the shaft (diaphysis) and the ends (epiphyses), permanently
Some of the cartilage model is also retained at the ends of the long bones adjacent to the joint cavity as ___________. Unlike the growth plate articular cartilage in a healthy joint is retained throughout life.
Articular cartilage
T/F - In cartilage bones, osteogenic cells develop in the mesenchyme followed by bone formation.
False, its membrane bones not cartilage
T/F - There is no cartilage intermediate so no cartilage growth plate within the bone and membrane bones for the most part grow by appositional growth (i.e. addition of osteoblasts onto the surface plus remodelling)
True
T/F - joint cavities form when the mesenchyme in the region of the cavity breaks down.
True
T/F - If a region of mesenchyme remains in TMJ between two developing joint cavities, this will become the articular disc.
True
List the three types of joints
- synarthroses
- amphiarthroses
- diarthroses
Synarthroses are __________ joints, e.g. _____ in skull. Joint consists of fibrous tissue joining adjacent _______. The serrated edges of the adjacent bones means that there is only very slight movement so these joints are more rigid that they might first appear. These sutures are gradually replaced by bone.
immovable, sutures, periosteums
Articulation of teeth in the alveolae (sockets) are also a type of fibrous joint which permits intrusion into the socket & recovery during biting forces. This type of peg & socket joint is called ________
Gomphoses
T/F - amphiarthroses are partly moveable joints e.g. intervertebral discs
True
T/F - Diarthroses are immovable joints
False, they are moveable
Diarthorses have a cavity between the ends of the joints filled with lubricating ________. this is produced by cells in the ________ which line part of the joint cavity.
synovial fluid, synovial membrane
Joint cavities are essentially ____________ which means that they are different to the lumen of a hollow organ.
Spaces in connective tissue
T/F - synovial membrane forms at least part of the lining of the joint cavity which is not an epithelium but is a connective tissue structure
True
What does synovial membrane consist of?
An inner cellular region with two cell types and deeper vascular connective tissue.
T/F - Cells lining synovial membrane are an epithelium as they have a basement membrane and intercellular material between them.
False, they are not an epithelium because no BM,
T/F - Synovial membrane cannot be folded into elongated structures called synovial villi
False, they may be folded.
T/F - lining cells of synovial membrane produce and also absorb synovial fluid as well as debris in the joint cavity.
True
T/F - synovial fluid is a plasma transudate with added protein & mucin
True
T/F - Synovial fluid does not contain any cells
False, they may contain a small number of cells such as lymphocytes and other white blood cells.
List the different cells of the synovial membrane
- Phagocytic cells (type A)
- Secretory cells (Type B)
Function of phagocytic cells in synovial membrane?
Absorbs components of synovial fluid
Function of secretory cells in synovial membrane?
Transmits synovial fluid and adds protein & mucin.
the TMJ can be classified by its movement which involves both hinging and sliding - called a _____________.
Ginglymoarthrosis
T/F - On articular surface of the TMJ, the condyle and temporal bones are predominantly membrane bones as they do not have articular cartilage.
True
T/F - surfaces of condyle and articular fossa facing joint cavities that grow during development and for the first five years of post natal life via endochondral ossification have articular cartilage
True
T/F - remodelling occurs during growth and as a result of functional changes, tooth wear and loss or orthodontic treatment
True
T/F - progressive remodelling is decrease in bone, regressive remodelling are addition of bone to joint surfaces, sometimes at the expense of cartilage
False, other way around.
Articular surface of temporal bone is covered with _______ with a thin layer of underlying cartilage especially on the _________. This contributes to growth especially of the ________. The cartilage is gradually lost (usually before the condyle disappears) and is replaced by _______.
Fibrocartilage, articular eminence, articular eminence, fibrocartilage.
T/F - In children, there is fibrous tissue & deeper fibrocartilage covering the joint surfaces of condyle, articular fossa & articular eminence
False, its in adults
T/F - In very young individuals, the covering is fibrous tissue plus a specialized type of cartilage, which is involved in endochondral ossification at the end of the condyle & to a much lesser extent the mandibular fossa & articular eminence
True
T/F - endochondral ossification ceases when growth stops but the cartilage stays, without leaving a fibrous or fibrocartilage covering
False, endochondral ossification ceases, but the cartilage gradually disappears leaving a fibrous or fibrocartilage covering
T/F - Unlike the epiphyseal plates in long bones, cartilage production can be reactivated in the TMJ leading to remodelling of bony surfaces
True, this is comparatively minor as a result of normal wear and tear or from orthodontic manipulations, whilst certain pathologies can result in quite gross changes
T/F - lateral ligament is attached pretty far from the TMJ capsule
False, pretty closely attached
T/F - there is one medial ligament in TMJ capsule which plays a secondary role in joint stability
False, there are two medial ligaments
T/F - The TMJ capsule is a sleeve of dense fibrous connective tissue attached to the margins of the articular fossa of the temporal bone (glenoid fossa), to the edges of the disc and to the neck of the condyle
True
List the different stratas that the TMJ capsule is divided into:
- posterosuperior with elastin, elastin in the posterosuperior stratum may help reposition the condyle during jaw closure
- posteroinferior - predominantly dense thick collagen fibres
- anterosuperior and anteroinferior strata (finer collagen)
____________ lines capsule (but is not found elsewhere in wear & tear regions - articular surfaces and disc. A variable number of synovial villi may project from ______ into joint compartment. These are narrow folds of ___________ with small blood vessels and covered with _______.
Synovial membrane, synovial membrane, synovial membrane
T/F - lateral pterygoid muscle attaches to posterior part of capsule and neck of condyle
False, it attaches to anterior part
T/F - venous plexuses are a network of endothelial lined spaces which receive venous blood from adjacent muscles and the TMJ
True
T/F - pterygoid venous plexus is anterior
True
T/F - retrodiscal venous plexus is posterior which drains into pterygoid venous plexus
True
T/F - articular disc shape follows contours of joint and is thicker laterally than medially
False, it is thicker medially
The articular disc: there is an anterior thick region - __________________, then a thinner region - ______________, then a very thick _________________.
Anterior band/pes menisci, intermediate zone/pars gracils menisci, posterior band/pars posterior menisci
T/F - articular disc is fibrous tissue or fibrocartilage & usually has a fibrous covering although a cellular synovial membrane in the pars posterior has been described. In adults there are sparse blood vessels mostly at the periphery of the disc
True
T/F - Articular disc fibrocartilage includes lots of cells - fibroblasts (elongated) with chondrocyte like cells (more rounded) sometimes seen.
False, sparse fibroblasts
Anterior band - attached to articular eminence of temporal bone by ________________ & to condyle by _____________. There may be a heel like prominence on the lower surface - _____.
Anterosuperior stratum of capsule, anteroinferior stratum, HELA
____________ - between posterior slope of articular eminence & anterior articular slope of condyle when teeth are maximally intercuspidated (close packed position of articulation).
Intermediate zone
_________ - attached to the posterior slope of the mandibular fossa by the posterosuperior stratum & to the condyle by the posteroinferior stratum.
Posterior band
T/F - at birth the condyle is covered with fibrous tissue & superficial layer of cartilage
False, its deeper layer of cartilage
T/F - most of condyle in TMJ grows by endochondral ossification
False, membranous ossification (addition of osteoblasts to the bone surface but growth at the head of condyle is by endochondral ossification via this layer of cartilage)
T/F - endochondral ossification starts with chondrocytes forming from precursor cells (chondroblasts) in the fibrous layer
True
T/F - chondrocytes then move into the deeper layers as new chondrocytes form, accompanied by differentiation and maturation of these chondrocytes and changes in the cartilage matrix –> recognisable layers with gradual transition from one layer to the next.
True
List the layers of covering of condyle from joint compartment to bone:
- superficial vascular layer & underlying fibrous layer
- zone of young & resting chondrocytes.
- zone of flattened chondrocytes
- zone of hypertrophic chondrocytes
T/F - superficial vascular layer & underlying fibrous layer consists of fibroblasts in loose connective tissue with variable number of blood vessels and also contains chondroclasts
False, dense connective tissue, and chondroblasts
T/F - zone of young and resting chondrocytes are large round cells
False, they are small round cells
T/F - zone of flattened chondrocytes have chondrocytes dividing here and accumulate hence the flattening
True
T/F - the proliferative layer is sometimes used to describe the young and/or the dividing zone
True
T/F - zone of hypertrophic chondrocytes have small chondrocytes which divide further
False, they are enlarged chondrocytes and do not divide further
T/F - chondrocytes break down and fragment in zone of hypertrophic chondrocytes
True
T/F - the cartilage matrix calcifies, blood vessels and osteogenic cells infiltrate and the calcified cartilage matrix is replaced by bone (membranous ossification)
False, first part all true, except it is endochondral ossification
T/F - Zone of hypertrophic chondrocytes growth is single directional like long bones where most of the direction of growth is longitudinal.
False, it is multidirectional, unlike long bones.
T/F - multidirectional growth allows for flexibility of development in the best position for placement of the condyle in the articular fossa
True
T/F - Endochondral ossification continues to happen even when growth stops and the cartilage is gradually reduced to fibrous or fibrocartilage. Like the epiphyseal plates, cartilage production can be reactivation, leading to remodelling of bony surfaces.
False, endochondral ossification ceases when growth stops, and unlike epiphyseal plates, cartilage production can be reactivated.
T/F - just prior to birth & for a short time after (2 years or so) vascular channels develop in the cartilage which connect the vessels of the fibrous layer with vessels in the marrow spaces of the condyle.
True
T/F - vascular channels in cartilage remain after 2 years of age
False, they gradually disappear.
Lateral ligament in TMJ is closely attached to capsule
True
Two medial ligaments in TMJ play a secondary role in joint stability.
True
Describe TMJ capsule
A sleeve of dense fibrous connective tissue attached to the margins of the articular fossa of the temporal bone (glenoid fossa), to the edges of the disc and to the neck of the condyle
Describe the divisions of strata of the TMJ
- Posterosuperior with elastin. The elastin in the posterosuperior stratum may help reposition the condyle during jaw closure
- posteroinferior - predominantly dense thick collagen fibres
- anterosuperior & anteroinferior strata (finer collagen)
What is the TMJ capsule lined with?
Synovial membrane
What projects from the synovial membrane
Synovial villi may project from synovial membrane into joint compartment.
What are synovial villi?
Narrow folds of connective tissue with small blood vessels & covered with synovial membrane
Where does lateral pterygoid muscle attach?
Attaches to anterior part of capsule & neck of condyle
Describe the relationships of venous plexuses to the TMJ capsule
- Pterygoid venous plexus anterior to capsule
- Retrodiscal venous plexus posterior to capsule (this drains into pterygoid venous plexus)
The articular disc shape follows the contours of the TMJ
True
Articular disc is thicker laterally than medially
False, it is thicker medially
Describe the different sections of the articular disc
- Thick anterior region: anterior band/ pes menisci
- Thinner region: intermediate zone/ pars gracils menisci
- Very thick POSTERIOR BAND/ PARS POSTERIOR MENISCI
Articular disc is made of?
Fibrous tissue or fibrocartilage and usually has a fibrous covering although a cellular synovial membrane in the pars posterior
In adults, there are sparse blood vessels mostly at the periphery of the disc
True
What does fibrocartilage include in the articular disc?
Fibrocartilage includes sparse cells - fibroblasts (elongated). Some chondrocyte like cells (more rounded) may also sometimes be seen.
Anterior band attached to articular eminence of temporal bone by _____ & to condyle by _________.
Anterosuperior stratum of capsule, anteroinferior stratum
There may be a heel like prominence on the lower surface of anterior band called?
Hela
The intermediate zone is located at?
Between posterior slope of articular eminence & anterior articular slope of condyle when teeth are maximally intercuspidated (close packed position of articulation)
Posterior band is attached to the ____ by the _____ and to the condyle by ______.
Posterior slope of the mandibular fossa, posterosuperior stratum, posteroinferior stratum.
List the layers of covering of condyle from joint compartment to bone
- Superficial vascular layer & underlying fibrous layer
- Zone of young & resting chondrocytes
- Zone of flattened chondrocytes
- Zone of hypertrophic chondrocytes
What does superficial vascular layer and underlying fibrous layer consist of?
- Fibroblasts in dense connective tissue. Has a variable number of blood vessels which may be particularly obvious in the superficial layer.
- Also contains chondroblasts
Describe the zone of young and resting chondrocytes
small round cells
Describe zone of flattened chondrocytes
chondrocytes divide here & accumulate (thus the flattening)
What is the term proliferative layer used to describe?
It’s used to describe the young &/or the dividing zone
Describe the zone of hypertrophic chondrocytes
Chondrocytes enlarge but do not divide further.
Chondrocytes break down and fragment. The cartilage matrix calcifies, blood vessels and osteogenic cells infiltrate and the calcified cartilage matrix is replaced by bone. This process is called endochondral ossification.
When does endochondral ossification cease?
It ceases when growth stops and the cartilage is gradually reduced to fibrous or fibrocartilage. However, unlike the epiphyseal plates, cartilage production can be reactivated, leading to remodelling of bony surfaces
Regressive remodelling is?
Decrease in bone
Progressive remodelling is?
Addition of bone to joint surfaces, sometimes at the expense of cartilage
The articular surfaces of temporal bone are covered with?
Fibrocartilage with a thin layer of underlying cartilage especially on the articular eminence. This contributes to growth especially of the articular eminence. The cartilage is gradually lost (usually before cartilage over the condyle disappears) & is replaced by fibrocartilage
