mandible and TMJ 3 Flashcards
while bone formation starts in temporal blastema, the condylar blastema is still
consists of undifferentiated bipotential periosteal cells with bipotential .
what are the differences betwenn condylar and epipphyseal cartilagesin long bone?
epiphyseal has
1) ordered columns of cartilaginous cells
2) well-defined, elongated columns of chondroblast
Unlike most synovial joints, the articular surfaces of which are covered with hyaline cartilage, the temporomandibular articulation is covered by a layer of
fibrous tissue
mandibular condyle has _____ growth capacity? its cartilage can proliferate in any combination of ____ and ____ directions
multidirectional
*superior and posterior directions (as needed to provide the best anatomic placement)
chondroblasts get entrapped as chondrocytes in a matrix made of?
proteoglycans and type II collagen
hypertrophy
increase in the size
*in this case, chondrocytes grow as they mature and get stuck in matrix
Following the production of this cartilage, endochondral ossification occurs and involves ?
mineralization of the cartilage, vascular invasion, loss of chondrocytes, and differentiation of osteoblasts to produce bone on the mineralized cartilaginous framework
progenitor cells in the perichondrium and periosteum overlying the condyle can differentiate into?
chondrocytes or osteoblasts
what are the five bone formation-related cell populations are present in the condyle?
progenitor cells chondrocytes hypertrophied chondrocytes osteoblasts osteocytes
Peripheral condylar cartilage has ____ cells that differ morphologically from
chondrocytes, osteocytes, and progenitor cells. they are surrounded by?
***what type of bone?
peculiar cells
chondrocyte-like appearance, but are
surrounded by eosinophilic matrix like osteocytes
**CHONDROID BONE
what is Chondroid bone ?
Where is it found?
specialized calcified tissue with morphological properties intermediate between those of bone and cartilage
**found in craniofacial regions, including the mandibular symphysis, alveolar bone, glenoid fossa, and mandibular condylar cartilage
what are the 3 phases of TMJ development?
(1) blastematic stage (weeks 7–8 of development)
(2) cavitation stage (weeks 9–11)
(3) maturation stage (after week 12)
What appears along with the chondrification of the mandibular condyle in week 9?
inferior articular cavity appears
Primary cartilage structures vs secondary cartilage structures?
- primary= epiphysis, synchondrosis, nasal septum, ethmoid, sphenoid
- secondary= condyle, coronoid, mid palatal suture, fracture callus
The ______ of the mandibular condylar cartilage is continuous with the ______ of mandibular ramus
The perichondrium of the mandibular condylar cartilage is continuous with the periosteum of the mandibular ramus
the fibrous layer of the periosteum continues as the _____ of the Mandibular Condylar Cartilage
articular layer
the osteogenic layer of the periosteum continues as the __________ of the Mandibular Condylar Cartilage
prechondroblastic layer
What are the layers of TMJ: superficial to deep?
Articular layer= most superficial Prechondroblastic layer Chondroblastic layer Hypertrophic layer Cartilage-bone interface
Articular layer of TMJ
- Continuous with fibrous layer of the periosteum
- Fibroblasts in a type I collagen matrix
- Some elastic fibers
- Very low cell turnover
Prechondroblastic layer of TMJ
- Continuous with osteogenic layer of periosteum
- Multipotential mesenchymal cells
- Sparse matrix contains type I collagen and proteoglycans (no type II collagen)
- Majority of cell divisions occur in this layer, especially in the rounded cells
Chondroblastic layer of TMJ
• Begins with lowest zone of flattened cells
• Considerably more matrix than
in prechondroblastic layer
• Matrix is rich in type II collagen and aggrecan
• Cells are not oriented in palisades/rows (like growth plate or cranial base) but have NO direct orientation
Hypertrophic layer of TMJ
Cells enlarge greatly, fill lacunae
• ***Matrix contains both type I and type II collagen, as well as type X collagen, a synthetic product specific to hypertrophic chondrocytes
• Deeper layers are mineralized
Cartilage-bone interface layer of TMJ
• Hypertrophic chondrocytes undergo apoptosis or metaplastic change into
osteoblasts
• Blood vessels invade, bringing with them cells that destroy cartilage matrix
• New bone is deposited in and around septa of cartilage matrix
what is synovial fluid?
- -produced by synovial membrane intimal cells
- -forms viscous fluid (plasma, protein, and mucin)
- -contains many varying types of cells
what does synovial fluid do?
- provides lubrication
- nutrition
- removes foriegn stuff
fibrochondrocytes synthesis? found?
found in articular discs; found in FIBROCARTILAGES
* synthesize BOTH type 1 and type 2 collagens AND proteoglycans
wwhat is Articular Disc
Fibroblasts and elastic fibers in a collagenous matrix
***avascular and aneural in loaded regions
In adults, both TMJ disc and knee meniscus are?
FIBROCARTILAGES
*in young ppl it is dense and irregular with condrocytes
