mandible and TMJ 2 Flashcards
cells in the proximal part of the mandible have the potential to become either? and are therefore called?
osteoblasts or chondrocytes
*they are called osteochondroprogenitor cells
mandible growth until birth is influenced by the appearance of 3 secondary cartilages?
*called secondary why?
(1) the condylar cartilage,
(2) the coronoid cartilage;
(3) the symphyseal cartilage
* *SECONDARY to distinguish them from the primary Meckel’s cartilage; appear LATER in devel than primary
secondary cartilages develop as a result of what?
stresses and strains in the intramembranous bone, NOT by interactions with epithelium
Like many cephalic cartilages, secondary cartilages develop from?
mesenchyme of ectodermal origin (neural crest)
what secondary cartilage is carrot shaped?
condylar
condylar cartilage is what part of mand?
type of ossification?
remant?
1) ramus, appears at 12 weeks
2) endochondral
3) leaves thin layer of cartialge at 20 weeks in utera that lasts until the end of the second decade of life
* secondary embryonic cartilage
Coronoid cartilage appears where? does what?
1) appears at 4 months in utera and surmounts the anterior border and top of the coronoid process
2) a transient cartilage center that disapears before birth
* secondary embryonic cartilage
what is Symphyseal cartilage?
- appear in and are independent of MC
- two in number
- last within one year of birth
- transient structure in the developing alveolar processes
- secondary embryonic cartilage
where do alveolar plates develop?
above the bony canal; Odontogenic epithelium forming the tooth germs lies superiorly
describe the growth of the tooth germs?
what does the groove include?
1)bone of mandible grows on each side
*2)causes tooth germs to be in a groove
(groove includes alveolar nerves and vessels)
3) septa grows bw the germs to keep each separate
4) alveolar processes grow at a rapid rate during periods of tooth eruption
The ramus of the mandible develops by a rapid spread of ossification backwards into the mesenchyme of the? this diveragance is maked by?
first branchial arch diverging away from Meckel’s cartilage
**point of divergence is marked by the mandibular foramen
what is MdPGC?
mandibular primary growth center
- detectednear the apical area decidious molar tooth germ
- linear trabeculae extend towards coronoid process
what type of joint is TMJ?
synovial sliding-ginglymoid joint (aka modified hinge type of synovial joint)
TMJ movements
elevation depression retraction protraction side to side
TMJ articulation
1 condyle of the mandible
2 articular tubercle and mandibular fossa
capsule of TMJ attaches to?
temporal bone and around neck of mandible
articular surface of TMJ are covered by?
**MAKES TMJ UNIQUE
fibrocartilage! *NOT hyaline
articular disc of TMJ divides joint space into two compartments ?
1) lower compartment= hinge movement to depress and elevate
2) upper compartment= protrusion and retraction movement
what are the 5 zones of epiphyseal plate growth for long bones?
1) resting/reserve zone
- – hyaline cartilage, inactive
2) proliferation
- –chondroblasts rapidly divide
- – push epiphysis away from diaphysis as it makes rows
3) hypertrophic zone
- –bigger in size, not in number
- –Alkaline phosphodiase causes CALCIFICATION
4) calcification zone
- –THIS IS NOT BONE
- –osteoclast degrade hyalin cartilage
5) ossification zone
- –lacuna wall breakdown by osteoclasts
- –osteoblast replace with actal bone
how is condylar secondary cartilage different from primary?
*which reason is an biomechanical adaptation?
1) it is heterogenous containing fibroblasts, osteaochondral progenitor cells and chondrocytes
2) Type 1 and 2 collagens are co-localized in cartilaginous cell layer
* *Co-localization of both collagen types is an biomechanical adaptation
peripheral condylar cartilage contains?
chondroid bone, a specialized calcified tissue intermediate between those of bone and cartilage
long bones typically have articular cartilage for shock absorbance and a gorwth plate, what is unique about the mandibular condylar cartilage?
It is a SINGLE cartilage
- ‘‘all-in-one type tissue’’.
- plays roles in articulating function and growth
- exists in the mandible throughout life
each condyle of the TMJ consists of compact bone with overlying ____ bone?
cancellous
what covers the periosteum?
ribrocartilage
the growth centers consists of hyaline cartilage underneath the? WHAT IS UNIQUE ABOUT IT?
periosteum on the articulating surface of the condyle.
*LAST growth center of bone in the body and MULTI DIRECTIONAL in its growth capacity (unlike a typical long bone)
