mandible and TMJ 2

Question 1

cells in the proximal part of the mandible have the potential to become either? and are therefore called?

Answer 1

osteoblasts or chondrocytes

*they are called osteochondroprogenitor cells

Question 2

mandible growth until birth is influenced by the appearance of 3 secondary cartilages?
*called secondary why?

Answer 2

(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

Question 3

secondary cartilages develop as a result of what?

Answer 3

stresses and strains in the intramembranous bone, NOT by interactions with epithelium

Question 4

Like many cephalic cartilages, secondary cartilages develop from?

Answer 4

mesenchyme of ectodermal origin (neural crest)

Question 5

what secondary cartilage is carrot shaped?

Answer 5

condylar

Question 6

condylar cartilage is what part of mand?
type of ossification?
remant?

Answer 6

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

Question 7

Coronoid cartilage appears where? does what?

Answer 7

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

Question 8

what is Symphyseal cartilage?

Answer 8

• 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

Question 9

where do alveolar plates develop?

Answer 9

above the bony canal; Odontogenic epithelium forming the tooth germs lies superiorly

Question 10

describe the growth of the tooth germs?

what does the groove include?

Answer 10

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

Question 11

The ramus of the mandible develops by a rapid spread of ossification backwards into the mesenchyme of the? this diveragance is maked by?

Answer 11

first branchial arch diverging away from Meckel’s cartilage

**point of divergence is marked by the mandibular foramen

Question 12

what is MdPGC?

Answer 12

mandibular primary growth center

• detectednear the apical area decidious molar tooth germ
• linear trabeculae extend towards coronoid process

Question 13

what type of joint is TMJ?

Answer 13

synovial sliding-ginglymoid joint (aka modified hinge type of synovial joint)

Question 14

TMJ movements

Answer 14

elevation
depression
retraction
protraction
side to side

Question 15

TMJ articulation

Answer 15

1 condyle of the mandible

2 articular tubercle and mandibular fossa

Question 16

capsule of TMJ attaches to?

Answer 16

temporal bone and around neck of mandible

Question 17

articular surface of TMJ are covered by?

**MAKES TMJ UNIQUE

Answer 17

fibrocartilage! *NOT hyaline

Question 18

articular disc of TMJ divides joint space into two compartments ?

Answer 18

1) lower compartment= hinge movement to depress and elevate

2) upper compartment= protrusion and retraction movement

Question 19

what are the 5 zones of epiphyseal plate growth for long bones?

Answer 19

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

Question 20

how is condylar secondary cartilage different from primary?

*which reason is an biomechanical adaptation?

Answer 20

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

Question 21

peripheral condylar cartilage contains?

Answer 21

chondroid bone, a specialized calcified tissue intermediate between those of bone and cartilage

Question 22

long bones typically have articular cartilage for shock absorbance and a gorwth plate, what is unique about the mandibular condylar cartilage?

Answer 22

It is a SINGLE cartilage

• ‘‘all-in-one type tissue’’.
• plays roles in articulating function and growth
• exists in the mandible throughout life

Question 23

each condyle of the TMJ consists of compact bone with overlying ____ bone?

Answer 23

cancellous

Question 24

what covers the periosteum?

Answer 24

ribrocartilage

Question 25

the growth centers consists of hyaline cartilage underneath the? WHAT IS UNIQUE ABOUT IT?

Answer 25

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)