mandible and TMJ Flashcards
meckel’s cartilage
in each mandibular process of BA 1
what are the roles of meckel’s cartilage
- temp skeleton of man. processes of BA 1
- temp attachment for mm that eventually attach to the mandible
- cartilage models/OSSIFICATION CENTERS for the malleus and incus
- appearance site of 2 ligaments (anterior mallelar and sphenomandibular)
- temp anterior lingual plate of forming mandible halves
- serve as enclosed GROWTH SITES at the chin end of the mandible
fate of meckels cartilage
- endochondral ossification centers for the 2 ossicles
- retrogressive changes to become the 2 ligaments
- undergo growth, mineralization and resorption while serving as an ANTERIOR GROWTH SITE and replaced as temporary anterior lingual plate by the encroaching bone tissue of the growing mandible halve
what is an ossification center
initial appearances of bone tissue in the area where each of the bone organs of the body form
where can ossification centers appear
- w/in mesenchyme
2. on or w/in cartilage model
if ossification centers appear w/in mesenchyme it is called
intramembranous bone organ development
if ossification centers appear on or w/in a cartilage model it is called
endochondral bone organ development
do the # of ossification centers vary from bone to bone
yes
how many o.cs does the mandible have
1 for each half
how many o.cs does the maxilla have
2 in each bone…so 4
mandible and maxilla development are examples of
intramembranous ossification
what are growth sites
addition of bone tissue to a bone organ
intramembranous bone tissue
bone tissue always forms in a highly vascular c.t called intramembranous bone tissue
the PDL is a
growth site
when does the mandible begin development
6th embryonic week
where does the mandible arise from
from 2 bilateral ossification centers within mesenchymal tissue (intramembranous) lateral to meckel’s
where do the ossification centers appear
in the area where the inferior alveolar nerve branches into the mental and incisive nerves (future mental foramina)
bone tissue grows
anterior to posterior from the center
how does the anterior mandible grow
the bone incorporates the distal parts (chin) of meckel’s cartilage
the incorporated part of each cartilage becomes
the temp lingual plate and a GROWTH SITE of each mandible half
how does the posterior mandible grow
the posterior end of the facial plate incorporates an independent piece of hyaline cartilage
the hyaline cartilage incorporated by the posterior mandible becomes
the condylar cartilage which is a GROWTH SITE of each mandible half
does the condylar cartilage arise from meckel’s cartilage
no
when does osseous union occur
first postnatal year
proximal end of MC serves as a model for
malleus and incus and anterior mallelar ligament
the middle area of MC serves as a model for
sphenomandibular ligament
the distal end of MC serves as a model for
temp anterior lingual plate and growth site of growing mandibular halves
the mylohyoid is attached to the
medial sides of MC
malleus and incus form via
endochondral ossification
what type of joint is a tooth in a bone socket
gomphosis
what type of joint is the maxilla
synarthrosis…little or no mobility
what type of joint is the TMJ
diarthrosis..freely moveable
what 2 bones make up the TMJ
- squamous portion of the temporal bone
2. condyloid process of the mandible
unique features of the TMJ
- complete articular disk
- joint cavities
- soft c.t articulating surfaces
TMJ starts formation with the appearance of a
blastema…site of condylar cartilate appearance and the articular disc
when does the blastema appear
8 week embryo
when does cavitation of the blastema occurs in the embryo for the TMJ
3rd month in utero
how long does the condylar cartilage remain
age 25
what is a blastema
rudimentary substance from which cells, tissues, organs are formed
what forms from the TMJ blastema
joint cavities (2)..condylar cartilage, articular disc, soft tissue articular surfaces
