Orofacial Development: Mandible and TMJ Flashcards
mandibular process is what part of 1st PA
lower part
what does mandibular process differentiate into
soft tissue, cartilage and bone
what is a primary cartilage that develops early from hyaline
Meckel’s cartilage
what iis the developmental precursor for middle ear bones (malleus/incus) and provides scaffold for mandible to develop around
Meckel’s cartilage
secondary cartilages help wiith growth of what
mandible
types of secondary growth cartilage
condylar, angular, coronoid, and symphyseal
external permanent structures of mandibular process
- chin
- lower lip and commissure (formed by fusion of max and mand process)
internal permanent structures of mandibular processs
- mandible
- condyle of mandible/TMJ
- mucosa of anteriior 2/3 tongue
- middle ear bones (malleus and incus)
what develops from derivatives of Meckels’ cartilage (2 middle ear bones)
Primary (temporary) TMJ joint
what develops from squamous portion of temporal bone and condylar head of mandible (both PA1)
secondary (permanent) TMJ joint
___ and ___ appear as two distinct regions of ectomesenchyme of first arch during development
temporal bone and condyle
___ is a primary cartilage that extends as rod of hyaline cartilage from ear to midline of mandibular process (not fused in midline)
meckels
steps of primary TMJ development
- Meckel’s cartilage differentiates from ectomesenchyme of mand 1st PA
- differentiation of Meckel’s cartilage
- posterior region of meckel’s ossifies
- formation of temporary (primary) TMJ
- malleus and incus become incorporated into middle earcavity
what stage do incus and malleus form
stage 3
what stage do malleus and incus artiiculate an dmove
stage 4
adult derivative and function of the following Meckel’s cartilage region:
posterior region
AD: malleus, incus, anterior ligament of malleuss
function: malleus and incus 1st PA articulate with stapes middle ear bone 2nd PAL
anterior ligament attenuatess movement of malleus
adult derivative and function of the following Meckel’s cartilage region:
middle region
AD: sphenomandibular ligament
function: limits inferior displacement of mandible; passive support to TMJ
adult derivative and function of the following Meckel’s cartilage region:
anterior regiion
AD: degenerates eventually
function: signaling center - stimulates development of symphyseal cartilage (secondary growth cartilage)
what contributes to 2 middle ear bones and 2 ligaments
meckels
does meckels contribute to mandible
NOOO
secondary/permanent TMJ develops from what
PA1st mandibular and PA1st maxillary
what structures of TMJ are 1st PA derivatives and received innervation from CN V
ALL STRUCTURES
___ and ___ develop as secondary growth cartilage
condyle and articular eminince
the ___ stays as fibrocartilage until 20 yrs and is a significcant source of mandibular growth
condyle
bone remodeling of adult mandible occurs in response to what
mechanical load
___ is associated with condylar head and artiicular eminence to facilitate remodeling
fiibrocartilage
is there hyaline in the TMJ
NOOOO
what are TMJ arttiicular joint surfaces covered with? why?
perichondrium (DRCT) - DRCT allows for repair and strimulates remodeling in response to occlusal loads
what type of cartilaginous growth occurs in TMJ
apposititonal due to perichondrium
articular disc is comprised of what CT
fibrous CT (DRCT)
what is divided into thick, peripheral anterior and posterior bands
articular disc
what is thin, avascular, and lacks innervation in articular disc
central intermediate zone
sensory receptors are found where in regards to disc
joint capsule, ligaments, retrodiscal pad, periphery of disc, and lateral pterygoid muscle
what type of innervation to capsule to provide feedback about joint poisition and masticatory force
proprioceptive innervation
what type of innervation in capsule to alert to trauma
sensory pain receptors and fibers
when does mandible develop LATERAL to meckel’s
step 3 - maturation stage
how does mandible ossify
- endochondral (condyle)
- intramembranous (body and ramus)
primary ossification site of mandibular body begins where
bifurcation of inferior alveolar nerve into incisive and metnal branches
ossification of body and ramus occurs where compared to the points of initial ossification
POSTERIORLY
what nerve do we find when given a histo slide of the mandible
inferior alveolar nerve
what cartilages are transient, forming in association w/ only bones that develop by intramembranous ossificccation
secondary growth cartilage
what develops after ossification begins and aid in the growth of intramembranosu bones
secondary growth cartilage
