Development of the Mandible & Tongue Flashcards
whats the mandibular process
developmental structure
lower1/3 face early dev
gives rise to mandible chin, lower lip
what is the mandible
bone
lower jaw
what is PA 1 imp for dev
mandible
mandibular arch
what is PA 1, 2 and 3 imp for dev
tongue
what is PA 4 imp for dev
4 thyroid gland
what does PA 1 do
lay framework for dev of mandible through meckels cart
malleus and incus
what re the muscles asscw with PA 1
muscle mast ABD mylohyoid tensor tympani tensor veli palatini
what is cart
sting flexible semi rigid support tissue
what can act withstand
compression forces and yet can bend
what is cart made by
chondroblasts and chondrocytes
what is the ecm of cart made of
10% aggrecan
75% water
mx collage fibres
what are the type of cart
hyaline
fibrocart
elastic
what is hyaline
most common
glassy appearance
what is fibrocart
tension insertions
intervertebral discs
reinforced with collagen bundles stop bones rubbing
what is elastic cart
eternal ear and epiglottis
flexible and resilient
elastic fibres
what is cart for
framework support - airways
articulating surfaces of bones
template for growth and dev long bones
what are the cells of cartr
chondrblast
chondrocyte
how do chondorblasts make cart
ECM sec by chondroblasts
trapped - chondrocytes form nests 2-4
lacunae
what si the surface of most cart
dense irregular CT - perichondrium
what id the outer layer of the crat
lots collagen prod fibroblasts and inner layer chondroblasts
how is crd unlike other CT
avascular so doesn’t gain any extra nutrients etc
what are the two growth mechanisms used for cart growth
interstitial growth
appositional growth
what is interstitial growth
chondrocytes grow and divide lay down more matrix inside the existing cart dev
what is appositional growth
new surface layers of matrix are added to pre existing matrix by chondroblasts from perichondrium
where does meckels cart form
in mand under tongue comes around doesnt meet in midline
what is meckels cart
cart of 1st arch
for mandible
6th week dev
from otic capsule to midline symphysis
by week 10 what has happened to meckels crat
mand formed bone used mocked cart template
what comes from the posterior extremity of meckels cart
malleus and sphenomalleolar ligament
what comes from the the sphenoid to div of mand nerve of meckels cart
cart disappears
its fibrocellular capsule persists as spehnomandibuar ligament
what comes from the lingual forward to div of alv nerve of meckels
totally absorbed
what comes from meckels cart froward to midline
makes contribution to mandible by endochondral osification
what is CCN2 required for
or CT GF required for proper dev of orofacial region
mandibular morphogen
what does CCN2 accelrate
adhesion and aggregation 1st arch cells
promote remodel
what ossify for mand
intraemmbranous ossification
where si the primary centre of ossification for mand
between incisive and mental nerve
what are the growth factors involved in for of mandible
vascular endothelial GF (VEGF)
transforming GF beta 1 and some BMP’s
what ossification takes place at secondary cartilage sites
endochondral
what is osteogenesis
process of laying down new bone material by osteoblasts
what does mand endochondral ossification
for fo condensed mesenchyme chondrocytes dev = cartilaginous element
what are th mandibular secondary cartilages
coronoid cart
symphyseal cart
condylar cart
when dos the condylar car appear and diaspeae
appear - 10-12 weeks
disappear at 20 y.o
when does the coronoid cart appear and disappear
appear - 14-16 weeks
disappear before birth
when does symphyseal cart appear and disappear
appear - 16 weeks
disappear 1st year after birth
how do secondary carts differ from primary
not part primary skeleton
fibrocart stop rubbing
appositional growth not interstitial
what does the endochondral ossify of secondary carts mean
surface depo of new cart
calcification of sub-surface cart
resorption of calcified tissue
replace calcified cart w bone
what are some dev abnormalities of mandible
agnathia
micrognathia
maccrognathia
what is agnathia
no mandible
lack ectomesenchyme in mand arch
fatal
what is micrognathia
v small mand
lack ectomesenchyme in arch
downs syndrome
what is macrognathia
v large mandible
genetic
pituitary disordes - acromegaly
what does the 3rd arch form
greater horn of hyoid inf hyoid bone root tongue stylopharygeus nerve IX
when does the formation of tongue begin
week 4
what does formation of tongue involve
PA 1
PA 3
PA 4
occipital somites
what does PA 1 do in tongue form
2 lingual swellings laterally
tuberculum impar
what does pA 3 do in tongue form
hypobranchial eminence
what makes muscles assc with tongue
PA 4
occipital somites
what does the foramen caecum form
thyroid gland form
what is diff of sulcus terminals
diff epi
how is there detachment of tongue ant 2/3
ectoderm grows between ant 2/3 and underlying arch
degenerates except in midline frenulum
what makes ant 2/3 lingual mucosa
PA 1
general sense - trigem
taste - chords tymp facial
what makes post 1/3 lingual mucosa
PA 3
inn glossopahrygeal
what is origin of palatoglossu
PA 4
inn - phargeal plexus vagus
what forms other intrinsic and extrinsic muscles of tongue
migration of occipital somites
inv - hypoglossal
what is the abnormal failure to fuse
bifid tongue - forked - triffid
what is imperfect detachment of tongue
ankyloglossia
tongue tie
what are some growth disorders assc with tongue
aglossia - arare
microglossia - cleft palate
macroglossia - downs
what is PA 2 called
hyoid arch
what is cart of PA 2
reicharts acrt
what does PA 2 from
stapes
lesser horn and sup hyoid body
styloid process
stylohyoid ligament
what are the muscles assc with PA 2
facila esp and PBD
what gland assc with PA 2
thyroid gland nd tonsil
what is de of thyroid gland assc with
tongue dev
how si thyroid gland grown
epithelial down growth from foramen caecum
migration down midline to thyroid
disintegration fo thyroid duct
what are some abdnoamltitis with thyroid dev
ectopic thyroid gland
tissue left behind
thyroglossal duct persist
