Pharyngeal (Brachial) Arches Flashcards
what does ectoderm give rise to
skin and neural tube
what does ectoderm come from
form epiblast layer
what does mesoderm layer give rise to
just about everything else
where does mesoderm come from
migratory cells of epiblast layer
what does endoderm give rise to
gut
what does endoderm come form
from hypoblast layer
what sit he neural crest / ecto-mesenchyme come from
from ectoderm that migrates into mesoderm to form structures of head and neck
what is the opening for the mouth called
stomatodeum
how long until PA form
20 days
what does the PA give rise to
most head and neck region
when is all head and neck prod
56 days
very rapid dev
at 28 days what can be seen structure of embryo
fronto-nasal prominence
stomatodeum
PA
cardiac swelling
what can be seen on frontonasal prominence
lens placode
when do PA appear
4th - 5th week
what is the PA
bars of ecto-mesenchymal tissue migrate in
what are the arches sep by
clefts/grooves - externally and pouched internally
whtare th genes of the PA that control dev
hoxabox genes
which allow cells to differentiate correctly
what are the PA branches numbered
1 2 3 4 6
why is there no PA 5
doesn’t exist in humans
sometimes appears as swelling but dissaears
what does a PA consist of
ectoderm - outside endoderm - inside except PA 1 cartilage blood vessels and nerve muscle
what is the 1st arch
mandibular arch
what des the mand arch give rise to
mandible and max processes body tongue muscle mast Trigeminal max and carotid A's
what is the cartilage in the 1st arch
meckels cart
what is meckels cart
primitive support
largely disappears
what does merckels cart form
2 bones - incus and malleus
2 ligaments - sphenomand, sphenomalleolar
what is the mutation of PA 1
teacher collins syndrome
what causes teacher collins syndrome
can be single polymorphism
neural crest doesn’t form properly so abnormal form and and zygoma
what happens in teacher collins
fail neural crest migration facial bone hypoplasia ear abnormalities clefts dental anomalies
what are some dental anomalies that can occur in teacher collins syndrome
tooth agencies
enamel deformitits
misplacement upper 6’s
what is the 2nd arch
hyoid arch
what si the crat of PA 22
Reicharts cart
what does reicharts arch form
stapes
lesser horn and sup hyoid body
styloid process
stylohyoid ligament
what else is present from the PA 2
facial expression muscles PBD thyroid gland tonsil facial nerve
what doe the PA 3 form
greater horn hyoid inf hyoid body root tongue stylopharyngeus glossopharyngeal
what does PA 4 form
thyroid cart pharynx epiglottis pharyngeal constrictor soft palate vagus - sup laryngeal nerve
what does PA 6 form
cricoid and arytenoid cart
larynx
muscles larynx
vagus - inf laryngeal
what does the 1st groove form
EAM and ear drum
what happens to the 2nd - 6th clefts
disappear
obliterated by proliferating 2nd arch
what des the 1st pouch form
eustachian tube
middle ear cav
tymp mem
ventral part obliterate by tongue
what does the 2nd pouch form
tonsillar fossa
ventral part obliterated by tongue
what does 3rd pouch form
inf parathyroid gland nd thymus
what does 4th pouch form
sup parathyroid gland
what is formed with the remnants of the 2nd-4th clefts
cervicalsinus
where are pharyngeal membranes found
in the floor of the pharyngeal grooves
where do the pharyngeal mems form
where epi of grooves and pouches approach each other
what separates the endoderm and ectoderm
mesenchyme
what PA mem become
tymp mem others obliterate
what is brachial fistula/cyst
2nd arch fails to grow down sufficiently over 2nd and 4th clefts
along ant border of SCM
what is ectopic thyme or parathyroid tissue
failure to migrate completely
