B7.036 Embryology of Head and Neck Structures Flashcards
components of the branchial apparatus
branchial clefts
branchial pouches
branchial arches
branchial clefts
ectodermal ingrowths
branchial pouches
endodermal outpocketings
branchial arches
mesenchymal core (mesoderm and neural crest) in between the clefts and the pouches
how are cranial neural crest cells formed
derived from dorsal neural ectoderm
cells delaminate by epithelial mesenchymal transition and migrate rostrally over neural tube to form branchial arches
function of neural crest cells
migrate throughout the embryo and give rise to many different adult cells
give rise to majority of craniofacial structures
first arch syndromes (neurocristopathies)
congenital malformations result from mutations in genes that play a role in neural crest function (induction, proliferation, EMT, migration)
examples of first arch syndromes
syndromic phenotypes that include craniofacial abnormalities:
- branchiooculofacial syndrome: AP2
- campomelic dysplasia: SOX9
- mowat-wilson syndrome: ZEB2
- DiGeorge syndrome: TBX1
- treacher-collins syndrome: treacle
- saethre-chotzen syndrome: twist
DiGeorge mnemonic
CATCH 22 cardiac abnormality abnormal facies thymic aplasia clef palate hypocalcemia/ hypoparathyroidism deletion on chromosome 22
constituents of the branchial arch
artery (aortic arch)
nerve (CN): V, VII, IX, X
muscle (from mesoderm)
cartilage (from neural crest)
pharyngeal cleft
invagination of the ectodermal layer
pharyngeal pouch
outpouching of the endodermal layer
how are arches, clefts, and pouches arranges
arch is above the same numbered cleft / pouch
clefts and pouches are in line with one another
1st and 2nd aortic arches
degenerate
3rd aortic arch
passes through 3rd pharyngeal arch and persists as the stem of the internal carotid artery (and part of the common carotid)
4th aortic arch
persists on the right as the subclavian artery
on the left becomes a portion of the arch of the aorta
6th aortic arch
survives as the pulmonary arteries and ductus arteriosus
defects in great arteries
usually due to persistence of arches that should have degenerated
innervation of branchial arch 1
trigeminal CN V
innervation of branchial arch 2
facial CN VII
innervation of branchial arch 3
glossopharyngeal CN IX
innervation of branchial arches 4-6
vagus CN X
first arch muscles
mastication
-temporalis
-masseter
anterior belly of digastric
second arch muscles
facial expression
posterior belly of digastric