Embryology of the Pharyngeal Arches Flashcards
Pharyngeal Arches Components
ectoderm, mesoderm/neural crest, endoderm, nerves, CN associated w/ arch.
lingual swellings
hypobranchial eminence
-what week do the arches form
Ectoderm: groove (cleft), and covering
Mesoderm/Neural Crest: mesoderm gives rise to muscle and the aortic arch, neural crest gives rise to skeletal
Endoderm: lining on 2,3,4,6 but maybe not 1. pouches for each arch
Nerves are sensory and motor: mixed
Arch one is CNV, arch two is CN 7, arch three CN 9, arch four/six are CN 10
lingual swellings give rise to tongue
eminence gives rise to epiglottis
form during week 4
1st Arch Ectodermal derivatives
- Cleft gives rise to?
- Covering gives rise to?
stomodeum is mouth
anterior pituitary rathkes pouch
ear comes from arch 1 and 2
Ectoderm derivatives
what does arch 2 normally do?
grows down over arches 3 and 4 and should fuse and fill area with tissue completely. sometimes you get a lateral cervical sinus or a cyst
Brancial Cyst
- how, remnants of what?
- usually develop where?
sinus vs cyst
cyst is a fluid filled pouch, a sinus has one opening
Neural crest
- migratory patterns
- give rise to
give rise to cartilage and bone
Neurocristopathies
Mesenchyme derivatives of the arches:
meckel cartilage turns into mandible so from first arch NCC
sphenomandibular ligament and ossicles of ear come from NCC
second arch gives off reichert cartilage: gives rise to styloid process, styloid ligament, lesser cornu/ upper body of hyoid, and the stapes of the ear
3rd arch: greater cornu and lower body of hyoid
4/6 thyroid cartilage and larynx
Mesoderm
- where do muscles come from
- each arch gives rise to which muscles
muscles come from paraxial mesoderm
where do eye muscles come from? innervation
where do tongue muscles come from? innervation
prechordal plate mesoderm CN 3,4,6
tongue are occipital myoterms CN 12
Endoderm derived arch stuff: arch 1,2,3,4
- pouches of each arch
- where do tonsils come from
- what is ultimobranchial body
tonsils are mesoderm but the palatine fossa it lies in is endoderm
ultimobranchial body gives rise to signals to recruit NCCs to make C cells, which secrete calcitonin
What happens to pouch 3 and 4
Thyroid:
develops when?
where does it come from?
comes from oral cavity between arch 1/2, decends through foramen cecum and thyroglossal duct
develops on day 24
-thyroid primordium from endoderm of pharynx, descends in neck anterior to hyoid and laryngeal cartilages.
adult position by 7th week
Thyroglossal duct cysts and sinuses
sinus on left, cyst on right figure
- if cyst becomes infected it become an opening
- lateral branchial cysts are usually detected by age 5 whereas thyroglossal cysts are later childhood early adulthood.
Ectopic thyroid:
- places of ectopicsy
- pyramidal lobe is remnant of?
pyramidal remnant of thyroid
First Arch Syndrome:
symptoms
why
2 main types
abnormal ear, jaw, cleft palate, eye formation
abnormal NCC migration
Treacher Collins Syndrome, Pierre Robin Sequence
Treacher Collins Syndrome:
- inheritance
- which gene, what does it do
- characteristics
brain development fine
Pieree robin sequence:
-inheritance
DiGeorge Syndrome:
- failure of what to form? which pouches are responsible?
- characteristics?
- what chromosome gene deletion
pouches 3/4
NCC migration causes mouth abnormalities, ears, nasas clefts
q11.2 on chromosome 22
Pharyngeal Pouch Derivatives:
palatine fossa for whited out part
How are arch structures innervated for sensory?
-sensory branch goes to arch above it and innervates it. “pretrematic division”
summary of arches and their derivatives
**know the adult derivatives, arch number, CN, muscles, skeletal are coming from NCC, and then know the endodermal pouch**
Arch Sensory vs Mixed chart
