L21-22: Pharynx, Digestive System, Respiratory System Flashcards
pharyngeal arch structure
mesenchyme core
covered by ectoderm
inside lined w/ endoderm
separated from each other by grooves
components:
artery/aortic arch
cranial nerve
skeletal component
pharyngeal endoderm uses Tbx1 to ?
cause expression of FGF8 to induce pharyngeal arch formation
what is the only muscle derived from pharyngeal arch 3
stylopharyngeus muscle
1st pharyngeal arch
mandibular arch
trigeminal CN V
derivatives:
–meckel’s cartilage
2nd pharyngeal arch
hyoid arch facial CN VII derivatives: --reichert's cartilage (hyoid, stapes, styloid process) --muscles of facial expression
hoxa2 required for arch development
3rd and 4th pharyngeal arches
glossopharyngeal CN IX vagus CN X derivatives: --part of hyoid, upper pharynx --stylopharyngeus muscle --4th: muscles/cartilages of larynx and lower pharynx
derivatives of pharyngeal grooves
external auditory meatus – 1st groove
cervical sinus – 2nd/3rd grooves
**this is a temporary structure
pharyngeal pouch derivatives
1st
tympanic cavity, auditory tube
2nd
fossa for tonsils
3rd
inferior parathyroids (shh)
thymus (BMP4)
4th
superior parathyroids
beginning of thyroid development
- begins as node of cells btwn 1st/2nd pharyngeal arches
- induced via signals from underlying mesenchyme
- thyroid cells express:
hhex, nkx2-1, pax8, foxe1
define foramen cecum
the thyroglossal duct connects the thyroid diverticulum to the pharynx
the opening of this duct persists as a small pit at the base of the tongue = foramen cecum
lateral lingual swellings
located in ventral parts of 1st arch
tuberculum impar
ventral swelling btwn 1st/2nd arches
copula
ventral swelling btwn 3nd/4rd arches
**foramen cecum is located btwn tuberculum impar and copula
patterning of ant/post domains of the gut
ant = nodal post = FGF4 w/ strong expression near the foregut/midgut boundary
how do the following factors effect the foregut or hindgut?
cdx2
pdx1
FGF10
2 — hox gene expression in mid and hindgut
1 — sets apart midgut
10 — establishes cecum
stages in development of esophagus
- circular layer of sm
- longitudinal layer of sm
- stratified columnar epi
- large vacuoles appear
- lumen recanalizes
- ciliated columnar epi
- epi replaced w/ stratified squamous epi
sm derived from splanchnic mesoderm
skeletal muscles derived from paraxial mesoderm
initial induction of gut endoderm to form liver
septum transversum — BMP
cardiac mesoderm — FGF
transition from simple cuboidal to pseudostratified columnar in liver formation requires ?
Hhex activity
formation of hepatic cords
requires loss of E-cadherins and proliferation of cells Hhex prox1 tbx3 HNF6
bipotential of hepatoblasts
they can become
hepatocytes or
cholangiocytes
pancreas arises from 2 primordia
dorsal pancreas:
dorsal gut endoderm
ventral pancreas:
depends on Ptf-1a activity
initial site for the development of the respiratory system
the floor of the pharynx/ventral foregut
site is marked by TF nkx2.1
the respiratory bud is primordium for the trachea
what arches are the superior laryngeal and recurrent laryngeal nerves associated w/?
sup – 4th arch
recurrent – 6th arch
formation of the bronchial tree
pair of buds form at distal end of tracheal bud = bronchial bud
this forms the primary bronchi
and the primary buds give off additional buds to form the rest of the tree
