EXAM3_19_Trunk_Development Flashcards
What expression at the primitive node initiates/maintains the primitive streak?
Nodal TGF-B Family expression
What expression controls cell migration and invagination?
FGF8 expression
What is spemann’s organizer?
Primitive node
Somitomeres form on sides of cranial neural tube and differentiate into what?
Most skeletal muscles of the head
Somites form on the sides of notochord and neural tube and differentiate into what?
skeletal muscles Axial skeleton
What drives somite identification?
HOX expression
What gradient drives differentiation of cranial to caudal? and what does that promote?
Retinoic Acid — promotes HOX expression to drive somite identification
All skeletal muscle is derived from Paraxial mesoderm somites and somitomeres at the same time as what?
at the same time neurulation occurs in ectoderm
SHH is involved as ectoderm forms neuroectoderm (forming neural tube and neural crest). What does SHH and BMP4 then induce?
SHH induces anterior neural tube (motor)
BMP4 induces posterior neural tube (sensory)
What two expressions induce sclerotome development?
SHH (from neural tube) and Noggin (from notochord)
What expression induces dermatome development?
NT-3
What expressions induce myotome development?
WNT + (SHH or BMP4)
Sclerotome cells express what?
PAX1
Dermatome cells express what?
PAX 3
Myotome cells express what?
MyoD (hypaxial) or Myf5 (epaxial)
these divisions form by week 5
Myotome differentiation caused by MYF5 expression are what type of muscles? what is significant about their myoblast differentiation?
Epaxial (intrinsic) muscles, the myoblasts don’t migrate
Some myoblasts of hypaxial derivatives do not migrate (just like epaxial myoblasts), what is an example of hypaxial myoblasts that do not migrate?
Intercostal Muscles, Abdominal muscles
upper limb muscles DO migrate
In utero ossification begins at ___ weeks?
7 weeks