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
When do primary and secondary ossification centers complete?
primary end at age 6
Secondary at age 25
Where are the primary ossification centers ? when do they start and end?
secondary ossification centers?
1 body 2 in forming arches 7weeks to 6 years old
secondary are on periphery of bodies and ends of processes and last till about 25yo.
What parts of the vertebral column are bony at birth?
two Half -arches and the centrum (forms body)
What forms the nucleus pulposus and the anulus fibrosis?
Notochord forms nucleus pulposus
Mesenchyme forms anulus fibrosus
Where are the intervertebral discs formed from
Notochord and mesenchyme of somites
The vertebral body is made from what neurological layer?
Describe the development of the notochord
Sclerotome.
Most of the notochord degenerates but the parts between the vertebral bodies end up forming the Nucleus pulposus
Resegmentation occurs as each vertebra forms from the fusion of the caudal half of the sclerotome of one somite and the cranial half of the subjacent somite.
How many cervical somites do we have? why do we have 7 vertebrae?
We have 8 cervical somites (each with its own innervation),
The caudal half of O4 and the Cranial half of C1 forms the base of the occipital bone.
The caudal half of C8 and cranial half of T1 forms the T1 vertebrae. This is why we only have 7 cervical vertebrae
Visceral mesoderm is initially between somites and finish at mid-vertebrae— these are called?
Intersegmental arteries (Visceral lateral plate mesoderm)
outgrowth of neural tube initially at mid-somite level finishes between vertebrae. These represent the?
Spinal nerves (Neural tube- neuro ectoderm)
Why do spinal nerves innervate multiple muscles?
Because Most muscles derived from multiple segments
Myotomes undergo resegmentation end up spanning two segments of the vertebral column. What muscles are these?
Rotatores brevis (myoblast from a single myotome)
Ribs and sternum are derived from two different layers?
Ribs- Sclerotome (just like vertebrae)
Sternum- Lateral plate - parietal layer (b/c part of body wall)
What is it called if the left and right halves of the sternum don’t fuse appropriately?
Cleft Sternum
LOF mutations of HOX9 results in? rodents*
rib cages with 13 ribs attached to sternum
LOF Hox9 produces
floating ribs
Hox inhibition where its usually expressed leads to
LOF
Hox expressed where its usually not
GOF
If T1-t10 had a GOF of hox9 what would be seen?
No ribs attached to sternum
Hox10 prevents rib formation- so a GOF/LOF
GOF Hox10 has no ribs
LOF hox10 has all ribs
HOX11 fuses vertebrae– sacrum
sometimes 6 fused , othertimes 4 fused. what is that called respectively?
Sacralization of L5 vertebra- Hox11 GOF at L5
Lumbarization of S1 vertebra- Hox11 LOF at S1
What is it called when a vertebra doesnt form completely?
Hemivertebra
Fracture of vertebral arch called
spondylolysis
Dislocation between adjacent vertebrae subsequent to sondylolysis
Spondylosisthesis (congenital developmental defects or trauma)
When one or more vertebral arches fail to develop or fuse
What called if no herniation of meninges or spinal cord?
What called if herniation of meninges/spinal cord?
Spinabifida (caudal neuropore failure)
_spinabifida occulta- no herniation
Spinabifida cystica
Severe caudal failure, in which neural tissue is exposed and often becomes necrotic
Rachischisis (ra kis chi sis)
What can indicate a neural tube defect?
Alpha fetoprotein increase in maternal serum or amniotic fluid (need Folic acid before pregnancy)
2,3,4,5,6,8 weeks of development
2- uteroplacental exchange & bilaminar disc,
3, Gastrulation, nurulation, body folding
4. limb buds,
5. resegmentation of somites into vertebral bodies
6. chondrification centers form in vertebra
7-8. Primary ossification centers form- fingers developed
