Limb development Flashcards
When does limb development occur?
4-8 weeks
When are limb buds visible?
4 weeks
What are limb buds visible as at end of week 4?
Outpouchings from the ventrolateral body wall
What does the limb bud consist of at first?
Core tissue derived from lateral plate mesoderm
The plate mesoderm is covered in what?
Ectoderm
The mesoderm core differentiates into what?
Mesenchyme which = connective tissue and bones
Skeletal muscle comes from where?
Paraxial mesoderm
What does the paraxial mesoderm differentiate into?
Somites
The somites differentiate into a ventral what?
Sclerotome
Sclerotome forms what
vertebral column
What does the dorsolateral part of the somit form?
Dermomyotome = dermatome and myotome
What does the dermo and myotome give rise to?
Skin and muscle
Myotome differentiates into two parts?
Dorsal epimere, ventral Hypomere
Epimere forms what?
Back muscles dorsal rami
Hypomere forms what?
Thoracic and abdo muscles with ventral
Where does limb muscle come from?
Hypomere region adjacent to upper and lower limb buds
Posterior condensation forms what?
Extensors and supinators
Anterior condensation forms what?
Flexors and pronators
When does limb rotation happen?
6-8 weeks
Upper libs rotate how?
90 degrees laterally
What does the rotation of limbs do that is important to dermotomes?
Spiral around limbs
What does the lateral mesoderm secrete to control growth?
FGF10
What does FGF10 induce?
Thickening of ectoderm apical ectoderm ridge
What does the AER express?
FGF 4 & 8
