MSK Embryology Flashcards
What forms the dermatomes and myotomes embryonically?
Somites
What makes up the ventral portion of the somite?
Sclerotome
What does the sclerotome form?
Vertebrae
Ribs
What makes up the dorsal portion of the somite?
Dermatomyotome
What does the dermatomyotome form?
Dermis
Muscle
How do dermatomyotomes get their nervous supply?
Develop in association within a specific neural level - take nerve supply with them from neural tube as a spinal nerve
When do the limbs begin to develop?
Week 4
Which limbs start to develop first?
Upper limbs
When are the limbs well differentiated by?
Week 8
What is the precursor structure for the limbs?
Limb buds
What forms the limb buds?
Mesenchymal cells in the somatic layer of the lateral plate mesoderm
What is the structure of limb buds?
Central core of undifferentiated mesoderm
Tipped with a layer of ectoderm - apical ectodermal ridge (AER)
How do limbs grow?
Proliferation of mesoderm
How do the digits form?
Mesenchym condenses into plates forming cartilaginous plates of the bones
AER breaks up and is only maintained over the tips
Interdigital spaces sculpted by apoptosis
How do the limbs rotate?
Arms - rotate out
Legs - rotate in
