Week 1 - MSK development Flashcards
What does the skull develop from?
- What are the two parts of this?
Mesenchyme (developed from neural crest cells) around the brain:
- Viscerocranium
- Neurocranium
What does each vertebra develop from?
From the sclerotome of 4 somites.
What are the two parts of an intervertebral disk?
- and what is their orientation relative to each other?
Nucleus Pulposus - inner center of disk
Annulus Fibrosis - outer ring of disk (fibrous part)
What forms the nucleus pulposus of the intervertebral disk?
The notochord
What does the annulus fibrosis develop from?
The mesoderm (connective tissue) between the vertebrae.
What are the two divisions of the of the myotome (within the thorax and abdominal regions)?
Epaxial division
Hypaxial division
What muscles are part of the epaxial division?
Back and neck muscles
What innervates the epaxial division?
dorsal rami
What muscles are part of the hypaxial division?
Trunk and limb muscles
What innervates the hypaxial division?
Ventral rami
When does muscle tissue begin to differentiate?
At week 4-5 in development
What muscle cell precursors for at 4-5 weeks of development?
Myoblasts
What is the embryonic origin of the skull (head mesenchyme)?
Neural crest cells
When do muscle cells begin to differentiate?
Week 5-6 in development
Describe the process of muscle development after the muscle cells have begun to differentiate.
- myoblasts fuse
- multinucleated myotubes
- more myoblasts added at the ends
- begin synthesizing actin & myosin
What is a myotube?
Multi-nucleated, undifferentiated contractile apparatus (sarcomere)
What is a myofibre?
Multinucleated differentiated sarcomere
What happens between week 9 and 5 months of muscle development?
Nuclei migrate to the outside of the myotube - actin & myosin organized to form contractile elements
What is the difference between primary and secondary myotubes?
Primary myotubes do not need nerve cell involvement.
Secondary myotubes need nerve cells present to form.
When does development of the limbs begin?
Week 4 of development.
What is the primary axial artery in the upper limb?
Brachial artery
What gene controls the anterior/posterior axis of limb?
Shh (Sonic Hedgehog gene)
What gene controls the dorsal/ventral axis of limb?
Wnt
What gene controls the outgrowth (proximal/distal axis) of limb?
Wnt & Shh