Musculoskeletal Development II Flashcards
What are the 4 stages in the differentiation of skeletal muscle tissue? Describe 3/4 stages
Myogenic cells:
- Originate in somites
- Resemble mesenchymal cells
- Mitotic cells
Myoblasts:
- Derived from myogenic cells
- Postmitotic
Myotubes:
-Formed when Myoblasts line up and adhere to each other
Muscle Fibers
What 2 factors keep Myogenic cells in the mitotic state?
FGF
TGF- beta
What do Myotubes require?
Calcium-dependent CAMs
What are Myotubes involved in?
mRNA and protein synthesis
What characterizes Myotubes?
The appearance of Actin, Myosin, Troponin, and Tropomyosin
Nuclei moving to the periphery
Where do Satellite cells attach?
To myotubes before the basal lamina is laid down
Located between the sarcolemma and the basal lamina of the myofiber
What is the function of satellite cells in terms of muscle growth?
Act as stem cells
Can become mitotic in times of stress:
- When Hepatic growth factor binds to the C-Met receptor
Gives rise to myogenic precursor cells to replace damaged skeletal muscle
Myotubes can be broken down into primary and secondary myotubes. When do primary myotubes form?
After fusion of early (embryonic) myoblasts
This differentiation occurs before innervation
Myotubes can be broken down into primary and secondary myotubes. When do secondary myotubes form?
Formed alongside primary myotubes from late (fetal) myoblasts
This differentiation occurs after innervation
*Smaller than primary
What causes myogenic cells to lose their mitotic capability?
p21- produced by myogenic cells in response to myogenic-regulatory factors, MyoD family
Describe myogenic-regulatory factors, MyoD family
Able to convert non-muscle cells to cells capable of expressing muscle proteins
What is the pathway from myogenic precursors to myofibers?
Pax-3 and Myf-5 separately activate MyoD and cause myogenic cells to become myoblasts
Myoblasts express myogenin
Myogenin results in the expression of myotube genes of Myf-6
Myf-6 leads to the expression of Myofibers
Limb muscles arise from what?
The ventrolateral demomyotome
Tendons of limb muscles arise from what?
Lateral plate of the mesoderm
Where is cardiac muscle derived from?
Splanchnic mesoderm
Early cardiac muscle does not express what?
MyoD
Cardiac muscle cells remain as _______ cells and attach to each other via _______ ______
Mononucleated
Intercalated Discs
