Lecture 20: Muscular Development Flashcards
What is the order of the stages of muscle tissue morphogenesis?
Myogenic cell–>Myoblast–>Myotube–>Muscle fiber
What do myogenic cells originate from?
Somites
T/F: Myogenic cells are postmitotic.
False, myogenic cells are still mitotic. Myoblasts are postmitotic
When are myotubes formed?
When myoblasts line up & adhere to each other
What are myotubes characterized by?
Actin, myosin, troponin, tropomyosin, sarcomere formation, & peripheral nuclei
T/F: Satellite cells are mitotic & myogenic and form new muscle fibers.
False, do not form new muscle fibers. Provide growth of existing fibers
What occurs first, differentiation or innervation, of primary myotubes?
Differentiation:
between fast/slow fibers
What is necessary for the formation of secondary myotubes?
Nerves in primary myotubes
What signaling molecules maintain myogenic cells in mitotic state?
FGF & TGF-beta
What is the loss of mitotic capability due to?
p21
How do MyoD, E12, & Id interact to regulate muscle development?
Enhancer + MyoD homodimer = Good activation
Enhancer + MyoD-E12 heterodimer = Great activation
Enhancer + MyoD-Id heterodimer = Poor/No activation
Which factors activate MyoD?
Myf-5 & Pax-3/Pax-7
What does expression of Myf-5 & MyoD result in the formation of?
Myogenin & myoblast genes
What does myogenin result in the formation of?
Myf-6 & myotube genes
What does Myf-6 lead to the expression of?
Myofiber genes
What do epaxial muscles arise from?
Dorsal lip of myotome
What do epaxial tendons arise from?
Syndetome layer within somites
What do hypaxial muscles arise from?
Ventral buds of myotome
What do hypaxial tendons arise from?
Lateral plate mesoderm
What do limb muscles arise from?
Ventrolateral dermomyotome
What do limb muscle tendons arise from?
Lateral plate mesoderm
What are most head and neck muscles derived from?
Paraxial somitomeres
What do extraocular muscles arise from?
Prechordal plate
What is most of the cranial musculature derived from?
Unsegmented paraxial mesoderm
What is the other cranial musculature (lower jaw) derived from?
Splanchnic mesoderm
What is cardiac muscle derived from?
Splanchnic mesoderm
What do both cardiac and skeletal muscle cells express?
MADS
T/F: Cardiac musculature expresses MyoD.
False
How do early cardiac muscle cells maintain their ability to divide?
By partially disassembling their contractile apparatus prior to cell division
