Lect. 24 - Muscular Development Flashcards Preview

Embryo Exam II > Lect. 24 - Muscular Development > Flashcards

Flashcards in Lect. 24 - Muscular Development Deck (22):
1

Myoblast stage

Derived from myogenic cells; postmitotic

2

Myotube stage

Formed when myoblasts line up and adhere to one another; requires Ca2++-dependent CAMs; involved in mRNA and protein synthesis; characterized by appearance of actin, myosin, troponin and tropomyosin; formation of sarcomeres; nuclei move to periphery

3

What is the role of satellite cells?

Located b/w sarcolemma and basal lamina; mitotic and myogenic; able to fuse w/ muscle fiber and provide for growth; note that satellite cells do not form new muscle fibers

4

Primary myotubes

Formed by fusion of earliest (embryonic) myoblasts; may already be distinguished as fast or slow in some species; differentiation occurs before innervation

5

Secondary myotubes

Smaller than primary; formed alongside primary from late (fetal) myoblasts; presence of motor axons may be necessary to form secondary myotubes; contained w/I same basal lamina and are electrically coupled

6

What is the role of FGF and TGF-beta in the differentiation of muscle tissue?

Maintain myogenic cells in the labile state

7

MyoD family

Able to convert non-muscle cells to cells capable of expressing muscle proteins; helix-loop-helix TF; forms dimer and binds to E box in enhancer region of myogenic genes; binding is enhanced when E12 replaces one member of the dimer to form a heterodimer; transcriptional inhibitor id can replace one member of the MyoD homodimer to form a heterodimer resulting in poor binding ability

8

Role of pax-3 and myf-5

Separately can activate MyoD and cause myogenic cells to become myoblasts; increasing Myf-5 along w/ MyoD results in expression of myoblast genes by myoblasts and expression of myogenin

9

Role of Myf-6

Myogenin results in expression of myotube genes myf-6; leads to expression of myofibers genes

10

Role of pax-7

Along w/ pax-3 induces MyoD w/ proliferation factors FGF and TGF-beta

11

Epaxial muscles of the trunk arise from ?

Dorsal lip of myotome

12

Epaxial tendons of the trunk arise from ?

Syndetome layer w/I somites

13

Hypaxial muscles of the trunk arise from?

Ventral buds of myotome

14

Tendons of Hypaxial muscles of the trunk arise from?

Lateral plate mesoderm

15

Limb muscles arise from?

Ventrolateral dermomyotome

16

Tendons of limb muscles arise from?

Lateral plate mesoderm

17

Muscles of the head and the neck are mostly derived from?

Par axial somitomeres

18

Extraocular muscles arise from?

Pre chordal plate

19

Most of the cranial musculature is derived from?

Unsegmented paraxial mesoderm

20

Some cranial musculature (lower jaw) is derived from ?

Splanchnic mesoderm

21

Cardiac muscle is derived from?

Splanchnic mesoderm

22

Myogenic cell stage

Originate in somites; resemble mesenchymal cells; restricted to muscle-forming line; mitotic cells