Lecture 15 (Exam 2) Flashcards
All skeletal muscle originates in either _______ or _______.
Somites
Somitomeres
This type of cell originates in somites. They resemble mesenchymal cells and are restricted to muscle-forming line. They are mitotic.
Myogenic cells
This type of cell is derived from myogenic cells. They are post-mitotic.
Myoblasts
These are formed when myoblasts line up and adhere to one another. They require calcium-dependent CAMs and are involved in mRNA and protein synthesis.
Myotubes
Myotubes are characterized by the appearance of ______, ______, ______, and ______.
Actin
Myosin
Troponin
Tropomyosin
Myotubes are involved in the formation of _______ with sarcomeric arrangement, and their nuclei move to the periphery.
Myofibrils
Myotubes eventually develop into…
Muscle fibers
These cells attach to myotubes before basal lamina is laid down and is located between the sarcolemma and basal lamina of myofiber. They are mitotic and myogenic. They are able to fuse with muscle fiber and provide for growth.
Satellite cells
T/F. Satellite cells form new muscle fibers.
False. Satellite cells do NOT form new muscle fibers.
Satellite cells are generally quiescent and function as ______ cells. They can become mitotic in times of stress.
Stem
Satellite cells can become mitotic in times of stress. They have a ______ receptor which is the binding site for ______. This allows the cells to give rise to myogenic precursor cells. They replace damaged muscle by proliferating, fusing, and differentiating into skeletal muscle fibers.
C-Met
HGF (Hepatic growth factor)
(PRIMARY/SECONDARY) myotubes are formed by the fusion of the earliest (embryonic) myoblasts. They may already be distinguished as fast or slow in some species. Differentiation occurs before innervation.
Primary
Secondary myotubes are smaller. They are formed alongside primary from late (fetal) myoblasts. The presence of ______ ______ may be necessary to form secondary myotubes. They are contained within the same basal lamina and are electrically coupled.
Motor axons
Myogenic are kept in the labile state by…
FGF
TGF-B
The loss of the mitotic ability of myogenic cells is due to ______. This is produced by myogenic cells in response to myogenic regulatory factors.
p21
The myogenic regulatory factors include the _____ family. They are a group of 4 helix-loop-helix transcription factors, and are able to convert non-muscle cells to cells capable of expressing muscle proteins.
MyoD
The MyoD myogenic regulatory factors form dimers and bind to the E box in the enhancer region of myogenic genes. Binding is enhanced when _____ (transcription factor) replaces one member of the dimer to form a heterodimer.
E12
The MyoD myogenic regulatory factors form dimers and bind to the E box in the enhancer region of myogenic genes. Transcriptional inhibitor _____ can replace one member of the MyoD homodimer to form a heterodimer, resulting in poor binding ability.
id
Occurring in the somites, _____ and _____ can separately activate MyoD and cause myogenic cells to become myoblasts.
Pax-3
Myf-5
Increasing levels of MyoD along with _____ result in expression of myoblast genes by myoblasts and expression of _______.
Myf-5
Myogenin
Myogenin results in expression of _______ genes and ______.
Myotube
Myf-6
______ leads to expression of myofiber genes.
Myf-6
Note that actual morphogenesis of muscles is dependent on associated ________ ________ framework.
Connective tissue
(EPAXIAL/HYPAXIAL) muscles arise from dorsal lip of myotome.
Epaxial
