Lecture 7-0

Lecture 7-0 - Muscle Tissue Review PSIO 445/545 Muscle...

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Muscle le Tissue Rev PSIO 445/545 view
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Muscle tissue is: A collection of individual mus Functions include locomotion through hollow organs Origins of muscle: At the developmental stage, the ferti on its developmental path, the enlarg the endoderm, mesoderm, and ectod to muscle tissue. Figure adapted from images taken fro http://www.unige.ch/cyberdocumen http://www.sciencedaily.com/article scle cells designed to contract and generate t n, heat production, maintenance of posture, a Figure 1 tilized egg, or zygote, becomes the blastocyst rging mass develops three distinct “germ laye derm. As you can see on the figure above, th rom: nts/theses2004/HeQ/these_body.html and es/g/germ_layer.htm tension and propulsion of material t. As the blastocyst continues ers”. These germ layers are he mesoderm is the precursor
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From a muscle standpoint, the mesoderm gives rise to myogenic stem cells (figure 2). These stem cells can have different fates. One path leads to the creation of fibroblasts and connective tissue. The path we are interested in is that which results in the creation of the myoblast. Myogenic stem cells that are programmed appropriately become myoblasts, the true precursors of muscle cells (fibers). As shown in figure 3, the dividing myoblasts are bathed in endocrine and paracrine growth factors which further move them along the developmental path. The myoblasts are then committed to this differentiation path and align themselves, fuse together, and form the myotube. Myotubes further mature to form the muscle fiber. As is indicated in figure 3, during each fusion process the each nucleus from the individual myblasts are retained resulting in a multinucleated muscle fiber. This multinucleated form is a hallmark of skeletal muscle. Mesoderm Myogenic Stem Cells Myoblast Fibroblast Myotube Muscle Connective Tissue Figure 2 Figure 3
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A characteristic of mature muscles fibers is the existence of satellite cells. During the developmental process that results in the creation of muscle fibers, some of the myoblasts are converted to satellite cells. The
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Lecture 7-0 - Muscle Tissue Review PSIO 445/545 Muscle...

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