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BIOL 302 – Muscle

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University of Waterloo
BIOL 302
Mungo Marsden

BIOL 302 – Histology – Muscle Functions  Contraction – generation of force.  Movement  Structural support  Glands  Physiology Muscle Tissue Metabolism  Contractions are ATP dependent  Highly metabolic – burn a lot of fuel and energy to contract  Many mitochondria – generate lots of power  Highly vascularized – nutrient and oxygen supply via capillaries Muscle Tissue Types  Identify according to: organization, nuclei/cell morphology, contractile apparatus, junctions  Skeletal – striated  Cardiac – striated  Smooth – no striations  Myoepithelial – glands; can contract and expel secretions of exocrine glands  Myofibroblast – scar tissue; contract by using smooth muscle type actin-myosin complex. These cells are then capable of speeding wound repair by contracting the edges of the wound.  Pericytes – blood vessels; regulate capillary blood flow, the clearance and phagocytosis of cellular debris, and the permeability of the blood–brain barrier. Skeletal Muscle Function  Voluntary: moves skeleton and organs Components  Epimysium: layer of connective tissue, which covers the entire muscle.It is composed of dense irregular connective tissue.  Perimysium: sheath of connective tissue that groups muscle fibres into bundles.  Endomysium: wispy layer of areolar connective tissue that covers each individual muscle fiber. It also contains capillaries and nerves. It overlies the muscle fiber's cell membrane: the sarcolemma.  Sarcolemma: cell membrane of striated muscle fibre cell.  Sarcoplasm: comparable to cytoplasm, but of muscle cells.  Sarcomere: functional or contractile unit of a muscle cell.  Myofibril: cylindrical bundle of contractile proteins found within the muscle cell.  Filaments: thin (actin); thick (myosin) Characteristics  Has repeated banding pattern of light and dark bands (myofibrils)  Multiple nuclei, located on periphy of the cells.  Fibres run parallel to each other  XS: Polygonal shaped cells; in bundles (fascicles); nuclei located on periphery  LS: long with visible striations; thin nuclei located on periphery; unbranched Sarcomere  Z-line: junction  M-line: middle; stays same size  A-band: actin (thin) + myosin (thick); stays same size 
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