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8/12/2019 Lecture 10 Muscle Histology Titus
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Muscle Histology
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Types of Muscle Tissue
Skeletal muscle
Cardiac muscle
Smooth muscle
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Types of Muscle Tissue
SkeletalAttach to and move skeleton
40% of body weightFibers = multinucleate cells (embryonic cells fuse)
Cells with obvious striations
Contractions are voluntary
Cardiac:only in the wall ofthe heart
Cells are striated
Contractions are
involuntary (notvoluntary)
Smooth:walls of hollow organsLack striations
Contractions are involuntary (notvoluntary)
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Similarities
Their cells are called fibersbecause they
are elongated
Contraction depends on myofilaments
Actin
Myosin
Plasma membrane is called sarcolemma
Sarcos= flesh
Lemma= sheath
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Types of skeletal muscle fibers
Fast, slow and intermediate
Whether or not they predominantly use oxygen toproduce ATP (the energy molecule used in musclecontraction) Oxidative aerobic (use oxygen)
Glycolytic make ATP by glycolysis (break down of sugarswithout oxygen=anaerobic)
Fast fibers: white fiberslarge, predominantlyanaerobic, fatigue rapidly (rely on glycogen reserves);most of the skeletal muscle fibers are fast
Slow fibers: red fibershalf the diameter, 3X slower,but can continue contracting; aerobic, more mitochondria,myoglobin
Intermediate: in between
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Type 1 muscle fibers are high in oxidative
activity, low in glycolytic activity and are
red grossly because of a high content of
myoglobin and mitochondrial cytochromes.They contract slowly, but are capable of
repeated or continuous contraction. The
mnemonic "ONE SLOW RED OX*"provides a useful image to help remember
the characteristics of this fiber type.
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Type 2 muscle fibers are low in oxidative
activity and high in glycolytic activity. They
are white grossly and are capable of rapid
contraction, but cannot maintain repeatedcontraction indefinitely. The mnemonic
"TWO FAST WHITE SUGAR*"helps
recall these features. Remembering thesesimple details demystifies the otherwise
bewildering array of histochemical stains
that can be applied to frozen sections of
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ATPase pH 9.4 (Light-type1)
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NADH-TR(dark-type1)
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SDH(blue mitochondria)
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As a general rule, a "checkerboard"
appearance is the norm, with no single
muscle fiber entirely surrounded by
muscle fibers of its own type. Whengroups occur and are well-developed, the
question of denervation-reinnervation must
be raised.
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Abnormal type1&2 formation