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SKELETAL MUSCLE HISTOLOGY
BY
DR. MUDASSAR ALI ROOMI (MBBS, M. PHIL)
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Skeletal muscle
Makes the flesh of animals
Pink in colour due to presence ofmyoglobin and capillaries.
Muscle fibers are arranged in fasciculi
Endomysium= C.T. covering of onemuscle fiber
Perimysium= C.T. covering of onemuscle fascicle
Epimysium= C.T. covering of wholemuscle
Blood vessels penetrate the musclewithin the C.T. septa and form a richcapillary network in the endomysium.Lymphatic vessels and larger bloodvessels are found in the other C.T.layers.
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CONNECTIVE TISSUE
IN SKELETAL MUSCLE
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Skeletal muscle fibers
shape: cylindrical
length: 1-40 mm
Diameter: 10-100 um
Nuclei: multiple
(35/mm),
subsarcolemmal.
Capillaries are present
in the endomysium
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How multinucleated skeletal muscle fibers
are produced!!
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sarcomere
Definition: Sarcomere is the functional unit of
contraction in skeletal muscle.
Its length is 2-2.5 um
Sarcomere is the portion b/w two successive z
discz.
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skeletal muscle fibers show cross-striations of alternating light and dark
bands.
The darker bands are called A bands (anisotropic or birefringent in
polarized light)
the lighter bands are called I bands (isotropic, do not alter polarized light).
I band is seen to be bisected by a dark transverse line, the Z line (Ger.
Zwischenscheibe, between the discs).
A band shows the presence of a lighter zone in its center, the H zone
Bisecting the H zone is the M line
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Sarcotubular system
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Skeletal muscle
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SKELETAL MUSCLE
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HOW TO DRAW
IT!!!!
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Skeletal muscle
IDENTIFICATION POINTS:
1. Well marked Cross
striations
2. Cylindrical fibers
3. Many sub-sarcolemmal flat
nuclei
4. endomysium and
perimysium present
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Some important definitions
Hypertrophy: increase in the size of tissue due
to increase in size of cells.
Atrophy: decrease in the size of tissue due to
decrease in the size of cells.
Hyperplasia: increase in the size of tissue due
to increase in the number of cells.
Motor unit: all the muscle fibers supplied by
one motor neuron.
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