Muscular Tissue
Jun Zhou (周俊)
School of Medicine, Zhejiang University
20140318
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Overview
1) components:
--cell: muscle fiber-myofiber




elongated thread-liked
Sarcolemma（肌膜）
Sarcoplasm（肌质）
Sarcoplasmic reticulum（肌质网）: SER
--extracellular G.S: CT with BV, LV and N
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2) classification
According to the structure and function
 skeletal muscle (骨骼肌): striated, voluntary
 cardiac muscle (心肌): striated, involuntary
 smooth muscle (平滑肌): unstriated, involuntary
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Skeletal muscle
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 Epimysium（肌外膜）: DCT
 Perimysium（肌束膜）
 Endomysium（肌内膜）
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LM:
 long cylindrical 10-100um in diameter, 1-40mm long
 multinucleate, nuclei are ovoid, distributed under
sarcolemma
 filled with longitudinal parallel- arranged myofibrils
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Skeletal Muscle
 Cells are long multinucleate “cylinders”
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Endomysium
Fascicle
Myofiber
Perimysium
Identify: Endomysium, Perimysium, myofiber and fascicle
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Endomysium: connective tissue, nutrient capillaries, nerve endings
and around each myofiber a basal or external lamina
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Myofiber
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Myofibril:
 1-2um in diameter
 cross striation:
 light band -I band
 dark band- A band
--A band: M-line, H-band
--I band: Z-line
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Definitions
Isotropic (各向同性)
Anisotropic (各向异性)
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A band : Anisotropic (各向异性)
I band: Isotropic (各向同性)
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H Band is light and in the center of the A Band
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Sacromere（肌节）: 1/2 I +A + 1/2 I
the smallest structural and functional unit of
myofibril
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EM:
1.Transverse tubule (T tubule):



横小管
definition: sarcolemma invaginate into
sarcoplasm to form a transverse
distributed tubular system
location: A-I junctional part
function: transfer the information into
cytoplasm
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2.Sarcoplasmic reticulum:






肌质网
smooth endoplasmic reticulum
longitudinal tubule ( L tubule )
terminal cisternae (终池)
Triad ( 三 联 体 ): one T-tubule +two
terminal cisternae
calcium pump proteins
store and release calcium ions
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3.Myofibril (肌原纤维)
thick myofilament
 thin myofilament

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Skeletal Muscle
 Organizational Hierarchy
Muscle is composed of fascicles
Fascicle (smallest) is composed of myofibers
Myofiber is composed of myofibrils
Myofibril is composed of myofilaments
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Thick myofilament
1.5 um long, 15 nm in diameter
 composed of myosin (肌球蛋白)
-rob: in bundles
-head: cross bridge- binding site (ATPase activity)

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Thin myofilament


1 um long,
5 nm in diameter
A. Actin (肌动蛋白)- binding site
B. Tropomyosin (原肌球蛋白)
C. Troponin (肌原/钙蛋白)
-Tn T: bind to tropomyosin
-Tn C: binds to calcium ions
-Tn I: inhibit actin-myosin interaction
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Myofibril
A
is that evident
portion
the
apparatus
Issarcomere
cross banding
Define of
aatsarcomere.
thecontractile
level of the
myofibril?
between and attaching to two Z lines.
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Myofibril
consistunit.
of myosin.
The sarcomereThick
is themyofilaments
smallest contractile
It consists of a
precisely organized
array
of myofilaments.
Myosin
is ONLY
found in the A Band
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Myofibril
Thin myofilaments consist of Actin, tropomyosin and troponin.
Thin myofilaments are found in BOTH the A Band and I Band
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Myofibril
M Line, in the center of the H Band, consists of proteins that hold
myosin filaments together.
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Myofibril
Z Line.
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Electron Micrograph of Human Skeletal Muscle
Myofibril
Micrograph Provided by Ernest Whitter
Dark granules are glycogen
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Electron Micrograph of Human Skeletal Muscle
Sarcomere
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Micrograph Provided by Ernest Whitter
Electron Micrograph of Human Skeletal Muscle
A Band
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Micrograph Provided by Ernest Whitter
Electron Micrograph of Human Skeletal Muscle
Z Line
M Line in H
Band
I Band
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Micrograph Provided by Ernest Whitter
Sliding filament hypothesis (肌丝滑动学说)
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Cardiac muscle
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LM
 short column in shaped, 100um long,15um in
diameter, with branches
 1-2 ovoid nuclei, centrally-located
 striated, but no very clear
 intercalated disc
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EM
 T tubule at Z-line level
 less terminal cisternae
 diad(二联体):
one T-tubule + one terminal cisternae
 Numerous mitochondria
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intercalated discs
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Smooth muscle
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LM
 elongated, spindle-shaped cells,
diameter, 200( 20-500)um long
 rob-liked or ovoid nucleus
 no striation, no myofibril
8um
in
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Cross Section
Longitudinal Section
Smooth Muscle
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EM
 caveola: sarcolemme
invaginate into cytoplasm
 dense patch (密斑): under sarcolemma
dense body (密体): in sarcoplasm
 intermediate filament:
/composed of desmin(结蛋白)
/10nm in diameter
/connect between dense body
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 thick filament: myosin, 15 nm
thin filament: actin, 5 nm-fixed on dense patch or body
 contractile unit ( 肌 丝 收 缩 单 位 ): several thick
filament and thin filament aggregate
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