chapter 6 muscle tissue. composition muscle cell+loose connective tissue ● muscle cell →muscle...
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Chapter 6Chapter 6muscle muscle tissuetissue
Composition muscle cell+loose connective tissue
● muscle cell →muscle fiber, sarcolemma, sarcoplasm,
sarcoplasmic reticulum ● classification: skeletal muscle, cardiac muscle, smooth muscle striated muscle, nonstriated muscle voluntary muscle , involuntary muscle
introduction:
skeletal muscleskeletal muscle
epimysium 肌外膜
perimysium 肌束膜
endomysium 肌内膜
function:
supporting
connection
nourishment
protection
1. microstructure: cylindrical: 1 ~ 40mm length,
10 ~ 100µm in diameter
elongated nuclei:
beneath the sarcolemma myofibril: parallel to long axis
light band: isotropic → I band
dark band: anisotropic→ A band
cross striation
cross section: Cohnheim field
high magnification:
A band: H band, M line; I band: Z linesarcomere=1/2 I+A+ 1/2 Istructural and functional unit a part of fibril between the neighboring z lines
Z 线
I 带 A 带
M 线
2. ultrastructure :1 ) myofibril: myofilaments
thick filament :
A band1.5 µm long 15nm in diameter
thin filament: z line
1µm long
5nm in diameter one thick filament is surrounded by 6 thin ones one thin filament is surrounded by 3 thick ones
molecular structure of myofilaments:
1. thick filament: myosin bean sprout shape : head+ rod ATPase, connecting ATP, head can bend--- combine with actin cross bridge 横桥
头( ATP 酶)
杆
2. thin filament: actin: globular subunits spiral two strands
tropomyosin:two strands of polypeptidescovering the active point of actin
troponin: TnT 连接亚单位
TnI 连接抑制亚单位 ,
TnC 钙结合亚单位 C
T
I
2). transverse tubule: ● vertical to the axis of the cell ● encircle the boundaries of the A-I bands of each sarcomere function: transmit exciting to each sarcomere
T 小管
3). sarcoplasmic reticulum: SER between T tubules surrounded each fibrile longitudinal tubule terminal cisternae 终池
triad : 2 terminal cisternae and T tubule calcium pump=ATPase function: regulate the concentration of calcium in sarcoplasma
肌浆网
三联体
3.The contraction mechanism of skehetal muscle
sliding filament hypothesis
Ca CaCa Ca
1234
cardiac muscle cardiac muscle 1. microstructure: branches intercalated disc ovoid nucleus mitochondria glycogen lipochrome cross striation
2. Ultrastructure characters:
• myofilament bundles•T-tubules at Z line level• small terminal cistermae (diad)•intercalated disc at z line level
intercalated disc transverse position: intermediate junction , de
smosome longitudinal position: gap junctionfunction: transmit chemical massa
ge and electric impulse
smooth musclesmooth muscle
1. microstructure:
spindle shape
elongated ovoid nucleus spiral,pleated 20--500µm (in pregnant uterus) arrangement: bundle or layers
2. ultrastructure:
• small vesicle: ( sarcoplasmic reticulum)• dense patch ( area), dense body intermediate filaments (10nm )
• caveola (T-tubule)
contractile unit:
thin : thick filaments = 12-30:1 cylindric, 8-16nm, myofilament unit=contractile unit: