chapter 6 muscle tissue. composition muscle cell+loose connective tissue ● muscle cell →muscle...

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: