Muscular TissueMuscular Tissue

Prof. Ji-Cheng LiProf. Ji-Cheng Li

(Zhejiang University School of Medicine)(Zhejiang University School of Medicine)

General description

1) components:

---cell: muscle fiber--myofiber

• elongated thread-liked

• sarcolemma (cell membrane)

• sarcoplasm (cytoplasm)

• sarcoplasmic reticulum (SER )

---extracellular G.S: CT with BV, LV and N

2) classification

According to the structure and function

• skeletal muscle: striated voluntary m.

• cardiac muscle: striated involuntary m.

• smooth muscle: unstriated involuntary m.skeletal muscle cardiac muscle smooth muscle

Skeletal muscleSkeletal muscle

Often called striated or voluntary muscle– Has striations that are visibl

e under light microscopy

– Under voluntary control

– Attached to skeleton ( skeletal)

• Characteristics of

Skeletal Muscles

– Muscle cells are

elongated fibers with

many peripheral nuclei

– Each muscle fiber

contains many myofibrils

– Each myofibril contains

many microfilaments

Connective tissue coverings (responsible for force transduction):

Epimysium: surround entire muscle

Perimysium: surround fascicle

Endomysium: surround individual fibers

Epimysium

Entire musclePerimysium

Fasciculus of muscle fibres Endomysium

A muscle fibre

1)      Microstructure of skeletal muscle fiber

① long cylindrical 10-100um

in diameter,1-40mm long

② multinucleate, nuclei are ovoid, distributed under sarcolemma

③ filled with longitudinal parallel-arranged myofibrils

Longitudinal section Transverse section

muscle fiber

myofibril

Thin Filaments Thick Filaments

myofibril:• 1-2um in diameter

• cross striation: light band --I band,

dark band-- A band

I bandA band

H-band

Z-line M-line

--A band: M-line, H-band--I band: Z-line

--A band (except H band):

Thin Filaments

Thick Filaments

• H band:

only Thick Filaments

--I band:

only Thin Filaments

sacromere:1/2 I band, A band ,1/2 I band the smallest structural and functional unit of

myofibril

sacromere

2) Ultrastructure of myofiber myofibril:

---thick myofilament: • Composed of myosin:

---thin myofilament: • Compose of• A. actin• B. tropomyosin• C. troponin:

Transverse tubule

(T tubule):

---definition: sarcolemma and basement membrane invaginate into sarcoplasm to form a transverse distributed tubular system

---location: A-I junctional part

---function: transfer the information into cytoplasm

③     Sarcoplasmic reticulum:---definition: A longitudinal distributed tubular s

ystem formed by smooth endoplasmic reticulum

Sarcoplasmic reticulum

---structure: H-A band: longitudinal enclose myofibril-- longitudinal tubule

terminal cisternae: flattened sac, A-I junction

•triad: one T-tubule + two terminal cisternae

---function: there are calcium pump proteins (ATPase) on membrane, so it can store and release calcium ions

triad

Cardiac muscleCardiac muscle

1) Microstructure of cardiac muscle• ① short column in shaped, 100um long,15um in d

iameter, with branches, the branches associated with each other to form a network

• ②  1-2 nuclei, centrally-located• ③  striated, but no very clear• ④  intercalated disc: junctional part• LM: dark striation across the cardiac fibers

Cardiac muscleCardiac muscle

Cardiac muscle: show Cardiac muscle: show intercalated disc

2) Ultrastructure of cardiac muscle

similar to skeletal muscle, composed of thick, thin filament and have sarcomere

Different:

① myofibril have different diameter, the boundary of myofibril is not very clear

② transverse tubule are thicker, located at Z-line level

(skeletal muscle : A-I junctional part)

③ sarcoplasmic reticulum is not well-developed, form less terminal cisternae

④diad: one T-tubule + one terminal cisternae

(skeletal muscle : triad) skeletal muscle

cardiac muscle

diad

triad

 ④ intercalated discs transverse portion

longitudinal portion

transverse portion : connection -intermediate junction -desmosome longitudinal portion: communication -gap junction

transverse portion

longitudinal portion

Smooth muscleSmooth muscle

1) microstructure of smooth muscle ①     elongated, spindle-shaped cells, 8 um in di

ameter, 200( 20-500)um long ②     only one nucleus ③     no striation, no myofibril

smooth muscle

smooth muscle

Neuroanglion

2) ultrastructure of smooth muscle①     caveola on sarcolemme invaginate into cytoplasm②  dense patch: under sarcolemma dense body: in sarcoplasm③     intermediate filament:

caveola dense body dense pach

smooth musclesmooth muscle under SEM under SEM

Compare with three muscle tissues

• 1. The location of T tubules of cardiac muscle differ from those of skeletal muscle, the former lie at the

• A. A-I junctions B.I bands

• C. A bands D.M lines

• E. Z lines√

• 2. Sarcoplasmic reticulum of muscle fiber is composed of

• A. lysosome B. mitochondria

• C. microsome D. RER

• E. SER√

3.The cell junction which transmit rapidly an electrical impulse between adjacent smooth muscle cells is

• A. tight junction B. intermediate junction

• C. gap junction D. desmosome

• E. semidesmosome√

• Questions:

• Describe the characteristics of muscle tissue.

• Compare the similar with the difference for three kinds of muscle cells according to their fine structure and ultrastructure.