1. Muscle Tissue
Department of Histology and Embryology , ZhangJing

2. General description (1) components
Muscle cells: elongated ,thread-liked shape-----
muscle fibers
Cell membrane - Sarcolemma(肌膜)
Cytoplasma - Sarcoplasm (肌浆)
Smooth endoplasmic reticulum(SER)
- Sarcoplasmic reticulum(肌浆网)
Connective tissue,blood vessel, lymph-vessel
and nerve

3. Skeletal muscle

4. (2) Classification According to the structure and function
skeletal muscle: striated, voluntary
cardiac muscle: striated, involuntary
smooth muscle: unstriated, involuntary

5. Classification of muscle tissue

6. 1. Skeletal muscle

7. 1.1 The structure of skeletal muscle fiber under LM
Longitudinal section of skeletal muscle

8. 1.1 The structure of skeletal muscle fiber under LM
Longitudinal section
Shape of muscle fiber: Long cylindrical, No branched,
Cross striations.
Nuclus: Multinucleated, oval, just beneath the
sarcolemma (at its periphery).
Each cell has numerous oval nuclei at its periphery,
Sarcoplasm: filled with longitudinal parallel-arranged
myofibrils（肌原纤维）.

9. * Sarcomere: a segment of myofibril extending from one Z line to next Z line, which is composed of 1/2 I band, A band and 1/2 I band ,which is the smallest structural and functional unit of skeletal muscle fiber.

10. Transverse section of skeletal muscle

11. 1.1 The structure of skeletal muscle fiber under LM
Transverse section
Shape of muscle fiber: Irregular and polyhedral
Nuclear: periphery, round
Myofibril in sarcoplasm :red dots

12. 1.2.1 Myofibril: myofilament（肌丝）
1.2 The structure of skeletal muscle fiber under EM
1.2.1 Myofibril: myofilament（肌丝）
（thick myofilament and thin myofilament)
(1) Arrangement：

13. (2) Molecular structure of myofilament
1)Thick myofilament: Myosin（肌球蛋白)

14. 2)Thin myofilament: actin(肌动蛋白), tropomyosin(原肌球蛋白) and troponin(肌钙蛋白)

16. 1.2 The structure of skeletal muscle fiber under EM
1.2.2 Transverse tubule
(T tubule):
---Definition: sarcolemma invaginate into sarcoplasm to form a transverse distributed tubular system
---Location: A-I junctional part
---Function: transfer the information into sarcoplasm

17. 1.2 The structure of skeletal muscle fiber under EM
1.2.3 Sarcoplasmic reticulum:
---Definition:
smooth endoplasmic reticulum
--- longitudinal tubule:
A longitudinal distributed tubular system formed by smooth endoplasmic reticulum
---terminal cisternae:

18. 1.2 The structure of skeletal muscle fiber under EM
1.2.3 Sarcoplasmic reticulum:
---Structure:
* triad: one T-tubule +two terminal cisternae
---Function: there are calcium pump /gap on membrane, so it can store and release calcium ions

19. 1.2 The structure of skeletal muscle fiber under EM
1.2.4 Mitochondria, glycogen, lipid droplet

20. 1.3 Sliding filament mechanism
During the contraction, the A band remained constant in length, while the I band and H band both decreased in width, which suggest that the thin filament slide along the thick filament toward the M –line.

21. 1.3 Sliding filament hypothesis

22. 1.4 Construction of skeletal muscle
Skeletal muscle is fixed on bone by tendons.
Epimysium （肌外膜）: DCT
Perimysium （肌束膜）
Endomysium （肌内膜）
Muscle satellite cell: differentiate and proliferate

23. 2.Cardiac muscle

25. 2.1 The structure of cardiac muscle fiber under LM

26. 2.1 The structure of cardiac muscle fiber under LM
Longitudinal section
Shape of muscle fiber: Short cylindrical, connect with
neighboring cells form a network
by their branches,
cross striations are less distinct.
Nuclus: one or two centrally located ovoid nuclei.
Fiber connect with each other by intercalated disc
(闰盘).

27. Cardiac muscle ,specific stain

28. 2.1 The structure of cardiac muscle fiber under LM

29. 2.1 The structure of cardiac muscle fiber under LM
Transverse section
Round or irregular with a nucleus or not.
The cytoplasm staining of perinuclear region is lighter.

30. 2.2 The structure of cardiac muscle fiber under EM
Similar to skeletal muscle, composed of thick, thin myofilament and have sarcomere.
①     Myofibril have different diameter, the boundary of myofibril is not very clear.

31. 2.2 The structure of cardiac muscle fiber under EM
② Thansverse tubule is thicker, located at Z-line level.
③ Sarcoplasmic reticulum is not well-developed, form less terminal cisternae.
* diad: one T-tubule + one terminal cisternae

32. 2.2 The structure of cardiac muscle fiber under EM
Intercalated disc

33. ④ intercalated discs step-liked structure
2.2 The structure of cardiac muscle fiber under EM
④ intercalated discs step-liked structure
transverse portion:
-intermediate junction
-desmosome
longitudinal portion:
-gap junction communication
connection

34. 3. Smooth muscle

35. 3.1 The structure of smooth muscle fiber under LM

36. 3.1 The structure of smooth muscle fiber under LM
Longitudinal section
Shape of muscle fiber: Spindle shaped ,without cross
striation.
Nuclus: one centrally located ovoid nuclei.
Transverse section
Shape of muscle fiber: Round or irregular , variable diameter.
Nuclus: Nuclei are seen only in the thicker profiles.

37. 3.2 The structure of smooth muscle fiber under EM

38. 3.2 The structure of smooth muscle fiber under EM
粗肌丝：细肌丝=1：12

39. 细肌丝——
——粗肌丝
Gap junction exists between smooth muscles

41. 名 称 骨骼肌 心肌 平滑肌 形 状 细胞核 横 纹 闰 盘 肌原纤维 分布 功能 △三种肌纤维比较 长圆柱形 短圆柱形 细长梭形
名 称
骨骼肌 心肌
平滑肌
形 状
长圆柱形
短圆柱形
细长梭形
细胞核
多个，位于细胞周边
一个，位于细胞中央
横 纹
有，明显
有，不明显 无
闰 盘 有
肌原纤维 明显
不明显 分布
附着于骨骼 心壁
内脏，血管壁 功能
随意肌，
不随意肌