Histology of muscle -Histology of muscle

1. HISTOLOGY OF MUSCLE TISSUE
Lecture By
Dr.N.Mugunthan.MS.,DNB. MNAMS., PhD.,
Associate Professor
MGMC&RI

2. Try to identify this slide
© Dr.N.Mugunthan 2

3. Objectives
• Features of muscle tissue
• Types of muscle
• Microstructure of each type of muscle
• Applied histology
• Practical aspects
• Summary
© Dr.N.Mugunthan 3

4. Muscle tissue
• Contractile
• Cells – myocytes
• Myocytes are
elongated – muscle
fibres
• Developed from –
mesenchyme
(mesoderm)
© Dr.N.Mugunthan 4

5. Types of muscle
• Structurally and
functionally 3
distinct types of
muscle
1. Skeletal muscle
2. Cardiac muscle and
3. Smooth muscle
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6. 1. Skeletal muscle
• Skeletal muscle or
• Striated muscle or
• Voluntary muscle
• Ex: muscles of Limbs
& body wall
© Dr.N.Mugunthan 6

7. Skeletal muscle cont….
• Consists of long tubular
cells (also called muscle
fibers).
• Average length 3 cm
• (sartorius 30 cm,
stapedius 1 mm)
• Cell membrane –
sarcolemma
• Cytoplasm ( sarcoplasm)
• Contain many
peripherally placed
nuclei (up to several
hundred).
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8. © Dr.N.Mugunthan 8

9. • Muscle fibers in skeletal
muscle occur in bundles,
(fascicles)
• Connective Tissue
Covering
a) Epimysium,
b) Perimysium
c) Endomysium
• The connective tissue
transduces the force
generated by the muscle
fibers to the tendons.
Skeletal muscle cont….
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10. © Dr.N.Mugunthan 10

11. • Muscle fibers show
characteristic cross-
striations. (striated
muscle)
• Innervated by the
somatic nervous
system. (Voluntary
muscle)
Skeletal muscle cont….
© Dr.N.Mugunthan 11

12. Skeletal muscle – cross section
skeletal muscle
cells ("fibers")
skeletal
muscle cell
nuclei
blood
vessels
interlacing
bundles of
smooth muscle
© Dr.N.Mugunthan 12

13. Skeletal muscle –L.S & T.S
© Dr.N.Mugunthan 13

14. Skeletal muscle, L.S. Note the striations.
PICROSIRIUS-POLARISED LIGHT (PSP) STAIN, high
magnification. © Dr.N.Mugunthan 14

15. Contractile apparatus of
skeletal muscle
• Regular
organization of the
myofibrils gives rise
to the cross striation
• cross striation
characterizes
skeletal and cardiac
muscle.
• Sarcomeres
© Dr.N.Mugunthan 15

16. • A number of "bands" and
"lines" can be distinguished
in the sarcomeres
• I-band - actin filaments,
• A-band - myosin filaments
• H-band - zone of myosin
filaments only
• Z-line - zone of apposition of
actin filaments belonging to
two neighboring sarcomeres
• M-line - band of connections
between myosin filaments
Contractile apparatus of
skeletal muscle
© Dr.N.Mugunthan 16

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18. © Dr.N.Mugunthan 18

19. Contraction & relaxation phases at the level of the
sarcomere© Dr.N.Mugunthan 19

20. • Involuntary
• Striated muscle
• Ex: heart
2. Cardiac muscle
© Dr.N.Mugunthan 20

21. Cardiac muscle
• Myocytes contain one
centrally placed nucleus.
• Cardiac muscle exhibits
cross-striations. (Less
distinct)
• Cardiac muscle cells
often branch at acute
angles
• And are connected to
each other by
specializations of the cell
membrane -intercalated
discs.
© Dr.N.Mugunthan 21

22. • Z-line of the myofibrils
("replaced" by the
intercalated disc of the
cell membrane).
• Cardiac muscle
becomes a 'functional
synctium' to permit
the spread of
excitation.
• Innervated by the
autonomic nervous
system
Cardiac muscle cont..
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24. Cardiac muscle cont..
• Cardiac muscle does not contain
satellite cells.
• Cardiac muscle cannot regenerate.
• Fibrosis occurs.
© Dr.N.Mugunthan 24

25. 3. Smooth muscle
• Smooth or plain
muscle
• Involuntary muscle
• Non-striated muscle
• Ex: hollow viscera,
wall of respiratory
tract & blood vessels
© Dr.N.Mugunthan 25

26. Smooth muscle cont…
• Consists of spindle
shaped cells
• Smooth muscle cells
contain one
centrally placed
nucleus.
• Innervation by the
autonomic nervous
system. (Involuntary
muscle.)
© Dr.N.Mugunthan 26

27. • In the cytoplasm,
longitudinally
oriented bundles of
the myofilaments
actin and myosin are
seen.
• Myofibrils do not run
exactly longitudinally
or parallel to each
other
• Striations, therefore
not visible in smooth
muscle.
Smooth muscle cont…
© Dr.N.Mugunthan 27

28. © Dr.N.Mugunthan 28

29. Other contractile cells
1. Myoepithelial cells
2. Myofibroblasts
3. Pericytes
© Dr.N.Mugunthan 29

30. • Hypertrophy
• Hyperplasia
• Regeneration
• Atrophy / dystrophy
Applied histology
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31. • During an asthma
attack - smooth
muscle contracts
• In atherosclerosis -
smooth muscle cells
proliferate
• Lactation -
myoepithelial cells
contracts & eject the
milk
• Myofibroblasts -found
in cases of fibrosis
Applied histology
© Dr.N.Mugunthan 31

32. Practical aspects
Skeletal muscle L.S
• Longitudinal muscle
fibers
• Peripherally placed
oval nuclei
• Multiple nuclei in
each cell (>100)
• Transverse striations
• Endomysium,perimy
sium & epimysium
© Dr.N.Mugunthan 32

33. Skeletal muscle T.S
• Cross section of
muscle fibers
• Peripherally placed
nuclei
• Multiple nuclei
• Transverse striations
• Endomysium,perimy
sium & epimysium
Practical aspects
© Dr.N.Mugunthan 33

34. Cardiac muscle L.S
• Longitudinal
muscle fibers
• Branching and
anastomosing fibres
• Single centrally
placed nuclei
• Transverse striations
(less distinct)
• Intercalated disc
Practical aspects
© Dr.N.Mugunthan 34

35. 1. Skeletal muscle
2. Cardiac muscle
3. Smooth muscle
Summary
© Dr.N.Mugunthan 35

36. • Skeletal muscle L.S
• Skeletal muscle T.S
• Cardiac muscle L.S
• Smooth muscle
Summary
© Dr.N.Mugunthan 36

37. • Skeletal muscle L.S
• Skeletal muscle T.S
• Cardiac muscle L.S
• Smooth muscle
Summary
© Dr.N.Mugunthan 37

38. • Skeletal muscle L.S
• Skeletal muscle T.S
• Cardiac muscle L.S
• Smooth muscle
Summary
© Dr.N.Mugunthan 38

39. • Skeletal muscle L.S
• Skeletal muscle T.S
• Cardiac muscle L.S
• Smooth muscle
Summary
© Dr.N.Mugunthan 39

40. Exercise -1
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41. Exercise -2
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42. Exercise -3
© Dr.N.Mugunthan 42

43. © Dr.N.Mugunthan 43