1. Muscle tissue
Specialized for contractility

2. Classification of muscle tissue
Functional classification based on neural control
Voluntary
Involuntary
Structural classification based on the presence of
striations
Striated
Non-striated
Striated
Non-striated

3. Types of muscle Skeletal muscle Cardiac muscle Smooth muscle
Voluntary & Striated
Hypertrophy only
Cardiac muscle
Involuntary & Striated
Smooth muscle
Involuntary & Non-striated
Hypertrophy and hyperplasia

4. Skeletal muscle fibers (cells)
Largest fiber type
Cylindrical
Unbranched
Heavy cross striations
Multiple, peripheral nuclei
Skeletal muscle fibers (cells)
Longitudinal sections
Cross sections

5. Skeletal muscle fibers
Fibers contain numerous longitudinally arrayed myofibrils composed of myofilaments (actin and myosin)
Myofibrils
Cross sections

6. Skeletal muscle fibers
Longitudinal sections
Cross sections
SER

7. Banding pattern Sarcomere Z-line to Z-line Contractile unit
Muscle fibers
Banding pattern
A band (dark) - Myosin and actin
I band (light) - Actin only
Z line - Alpha actinin
H band – Myosin only
Sarcomere
Z-line to Z-line
Contractile unit BV A I Z
Myofibrils I Z A
Myofilaments H
Sarcomere

8. Organization of myofilaments
Actin
Myosin
70,000x

9. Changes in bands during contraction
Sarcomeres shorten
Z-line interval narrows

10. Changes in bands during contraction
Sarcomeres shorten
Z-line interval narrows
H and I bands narrow

11. Changes in bands during contraction
Sarcomeres shorten
Z-line interval narrows
H and I bands narrow
A band is unchanged

12. Regulation of skeletal muscle contraction
T-tubule
Triads:
T-tubule (sarcolemma)
Terminal cisterns of SER (sarcoplasmic reticulum)
Ca+

13. Connective tissues of skeletal muscle
1. Segregate the muscle fibers into fascicles
2. Transmit the force of contraction to the point
of muscle insertion
Endomysium - reticular fibers plus the external (basal) lamina produced by the muscle fiber
Perimysium - dense connective tissue surrounding a group of fibers and dividing the muscle into fascicles
Epimysium - dense connective tissue surrounding the entire muscle, blends with the deep fascia and tendons

14. Connective tissues of skeletal muscleRF
Endomysium
Fiber
Epimysium
Perimysium

15. Neuromuscular junction
(Motor end plate)

16. Cardiac muscle Most restricted distribution (myocardium)
Cardiac muscle fibers
Intermediate size
Cylindrical fibers
Fibers branch, forming interwoven bundles
Single, centrally located nucleus
Moderate striations
Myofibrils and myofilaments similar to skeletal muscle
Highly vascular
Large numbers of mitochondria
Glycogen
Longitudinal section, 400x
Cross section, 1000x

17. Cardiac muscle fibers M
Nucleus M
Myofibrils M

18. Cardiac muscle - Intercalated discs
Unique to cardiac muscle
fibers
Composed of:
Adherent junctions
Gap junctions (ionic coupling)

19. Regulation of contraction
T tubules
No triads, reduced sarcoplasmic reticulum
Contraction regulated by calcium
Contraction spreads to adjacent cells due to current flow through gap junctions

20. Smooth muscle Organized into sheets forming much of the wall of
hollow organs and blood vessels
Smooth muscle fibers
Smallest fiber type
Spindle shaped
Single, centrally placed nucleus
Non-striated, no myofibrils
External lamina
Gap junctions
Hypertrophy & hyperplasia

21. Smooth muscle Longitudinal layers Circular layer Longitudinal section
Cross section
Circular layer
Longitudinal layers

22. Myofilament organization
Actin and myosin present
No myofibrils
Myofilaments arranged as
reticulum
Dense bodies in cytoplasm
Relaxed
Dense
body
Contracted
“Inchworm nuclei”

23. Coordination of contraction
Small fibers, T-tubules are absent (caveolae)
Sarcoplasmic reticulum is rudimentary
Ionic coupling via gap junctions
Contraction initiated by calcium release
Contraction occurs by sliding filament mechanism unique to smooth muscle
Caveolae
Desmo-
some
Gap junction
Dense
bodies
Nucleus
Smooth muscle fiber (EM)

24. Skeletal
Cardiac
Smooth