1. Muscle Microanatomy
Department of Biology, WCU

2. Introduction Types 1. Skeletal Skeletal, smooth, cardiac
cover skeleton
Striations
voluntary control
rapid contractions

3. Introduction 2. Smooth walls of hollow organs no striations
involuntary control
slow contractions

4. Introduction 3. Cardiac involuntary control Striations
contractions slow but variable

5. Structural characteristics
Common features
1. Nucleated
2. Fibers
3. Myofilaments

6. Functional characteristics
1. Excitable
2. Contractible
3. Extensible
4. Elastic

7. Gross anatomy Layers 1. Epimysium 2. Perimysium 3. Endomysium
Muscle mm
Body cell µm

8. Microscopic anatomy Sarcolemma Sarcoplasm myofibril myoglobin
elaborate ER

9. Myofibril
rod-like filaments (80%)
sarcomeres

10. Sarcomere
Definition
A band
I band
H zone
M line

11. Sarcoplasmic Reticulum
SER
Terminal cisternae
Store and release Ca++

12. Triad
T system
T tubule (telegraph)

13. Comparative anatomy
1. Skeletal
Multinucleate
Long axis contraction

14. Comparative anatomy 2. Smooth 1 nucleus no striations only endomysium
no t-tubules
poorly developed SR

15. Comparative anatomy 2. Smooth occurs in 2 layers outer longitudinal
inner circular

16. Comparative anatomy 3. Cardiac muscle one or two nuclei striations
only endomysium
few SR
intercalated disks

17. Comparative anatomy 3. Cardiac muscle intercalated disks desmosomes
gap junctions