1. Ch 9: Skeletal Muscle Tissue and Organization
main objectives:
Describe the distinguishing characteristics of the different muscle tissues
Discuss the organization of skeletal muscle
Explain the micro-anatomy of a skeletal muscle fiber
Describe the fascicle arrangement in different types of muscle
Review general muscle terminology

2. Muscle tissue vs. Muscle as an organ
One of the 4 primary tissue types
How many subtypes?
Made up of _____ tissue types.
> 700 skeletal muscles
Word roots:
sarco
mys

3. Function of Skeletal Muscles
Skeletal movement
Posture and body position
Support of soft tissues
Guarding of entrances & exits
Maintenance of body temperature

4. Gross Anatomy
Each skeletal muscle is wrapped by 3 concentric layers of
connective tissue.

5. Epi-, Peri-, and Endomysium
Are interwoven - Go over into tendon
Distinguish between:
Tendon
Aponeurosis
Ligament
Function:
Protection
Blood supply
Innervation
Fig 9-1

6. Nerve and Blood Vessel Supply
Skeletal muscles are rich in nerves and blood vessels
Chemical communication at Synapsis (neuromuscular junction)
Synaptic terminal of axon meets motor end plate of muscle cell
Coiled capillaries are able to adapt to changes in length of muscle fiber
Fig 9-2

7. Microanatomy of Skeletal Muscle Fibers
Some vocabulary:
Skeletal muscle fiber or myofiber
Sarcolemma
Sarcoplasm
Sarcoplasmic reticulum
Myofibril
Myofilaments
Fig 9-3

8. Myofiber ( 100µm) Myofibrils ( 1-2 µm) Myofilaments
Actin & Myosin

9. Sarcomeres
Thick and Thin Filaments are organized in repeating functional units = ______
Each myofibril has linear arrangement of ~ 10,000 sarcomers
Banded appearance (striation) due to arrangement of thick and thin filaments
Interaction of thick and thin filaments responsible for skeletal muscle fiber contraction

10. Sarcomere Structure
Z - line
I - band
= LIght band
A- band
= dArk band

11. Thin Filament: Actin
F-actin
G-actin

12. Thick Filament: Myosin

13. Development of Myofibers from Myoblasts
Some Myoblasts do not fuse satelite cells in endomysium
regeneration of muscle

14. Motor Units
= All muscle fibers that are controlled by a single motor neuron
The lower the ratio of muscle fibers to neurons, the more precise the movement can be!
Few cases 1: 1 relationship. Where?
Most cases: many muscle fibers (up to 2,000) : 1 motor neuron. Where?
Fig 9-12

15. Muscle Control
Muscle tone = Resting tension of skeletal muscles (continuous contraction of some motor units to maintain some muscle tension)
Recruitment or Multiple motor unit summation
Maximal tension production: ?

16. Muscle Hypertrophy vs. Atrophy
Hypertrophy due to anaerobic exercise
Leads to increased muscle size - how?
Atrophy if supply of myofilaments exceeds demand. Muscle fibers become smaller and weaker.
Eventual death of muscle fibers is irreversible! Importance of Physical Therapy

17. Three Types of Muscle Fibers
1) Fast (or White) Fibers
Fast contraction after nervous stimulation
Large diameter
large glycogen reserve
few mitochondria
densely packed myofibrils
Fatigue fast due to mainly anaerobic respiration

18. 2) Slow (or Red) Fibers
Slower but continuous contraction for extended periods
Smaller diameter (~ half)
contain myoglobin
more capillaries
more mitochondria
Do not fatigue as fast due to ?
Fig 9-13

19. 3) Intermediate Fibers Have attributes inbetween fast and slow types
Most skeletal muscles contain mixture of fiber types. Proportion of fast to slow depends on ___________?
One motor unit only contains one fiber type
Eye, hand: ____ fibers dominate
Back, calf: ____ fibers dominate

20. Organization of Skeletal Muscle Fibers
Effect of individual muscle contraction determined by:
arrangement of muscle fibers
way of attachment to skeletal system
Bundles of muscle fibers =
Muscle fibers within 1 fascicle are parallel
4 types of fascicle organization

21. Parallel Muscels Majority Spindle shaped with cord-like tendons
Some flat bands with broad _____ on each end
Examples: ?

22. Convergent muscels Broad origin, pointed insertion
Direction of pull can be varied: versatility!!
Example

23. Pennate Muscles: Unipennate
One or more tendons run though muscle body
Fascicles in oblique angle to tendon
Can generate more tension
Example

24. Pennate Muscles: Bipennate & Multipennate
Example
Example

25. Circular Muscles = Sphincters Concentric fibers adjust opening
Examples: orbicularis occuli and oris

26. Muscle Terminology Origin stationary Insertion moves
Possible: multiple origins

27. Types of Actions flexion, extension adduction, abduction
elevation, depression
rotation, circumduction
pronation, supination
etc

28. Grouping of Muscles according to Primary Action
Agonist = Prime Mover
Antagonist (action opposes agonist)
Synergists = Assistants of prime mover

29. Naming of skeletal Muscles
Orientation of fibers
Size & shape
Location
Action
Origin & / or insertion
Specific features
Use muscle name to help identify its location, appearance and function!

30. The End