1. Major Muscles of the Upper Body

2. Different arrangements of fascicles

3. Arrangement of fascicles influences movement and power
Skeletal muscles can shorten by about 1/3 of their resting length
The more nearly parallel to the axis, the more they can shorten
This results in a larger distance of movement
The power depends on the total number of fibers
Stocky muscles (like bipennate vs parallel) have more fibers, therefore more powerful even though shorten very little

4. Interactions of Skeletal Muscles
Muscles can only pull, they can’t push
Actions must be “undone” by a different muscle
Muscles that produce opposite movements usually lie on opposite sides of a given joint

5. Interactions, continued
Agonist: prime mover, major responsibility for producing a specific movement
Antagonist: oppose or reverse a particular movement
Usually contract a little to prevent overshooting the mark or slow the agonist’s action near the end
Are being stretched or can remain relaxed when agonist works
Antagonists for one movement can be agonists for another

6. Synergists help prime movers
Add a little extra force to the same movement
Or reduce undesirable extra movements (e.g. making a fist without flexing at wrist)
Fixators: hold a bone firmly so agonist has a stable base on which to move a body part (e.g. fixing scapula when arm moves)

7. Naming skeletal muscles (examples)
Location: brachialis is in arm (brachium = arm)
Shape: deltoid is triangular (delta = triangle)
Size: minimus (smallest), longus (long), brevis (short)
Direction of fascicles and fibers: rectus (straight); transversus (right angle) and oblique (oblique) to midline
Number of origins: biceps (“two heads”), triceps (“three heads”), quadriceps (“four heads”)
Action: “flexor,” “extensor,” “adductor” or “abductor” appear in the name
Combinations of the above, e.g. extensor carpi radialis longus

8. Muscles of the Head and Neck
Scalp Muscle: epicranius
frontal belly
occipital belly
gala aponeurotica
Muscles of Facial Expression: insert on skin or another muscle
Muscles of Mastication (chewing): all have insertions on the mandible
Anterior Neck Muscles
Posterior Neck Muscles

9. 23

10. 24

11. Anterior

12. Anterior Chest Muscles

13. Posterior

14. Muscles moving the scapula
posterior

15. Rotator cuff supraspinatus, infraspinatus, subscapularis, teres minor

16. Anterior Arm

17. Forearm extensors (posterior)
Triceps brachii
Anconeus helps

18. Deep muscles of back

19. Deep muscles of the thorax: breathing
Intercostals
Short: rib to rib
Diaphragm
prime mover
of inspiration

20. Muscles of the abdominal wall

21. Muscles of the abdominal wall from the side