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Nine muscles cross the
shoulder joint and insert into the humerus
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Prime movers include:
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Pectoralis major – arm
flexion
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Latissimus dorsi and
posterior fibers of the deltoid – arm extension
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Middle fibers of the
deltoid – arm abduction
- Rotator cuff muscles – supraspinatus, infraspinatus, teres minor,
and subscapularis
- Function mainly to reinforce the capsule of the shoulder
- Secondarily act as synergists and fixators
- The coracobrachialis and teres major:
- Act as synergists
- Do not contribute to reinforcement of the shoulder joint