Muscles of the thorax that move the shoulder orig-
inate on the axial skeleton and insert on the clavicle
or scapula. Figure 6.17 illustrates and describes these
muscles.
M uscles o f th e th o ra x th a t m ove th e sh o u ld e r •
Figure 6.17
2 f
4
5
6
7
2
3
4
6
7
7
8
9
9
Levator scapulae
Trapezius
Clavicle
Pectoralis
minor
Humerus
Serratus
anterior
External
intercostal
Internal
intercostal
Levator scapulae
. »
Anterior deep view
Scapula
Serratus
anterior
Ribs
Anterior deeper view
Muscle
Origin
Insertion
Action
Muscles of the thorax that move the shoulder
Pectoralis minor
(pek'-tor-
A-lis;
pect-
= breast, chest,
thorax;
minor
= lesser)
Second through fifth,
third through fifth, or
second through fourth
ribs
Scapula
Abducts scapula and rotates it downward
(movement of glenoid cavity upward); elevates third
through fifth ribs during forced inhalation when
scapula is fixed
Serratus anterior
(ser-A-tus;
serratus
= saw-toothed;
anterior
= front)
Upper eight or nine ribs
Scapula
Abducts scapula and rotates it upward (movement
of glenoid cavity downward); elevates ribs when
scapula is fixed; known as "boxer's muscle" because
it is important in horizontal arm movements such as
punching and pushing
Trapezius
(tra-PE-ze-us;
trapeze-
= trapezoid-shaped)
Occipital bone and spines
of seventh cervical and all
thoracic vertebrae
Clavicle and
scapula
Superior fibers elevate scapula; middle fibers
adduct scapula; inferior fibers depress and upward
rotate scapula; superior and inferior fibers together
rotate scapula upward; stabilizes scapula
Levator scapulae
(le-VA-tor
SKA-pu-le;
levator
= to raise;
scapulae
= of the scapula)
Upper four cervical
vertebrae
Scapula
Elevates and adducts scapula and rotates it
downward
176 CHAPTER 6
The Muscular System
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