Muscles of the neck and back are responsible for
movement of the spine. These include the erector spinae,
sternocleidomastoid, quadratus lumborum, and psoas ma-
jor. The erector spinae is the largest muscular mass of the
back and consists of three groups of overlapping muscles:
the iliocostalis group, longissimus group, and spinalis
group. These groups are illustrated in Figure 6.19. See
Figure 6.13b for an illustration of the sternocleidomastoid,
and see Figure 6.23 for illustrations of the quadratus lum-
borum and psoas major.
M uscles o f th e neck and back th a t m ove th e sp in e • Figure 6.19
3
4
5
8
9
Longissimus group
(intermediate)
Iliocostalis group
(lateral)
Spinalis group
(medial)
Deep view
Muscle
Origin
Insertion
Action
Muscles of the neck and back that move the spine
Erector spinae
(e-REK-tor
SPI-ne; iliocostalis group,
longissimus group, and
spinalis group)
All ribs plus cervical,
thoracic, and lumbar
vertebrae
Occipital bone, temporal
bone, ribs, and vertebrae
Extends head; extends and laterally flexes
vertebral column
Sternocleidomastoid
(ster'-no-klT-do-MAS-toid)
(see Figure 6.13b)
Sternum and clavicle
Temporal bone
Contractions of both muscles flex cervical part
of vertebral column and flex head; contraction
of one muscle rotates head toward side
opposite contracting muscle
Quadratus lumborum
(kwod-RA-tus lum-BOR-um)
(see Figure 6.23)
Ilium
Twelfth rib and upper four
lumbar vertebrae
Contractions of both muscles extend lumbar
part of vertebral column; contraction of one
muscle flexes lumbar part of vertebral column
Psoas major
(SO-as)
(see Figure 6.23)
Lumbar vertebrae
Femur
Flexes vertebral column; flexes and rotates
thigh laterally at hip joint
178 CHAPTER 6
The Muscular System
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