rhomboid minor muscle, and levator scapulae muscle will bestudied. Dissection of the superficial back muscles should be
performed bilaterally:
Dissection Instructions
TRAPEZIUS MUSCLE [G 307; N 157; R Z12; C407]
I. Clean the surface of the lrapezius muscle (L. Impe-
zoida, an irregular four-sided figure) (Fig. 1.09). Do
not dimarb ab: mpaiar border of tbe trapeziu: made.
Observe the proximal attachment of the trapezius
muscle on the external occipital protuberance, the
nuchal ligament, and the spinous processes of verte-
lrae C7 to T12.
2. The trapezius muscle has three parts with distinctly
diflerent actions:
° Superior part of the trapezius muscle attaches to
the lateral one-third of the clavicle and it elevates
the scapula.
° Middle part of the trapezius muscle attaches to the
acromion and spine of the scapula and it retracts
the scapula.
° Inferior part of the trapezius muscle attaches near
the medial end of the spine of the scapula and it
depresses the scapula.
3. Reflect the trapezius muscle. Insert your fingers deep
to the lrapezius muscle, starting at the posterolateral
border of the muscle (medial to the inferior angle of
the scapula). Break the plane of loose connective tissue
between the trapezius muscle and the deeper muscles
of the back.
4. Use scissors to detach the trapezius muscle from its
poximal attachment on the spinous procaes and the
nuchal ligament (dashed line, Fig. 1.09). Start inferi-
crly and continue the cut superiorly as far as the exter-
nal occipital protuberance.
5. Use scisors to make a short transverse cut (2.5 cm)
across the superior end of the trapezius muscle to
detach it from the superior nuchal line. Spare the
gmmr acdpiml nerve, and do not cam-nd the mmrvcrse an
beyond the border qfrbe mrpeziau muck.
6. Use a scalpel to shave the trapezius muscle from its
distal attachments on the spine and acromion of the
stapula. Cut very close to the bone. Leave the trapez-
hs muscle attached to the clavicle and cervical Fascia.
7. Reflect the trapezius muscle superolaterally. Leave the
cervical Fascia attached along the superior border of
the trapefius muscle to act as a hinge.
8. Study the deep surface of the reflected trapezius mus-
de. Find the plexus ofnerves formed by the accesso-
ry nerve and lranches of the vmtral primary rami
of spinal nerves C3 and C4. The accessory nerve
[rovid motor innervation to the trapezius muscle;
the branches of nerves C3 and C4 are sensory (propri-
oception). The superficial branch of the transverse
cervical artery accompanies the nerves. Remove the
transverse cervical vein to clear the dissection field.
9. The accesory nerve (cranial nerve XI) passes through
the posterior triangle of the neck. Do not follow the
nerve into the posterior triangle at this time. The pos-
terior triangle will be dissected with the neck.
IATISSIMUS DORSI MUSCLE [G 307; N 157; R Z12; CW7]
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