deep muscles of the back 10

deep muscles of the back 10

 

~r. menury me uu-ee O0lI.II1ll1! or me erector spmae

muscle (L. erector, one who erects) (Fig. 1.10):

' Spinalis muscle forms the medial column of the

erector spinae muscle. The inferior attachments of

the spinalis muscle are on spinous proceses. Its

superior attachments are also on spinous proceses.

The spinalis muscle is present at lumbar, thoracic

and cervical vertebral levels.

' Longissimus muscle (L. bngissimus, the longest) is

the intermediate column of the erector spinae mus-

cle. Its inferior attachment is on the sacrum and its

superior attachments are the transverse proceses

of the thoracic and cervical vertebrae. Note that its

most superior portion, the longissimus capitis

muscle, attaches to the mastoid proc of the tem-

poral bone.

' lliooostnlis muscle is the lateral column of the

erector spinae muscle. Its inferior attachment is the

ilium (iliac crest) and its superior attachments are

on ribs (L. mm, rib).

5. All three columns of the erector spinae muscle extend

the vertebral column when both sides work together.

If only one side is active, the erector spinae muscle

bends the vertebral column laterally toward the side

that is active.

TRANSVERSOSPINAI. GROUP OF MUSCLES [G 31 Z; N 159;

R Z1 5; C 41 1]

The mmsversospinal group of muscles '5 located deep

to the erector spinae muscle. The muscles in the transver-

sospinal group attach to transverse proceses and spinous

The order of dissection will be as follows: the deep muscles of
the posterior neck (splenius and semispinalis capitis) will be
studied. The erector spinae muscle will be dissected and its com-
ponent parts will be identified

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Dissection Instructions
SPLENIUS MUSCLE [G 309; N ‘I57; R Z12; C 408]
1. Identify the splenius muscle (Gr. splmion, bandage).
The splenius muscle lies deep to the trapefius muscle
and its fibers course obliquely across the neck. The
troximal attachment of the splenius muscle is the
nuchal ligament and the spinous processes of verte-
lrae C7 to T6.
2. The splenius muscle has two parts that are named
according to their distal attachments:
° Splenius capitis muscle (L. mput, head) is
attached to the mastoid process of the temporal
bone and the superior nuchal line of the occipital
bone.
° Splenius oervicis muscle  cervix, neck) is
attached to the transverse processes of the verte-
lrae Cl to C4.
3. Detach the splenius muscle from the nuchal ligament
and the spinous processes of vertebrae C7 to T6.
4. Reflect the muscle laterally, leaving its distal attach-
ments undisturbed.

 

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deep muscles of the back 9

deep muscles of the back

 

IHOMDOID MAJOR AND RHOMDOID IINOR MUSCLES [G

II; N 170; R 212;C 407]

1. Clean the surface and borders of the ihomboid

(rhomboileus) minor muscle and the ihomboid

major muscle (Gr. rbornbos, shaped like a kite). The

plane of separation between the rhomboid muscles

may not be obvious.

2. The  attachments of the rhomboid minor

muscle are the nuchal ligament and the spinous

processes ofvertehrrae C7 and Tl. The distal attach-

ment of the rhomboid minor muscle is the medial bor-

der of the scapula near the spine.

3. The  attachments of the rhomboid major

muscle are the spinous processes of vertebrae T2 to

T5. The distal attachment of the rhomboid major

muscle is the medial border of the scapula inferior to

the spine.

4. The rhomboid muscles retract the scapula, rotate the

scapula to depress the glenoid cavity, and hold the

stapula close to the thoracic wall.

5. Reflect the rhomboid muscles. Beginning at the infe-

rior angle of the scapula, insert your fingers deep to

the rhomboid major muscle and separate it fi'om deep-

5' muscles.

6. Use scissors no detach the rhomboid major muscle

fiom its  attachments. Continue the cut supe-

riorly and detach the rhomboid minor muscle fiom its

proximal attachments. Reflect these two muscles later-

ally.

7. Examine the deep surface of the rhomboid muscles.

Use blunt disection to find the dorsal scapular

nerve and dorsal scapular vessels. Remove the dor-

sal scapular vein to clear the dissection field. The dor-

sal scapular nerve and artery course parallel to the

medial border of the scapula. The dorsal scapular

artery may branch directly from the subclavian artery,

a' it may arise from the transverse cervical artery in

which case it is also called the deqa branch of the

transverse cervical artery.

LEVATOR SCAPULAE MUSCLE [G 308: N ‘I67; R Z14; C 407]

1. Identify the levamr scapulae muscle (L. levers, to

raise).

2. Note that the proximal attachments of the levator

rapulae muscle are the transverse proceses of the

upper four cervical vertebrae. Do not disect its prox-

inal attachments.

3. The distal attachment of the levator smpulae muscle is

the superior angle of the scapula. The levator scapulae

muscle can be seen only near its distal attachment.

4. The dorsal scapular nerve and artery supply the leva-

D!‘ scapulae muscle. The levator scapulae muscle ele-

vates the scapula and rotates the scapula to depr the

glenoid cavity.

--------------------------------

movements that occur between the scapula and the thoracicwall. Use an illustration to observe the origin of the transverse
cervical artery and the dorsal scapular artery. Observe two trian-
gles mmiamd with the latiwimus dorsi muscle: The triangle of
auscultation and the lumbar triangle (of Petit) (Fig. 1.09).
-----------------------------

INTERMEDIATE MUSCLES OE Tl-IE
BACK [6 soa; N 167; R 219; c 408]
Dissection Instructions
The intermediate muscles of the Incl: are the serratus
posterior superior muscle and the sa-ratus posterior
inferior muscle. These are very thin muscles, which may
be accidentally reflected with the rhomboid muscles or the
latisdmus dorsi muscle. If you do not see the serratus pos-
terior muscles, look for them on the deep surface of the
rhomboid muscles or the latisimus dorsi muscle.
1. The proximal attachments of the sa-ratus posterior
superior muscle are the nuchal ligament and the
spinous processes of vertebrae C7 to T3. Its distal
attachments are the superior borders of ribs 2 to 4, lat-
a‘al to their angles.
2. The proximal attachments of the sa-ratus posterior
inferior muscle are the spinous processes of vertebrae
T11 to L2. Its distal attachments are the inferior bor-
ders ofribs 8 to 12, lateral to their angles.
3. The serratus posterior muscles are respiratory mus-
des, and they are innervated by interoostal nerves.
4. Detach both serratus posterior muscles from the spin-
ous processes. Reflect the muscles laterally, leaving
them attached to the ribs.
DEEP MUSCLES OE Tl-IE BACK
Before you dissect. . .
The (hep muscles of the back act on d'1e vertebral column.
There are many deep muscles of d'1e back (Fig. 1.10) and only a
few will be dissected: splenius muscle, semispinalis capitis
muscle, and sector spinae muscle.All of d'1e deep muscles of
d'1e back are innervated by dorsal primary rami of spinal nerves.


 

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SUPERFICIAL MUSCLES OF THE BACK 8

SUPERFICIAL MUSCLES OF THE BACK

rhomboid minor muscle, and levator scapulae muscle will be
studied. 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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SUPERFICIAL MUSCLES OF THE BACK 7

SUPERFICIAL MUSCLES OF THE BACK

Dissection Instructions

SKIN INCISIONS

1. Refer to Figure 1.07.

2. Use a scalpel to make a vertical skin incision in the

midline fiom the external occipital protuberance (X)

to the tip of the coccyx  The skin is approximately

6-mm-thick in this region.

3. Make an incision from S to the midaxillary line (T).

This incision should pas approximately 3 cm inferior

to the iliac crest.

4. At the level of the inferior angle of the scapula, make

a transverse skin incision from the midline (U) to the

midaxillary line  To facilitate skinning, make a par-

allel transverse incision above and below this one.

5. Make a transverse dcin incision from R to B, superior

to the scapula and superior to the acromion. Extend

this incision to point F, approximately halfway down

the arm.

6. At point F, make an incision around the anterior and

posterior surfaces of the arm, meeting on the medial

s'de (G). If the upper limb has been disected previ-

cusly, this incision has already been made.

7. Make a skin incision that begins at G on the medial

surface of the arm and extends superiorly to the axilla.

Extend this incision in feriorly along the lateral surface

of the trunk, through V to T.

3. Make a transverse skin incision from the external

occipital protuberance (X) laterally to the base of the

rmstoid proces (M).

9. Make an incision along the lateral surface of the neck

and superior border of the trapezius muscle (M to B).

10. Remove the skin from medial to lateral. Detach the

skin and place it in the tisue container.

 SUPERHCIAI. FASCIA

1. In the superficial fascia, locate the occipital artery

and the greater occipital nerve (Fig. 1.08). First, find

the occipital arteryand then look on its medial side for

the greater occipital nerve. The greater occipital nerve

is the dorsal primary ramus of spinal nerve C2. The

greater occipital nerve pierces the trapezius muscle

approximately 3 cm inferolateral to the external

occipital protuberance. The deep fascia in this area

is very dense and tough. Therefore, it may be difficult

to find the greater occipital nerve, even though it is

large. [G I17; N 171; R 212; C 414]

2. Read a description of the dorsal primary ramus of a

qainal nerve. The posterior cutaneous branches of

the dorsal primary rami pierce the trapezius muscle or

latissimus dorsi muscle to enter the superficial fascia

(Fig. 1.08). To save time, make no deliberate efiort to

display posterior cutaneous branches of the dorsal pri-

mary rami. Ii 20; N 187; R Z04]

3. Reflect the superficial fascia of the back from medial

In lateral. Detach the superficial fascia by cutting it

along the skin incision lines and place it in the tissue

container

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4. In the neck, reflect the superficial fascia only as fir lat-

aally as the superior border of the  muscle.

Domntrut lb: deepfnria along tbenipniorbordcr aftb:

tmpeziiu made. The aocaory nerve is superficial at

this location and it is in danger of  cut.

After you dissect . . .

Review the branching pattern of a typical spinal nerve and

understand that cutaneous branches of the dorsal primary rami

innervate the skin of the back. Study a dermatome chart and

become familiar with the concept of segmental innervation. [G

B1; N 151; C404]

SUPERFICIAL MUSCLES OF Tl-I E

BAC K

Before you dissect . . .

The slperficial muscles of the bad: are also called the poste-

n'or thoraooappendicular muscles because they attach to the

axial skeleton and the upper limb. There are five superficial

muscles of d1e back: trapezius, latissimus dorsi, rhomboid

major, rhomboid minor, and levator scapulae.

The order of dissection will be as follows: the superficial sur-

filce of the trapezius muscle will be cleaned. The trapezius mus-

de will be examined and reflected. The latksimus dorsi muscle

will be studied and reflected. The rhomboid major muscle,

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skeleton of the back 6

skeleton of the back

.

lumbar vertebrae differ from thoracic vertebrae in the fol-

lowing ways (Fig. 1.05): lumbar vertebrae have larger bodis,

broad spinous process that project posteriorly, and they do not

have articular facets for ribs. On a skeleton, observe the lumbar

vertebrae and notice that their spins do not overlap like the

spines of thoracic vertebrae. [6 Z89; N 148; R 1%; C 426]

The sacrum is formed by five fused vertebrae and it does not

have identifiable spins or transverse process. On the dorsal

surface of the sacrum, identify (Fig. 1.06): [G Z93; N 150; ll ‘I87;

C418]

° Median sacral crest

° Posterior (dorsal) sacral foramina

' Sacral hiatus

The ooecyx is a small triangular bone formed by four rudi-

mentary coocygeal vertebrae that are fused together (Fig. 1.06).

SKIN AND SUPERFICIAL FASCIA

Before you dissect . . .

The order of disection will be as follows: the skin will be

removed from the back, posterior surface of the neck, and pos-

terior surface of the proximal upper limb. Posterior cutaneous

nervs will be studied. The superficial fscia will then be

removed 

 

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skeleton of the back 5

skeleton of the back

larger vertebral foramina, shorter spinous proceses that bifur-

cate at the tip, and transverse processes that contain a foramen

transversarium. On an articulated skeleton, identifir the follow-

ing features common to all cervical vertebrae: [G Z84; N 15;

R 135; C Q18]

° Transverse process

° Foramen transversarium

° Spinous pros

On a skeleton, observe the following features of individual

cervical vertebrae:

° Atlas (C1)- does not have a

° Axis (C2) - has the dens, which is the body of C1 that has

become fused to C2 during development.

° Wertebra prominens (C7) - has the most prominent spinous

proc in the cervical region, hence its name

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° Transverse pmcess (2)
' Tramverse costal facet
' Spinous process
' Articular processes - superior and inferior
' Vertebral notches - superior and inferior
' Costa] fiicets - superior and inferior
The spinous process of a thoracic vertebra is long, slender,
and directed inferiorly over the spinous proc of the vertebra
that is inferior to it. Articulation with ribs is a unique character-
ktic of thoracic vertebrae. The head of a rib articulates with the
bodies of two adjacent vertebrae (Fig. 1.04). The tubercle of a
rib articulates with the transverse costal facet of the thoracic ver-
tebra of the same number (i.e., the tubercle of rib 5 articultes
with the transverse costal facet of vertebra T5). An imerverte-
bral dis]: and the articular processes unite two adjacent verte-
brae. The vertebral notches of two adjacent vertebrae combine
to form an intervertebral foramen. A spinal nerve pases
through the intervertebral foramen.
Cerviml vertebrae differ from thoracic vertebrae in the fol-
lowing ways (F ig. 1.05): cervical vertebrae have smaller bodies,

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The back

The back

The back region contains the superficial muscles of the back

 (posterior thoracoappendicular muscles), the intermediate

muscles of the back, and the deep muscles of the back. All of

these muscles attach to the vertebral column. The vertebral col-

umn serves the dual purpose of forming the axis of     the body and

providing a protective bony covering for the spinal cord.

Surface  Anatomy

The surface anatomy of this region may be studied on a living

subject or on the cadaver. In the cadaver, fixation may make it

difficult to distinguish  bone from well-preserved  soft  tissues.

Turn the cadaver to the prone position (face down) and palpate

the following structures (Fig. 1.01): [N 145]

The deep muscles of the back act on the vertebral column.
                       Replace  the  superficial  muscles  of  the  back  in  their  correct                                                    There are many deep muscles of the back (Fig. 1.10) and only a
                       anatomical positions. Use the dissected specimen to review the                                                           few will be dissected: splenius  muscle,  semispinalis  capitis
                       proximal attachment, distal attachment, action, innervation, and                                                         muscle, and erector spinae muscle. All of the deep muscles of
                       blood supply of each muscle that you have dissected. Review the                                                          the back are innervated by dorsal primary rami of spinal nerves. 

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