D. J. (Daniel John) Cunningham.

Cunningham's manual of practical anatomy (Volume 1) online

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remainder of the dissection can be undertaken on the second
day.

Dissection. Reflection of the Skin. The following incisions
are necessary : i. From the tip of the coccyx, at the lower end
of the vertebral column, upwards, along the median line of the
body, to the spine of the seventh cervical vertebra. 2. From
the upper end of i transversely, to the tip of the acromion of the
scapula. 3. From the lower extremity of the median incision
in a curved direction laterally and forwards, along the crest of
the ilium, to within two inches of the anterior superior iliac spine.
4. An oblique incision from the spine of the first lumbar vertebra,
upwards and laterally, to the posterior fold of the axilla, and along
the latter to the arm. The two large flaps (17 and 18, Fig. 25)
which are now mapped out upon the back must be carefully
raised from the subjacent fatty tissue. Reflect the upper
triangular flap first, and then the lower flap.

Panniculus Adiposus (Superficial Fascia). In subjects
which have been allowed to lie for some time on the back
the superficial fascia is usually more or less infiltrated with
fluid which has gravitated into its meshes ; otherwise it has
the ordinary characters of superficial fascia (p. 1 1 ).



DISSECTION OF THE BACK 51

Dissection. When searching for the cutaneous nerves cut
boldly down through the superficial fascia, in the direction in
which the nerves run (Fig. 26), until the plane is reached at
which the superficial and deep fascia blend. It is there that the
main trunks are to be found, and in a well-injected subject the
cutaneous arteries will serve as guides. A more rapid way of
finding the cutaneous nerves in this region is to reflect the super-
ficial and deep fascia laterally, from the vertebral spines, in one
layer ; the nerves are then found as they issue from the muscles.
This plan, however, should be adopted only by the senior student.

Nervi Cutanei et Vasa Cutanea (Cutaneous Nerves and
Vessels). The cutaneous nerves of the back are derived from
the posterior rami of the spinal nerves. As the posterior
rami pass backwards, they subdivide into medial and
lateral divisions. Both divisions supply twigs to the muscles
amongst which they lie ; but one or the other also contains
some sensory fibres which come to the surface, in the shape
of a cutaneous nerve, to supply the skin.

In the thoracic region the upper six or seven cutaneous
nerves are the terminations of the medial divisions of the
posterior rami of the thoracic nerves. They become super-
ficial close to the vertebral spines, and are to be sought
for near the median plane. It is not uncommon to find one
or more of them piercing the trapezius, one or two inches
lateral to the line of emergence of the others. The branch
which comes from the second thoracic nerve is the largest of
the series ; and it may be traced laterally, across the spine of
the scapula, towards the shoulder. The lower five or six
cutaneous nerves in the thoracic region are the terminal twigs of
the lateral divisions of the posterior rami of the thoracic
nerves ; and, consequently, they must be looked for at a
short distance from the middle line of the back. The upper
nerves of this group reach the surface after piercing the
latissimus dorsi muscle on the line of the angles of the ribs.
The lower nerves of the group pierce the lumbo-dorsal fascia
at the lateral margin of the sacrospinalis muscle. In every
case the cutaneous branches derived from the thoracic nerves
turn laterally, in the superficial fascia, and may be traced for
a varying distance in that direction.

It is important to note that the area of skin supplied by
each of these cutaneous nerves is placed at a lower level
than the origin of the posterior ramus from which it arises.

In the lumbar region three cutaneous nerves reach the
surface after piercing the lumbo-dorsal fascia at the lateral

i 4 a



THE SUPERIOR EXTREMITY



margin of the sacrospinalis muscle, a short distance above the
ilium. They are the terminal twigs of the lateral divisions
of the posterior rami of the upper three lumbar spinal nerves ;



Greater occipital nerve

Third occipital nerve

Sterno-mastoid

Lesser occipital nerve

Trapezi



Deltoid



Infra-
spinatus

Teres major

Rhomboideus
major

Triangular
space



Latissimus dorsi



Lateral divisions of
posterior rami of
lumbar nerv




Semispinalis capitis (O.T. complexus)

Splenius capitis
Cervical nerves to trapezius
Accessory nerve

. Ascending br. of transverse cervical arter
Levator scapulae

Descending br. of trs.
cervical artery and dorsal
scapulae nerve
Rhomboideus minor



Trapezius
(reflected)

Rhomboideus
major

Teres major



Serratus anterior



Serratus posterior inferior
Latissimus dorsi (cut)
-External oblique muscle
Trigonum lumbale (Petiti)

Gluteeus medius

Glutaeus maximus

I

FIG. 26. Dissection of the Superficial Muscles and Nerves of the Back.

and they differ from the nerves above, inasmuch as they turn
downwards over the crest of the ilium to supply the skin of
the gluteal region (Fig. 26).

The cutaneous arteries which accompany the cutaneous
nerves of the back are derived from the posterior branches
of the intercostal and lumbar arteries.



DISSECTION OF THE BACK



53



Muscles connecting the Limb to the Dorsal Aspect of the
Trunk. This group consists of five muscles, and they are
arranged in two strata. Two form the superficial stratum, viz.,
the trapezius and the latissimus dorsi. Both are broad, flat
muscles which cover the greater part of the dorsal aspect of
the trunk, from the occiput above to the ilium below. The
trapezius lies over the back of the neck and the thorax.
The latissimus dorsi is placed lower down. The deeper
stratum of muscles, composed of the levator scapulae and the
two rhomboid muscles, is under cover of the trapezius.



Semispinalis capitis
Rectus capitis posterior mino
Rectus capitis posterior major



Trapezius



Obliquus capitis superior




terno-cleido-mastoid
Splenius capitis



Rectus capitis lateralis

Rectus capitis anter

Longus capiti



Superior constrictor of pharynx.



FIG. 27. Muscle- Attachments to the Occipital Bone.



Dissection. After the cutaneous nerves and vessels have been
displayed and followed to their terminations, clean away the
remains of the fatty superficial fascia in the area of the trapezius,
but do not injure the deep fascia or the cutaneous nerves ; then
proceed to clean the trapezius, which is the most superficial
muscle of the back. The trapezius belongs only in part to the
dissector of the upper extremity. The portion of it which lies
above the prominent spine of the seventh cervical vertebra is the
property of the dissector of the head and neck, and must be
dissected by him. The two dissectors should work in conjunc-
tion with each other ; and when the entire muscle is exposed,
each should give the other an opportunity of studying it in its
entirety.

If the dissection is being made on the right side, place the arm
close to the trunk and drag the scapula forwards over the end of
the block which supports the thorax. Cut through the deep



54 THE SUPERIOR EXTREMITY

fascia from the seventh cervical spine to the acromion ; the
incision will correspond with the direction of the fibres of the
muscle at the level selected. Work gradually downwards, raising
the fascia in a continuous layer from the surface of the muscle.
Always carry the scalpel in the direction of the muscle fibres,
and take care to leave none of the fascia on the surface of the
muscle. As the direction of the muscle fibres changes, alter the
position of the arm to keep the fibres which are being cleaned on
the stretch. In the case of the left trapezius, the preliminary
incision through the fascia must be made along the lower margin
of the muscle, and the surface of the muscle must be cleaned,
from below upwards, to the level of the seventh cervical vertebra.
As the deep fascia is removed from the trapezius, and indeed
throughout the whole dissection of the back, the cutaneous
nerves must be carefully preserved, in order that the dissector
of the head and neck may have an opportunity of establishing
their continuity with the trunks from which they arise.

M. Trapezius. The trapezius is a flat, triangular muscle,
which lies, in its entire extent, immediately subjacent to the




FIG. 28. Upper Surface of the Right Clavicle.

deep fascia. It has a very long origin, which extends along
the median plane, from the occiput above to the level of the
last thoracic vertebra below. It arises from (i) the medial
third or less of the superior nuchal line of the occipital bone
and the external occipital protuberance ; (2) the ligamentum
nuchae and the spine of the seventh cervical vertebra ; (3) the
tips of the spines of all the thoracic vertebrae, as well as the
supraspinous ligaments which bridge across the intervals
between them (Figs. 26, 27).

In the lower cervical and upper thoracic regions the tendinous fibres by
which the muscle arises lengthen out so as to form a flat tendon, which,
taken in conjunction with the corresponding aponeurosis of the opposite
side, exhibits an oval outline.

As the fibres of the trapezius pass laterally they converge
to their insertions into the two bones of the shoulder-girdle.
The occipital and upper cervical fibres incline downwards, and,



DISSECTION OF THE BACK 55

turning forwards over the shoulder, are inserted into the
posterior border of the lateral third of the clavicle (Fig. 28);
the lower cervical and upper thoracic fibres pass more or less
transversely to gain an insertion into the medial border of
the acromion and the upper margin of the posterior border
of the spine of the scapula ; while the lower thoracic fibres are
directed upwards and, at the vertebral border of the scapula,
end in a flat, triangular tendon, which plays over the smooth
surface at the apex of the scapular spine, and is inserted
into a rough tubercle on the spine immediately beyond that
surface (Fig. 38, p. 83). To facilitate the movement of the
tendon upon the bone a small bursa mucosa is interposed
between them.

The trapezius is supplied by the accessory nerve and by
twigs from the third and fourth cervical nerves. It is an
elevator and depressor of the shoulder ; and a rotator and
adductor of the scapula.

Dissection. The latissimus dorsi is now to be dissected. It
is a difficult muscle to clean, not only on account of the varying
direction of its fibres, but also because its upper part is generally
very thin, and its upper border ill-defined. Near the spines of
the vertebrae its upper portion is overlapped by the trapezius, but
in its greater part the muscle is subcutaneous. Both the super-
ficial and the deep fascia should be raised at the same time from
its surface, and its fibres may be stretched by raising the arm
and folding it under the neck.

On the right side cut through the fascia along the upper border
of the muscle from the point where that margin disappears under
the trapezius to the posterior fold of the axilla, and work down-
wards. Define carefully the attachment to the superficial layer
of the lumbo-dorsal fascia. Clean that fascia, but do not injure it ;
it is the property of the dissector of the head and neck. Next
define the attachment of the lower end of the muscle to the crest
of the ilium ; and when the lower part of the lateral border of the
muscle is reached, clean the slips of the latissimus which are
attached to the lowest three or four ribs, and clean also the slips
of the external oblique muscle of the abdomen which inter-
digitate with the costal slips of the latissimus dorsi.

On the left side cut through the fascia from the crest of the
ilium to the posterior fold of the axilla, and work medially and
upwards ; and when the main part of the muscle has been cleaned,
return to the lower part of the lateral border and display the
costal attachments of the muscle and the interdigitations of the
external oblique.

After the costal slips of the muscle have been defined, evert
the upper margin of the muscle, as it crosses the inferior angle of
the scapula, to display the slip of fibres which springs from that
angle and joins the deep aspect of the upper border of the muscle ;
it is apt to be mistaken for a piece of the teres major upon which
it lies,
i 4c



THE SUPERIOR EXTREMITY



M. Latissimus Dorsi. The latissimus dorsi is a wide, flat
muscle, which covers the back from the level of the sixth
thoracic vertebra down to the crest of the ilium (Fig. 26, p. 52).
It arises (i) from the tips of the spinous processes of the
lower six thoracic vertebrae and the supraspinous ligaments in
connection with them; (2) from the superficial lamella of
the lumbo-dorsal fascia (Fig. 26) ; (3) by a thin tendinous origin
from a small extent of the outer lip of the crest of the ilium, in




FIG. 29. Diagram of the Lumbo-dorsal Fascia.

6. Fascia transversalis.

7. Sacrospinalis.

8. Quadratus lumborum

9. Psoas major.



1. Serratus posterior inferior.

2. Latissimus dorsi.

3. Transversus abdominis.

4. Obliquus internus.

5. Obliquus externus.



front of the lumbo-dorsal fascia (Fig. 26, p. 52); (4) by three
or four digitations from the lower three or four ribs; and (5)
by a fleshy slip from the dorsal aspect of the inferior angle
of the scapula (Fig. 38, p. 83). By means of its origin from
the posterior lamella of lumbo-dorsal fascia, it attains an in-
direct attachment to the spines of the lumbar and upper sacral
vertebrae, and also to the posterior part of the crest of the
ilium. The costal slips of origin interdigitate with the lower
digitations of the external oblique muscle of the abdominal
wall.

The fibres of the latissimus dorsi converge rapidly as



DISSECTION OF THE BACK 57

they approach the lower part of the scapula. The highest
fibres pass almost horizontally towards that point ; the lowest
fibres ascend almost vertically ; whilst the intermediate
fibres show varying degrees of obliquity. As a result of the
convergence of fibres, the muscle is greatly reduced in width ;
and it sweeps over the inferior angle of the scapula in the
form of a thick, fleshy band, which winds round the lower
margin of the teres major muscle and terminates in a
narrow, flat tendon, which is inserted into the floor of the
intertubercular sulcus of the humerus (Fig. 45, p. 107). The
insertion cannot be studied at present, but will be seen later.
With the teres major muscle, the latissimus dorsi forms the
posterior fold of the axilla. At first it is placed on the dorsal
aspect of the teres major, then it is folded round its lower
border, and finally it is inserted in front of it. To the
peculiar relationship of the two muscles is due the full,
rounded appearance of the posterior axillary fold.

The latissimus dorsi is supplied by the thoraco-dorsal nerve.
It is an adductor, retractor, and medial rotator of the upper
extremity.

Two Inter-muscular Spaces. (i) A triangular space
mapped out by the inferior border of the trapezius, the superior
border of the latissimus dorsi, and the base of the scapula,
should now be noticed (Fig. 26, p. 52). Within the limits of
that triangle a small portion of the rhomboideus major can be
seen, and also a varying amount of the wall of the thorax a
part of the sixth intercostal space and the borders of the ribs
which bound it above and below. It is well to note that
this is the only part of the thoracic wall on the posterior
aspect of the trunk which is not covered by muscles. (2)
Between the last rib and the crest of the ilium the anterior
border of the latissimus dorsi generally overlaps the
posterior border of the external oblique muscle of the
abdominal wall. Sometimes, however, a narrow triangular
interval exists between the two muscles, in which is seen a
small part of the internal oblique muscle. That space is
termed the trigonum lumbale (Petiti] (Fig. 26, p. 52). It is a
weak part of the wall of the abdomen, and occasionally some
of the contents of the abdomen are protruded through it,
forming a lumbar hernia.

Dissection. Reflection of the Trapezius. On the second day
the dissector must begin by reflecting the trapezius, working, it



58 THE SUPERIOR EXTREMITY

possible, in conjunction with the dissector of the head and neck.
Divide the muscle about two inches from the spines of the verte-
brae, and throw it laterally, towards its insertion. The trapezius
is very thin at its origin, and the greatest care must therefore be
taken not to injure the subjacent rhomboid muscles. The small
bursa between the tendon of insertion of the lower part of the
trapezius and the flattened apex of the spine of the scapula must
not be overlooked, and the nerves and vessels on the deep surface
of the muscle must be cleaned and preserved. They are the
accessory nerve and branches of the third and fourth cervical
nerves, the ascending branch of the transverse cervical artery,
and branches of the descending branch of the transverse cervical
artery^ The latter pass into the trapezius from between the
muscles of the second layer.

Nerves and Vessels of Supply to the Trapezius. A dis-
section of the deep surface of the reflected muscle will reveal
the following structures :

a. The accessory nerve.

b. Two or three nerves from the cervical plexus.

c. The ascending branch of the transverse cervical artery.

d. Twigs of the descending branch of the transverse cervical

artery.

These constitute the nervous and vascular supply of the
trapezius.

The nerves have already been displayed by the dissector of
the head and neck, as they cross the posterior triangle of the
neck. The branches from the cervical plexus come from the
third and fourth cervical nerves. On the deep surface of the
trapezius they join with branches of the accessory nerve to
form the subtrapezial plexus, from which twigs proceed into the
substance of the muscle. The terminal twig of the accessory
nerve can be traced nearly to the lower margin of the
trapezius.

The ascending branch of the transverse cervical artery, which
accompanies the accessory nerve, must be followed to the
anterior border of the trapezius, where it will be seen to
spring from the trunk of the artery at the point where it
divides into its ascending and descending branches.

The twigs from the descending branch of the transverse
cervical artery pierce the muscles of the second layer or pass
between them, close to the vertebral border of the scapula.

Dissection. The posterior belly of the omo-hyoid, the trans-
verse scapular artery, and suprascapular nerve" must now be
displayed, and the clavicular and scapular insertions of the
trapezius must be examined. Divide the trapezius into an upper



DISSECTION OF THE BACK 59

and a lower part by a transverse cut at the level of the angle
between the clavicle and the spine of the scapula, and verify the
attachment of the upper part to the posterior border of the lateral
third of the clavicle and the attachment of the lower part to the
medial border of the acromion and the upper margin of the
posterior border of the spine of the scapula. Next clean away the
fat in the area exposed and display the posterior belly of the
omo-hyoid muscle, the transverse scapular artery, the supra-
scapular nerve and the fascia over the supraspinatus. The supra-
spinatus covers the scapula between the spine and the upper
border of the bone. The posterior belly of the omo-hyoid is
attached to the lateral part of the upper border. The transverse
scapular artery crosses the upper border immediately lateral to
the omo-hyoid, resting on the superior transverse ligament,
which passes from the upper border to the coracoid process,
and separates the transverse scapular artery from the supra-
scapular nerve.

When the structures mentioned have been defined, draw the
scapula well over the edge of the block which supports the
thorax, and examine the muscles which attach the vertebral
border of the scapula to the vertebral column ; they are (i)
the levalor scapulae, (2) the rhomboideus minor, (3) the rhom-
boideus major. The levator scapulae is attached to the scapula
from the medial angle of the scapula to the flattened apex of the
spine of the scapula, the rhomboideus minor opposite the
flattened apex and the rhomboideus major from the flattened
apex to the inferior angle.

Cut through the fascia between the levator scapulas and the
rhomboideus minor about one inch medial to the scapula, and
find the dorsalis scapulas nerve which supplies the rhomboid
muscles and the descending branch of the transverse cervical
artery which accompanies it. (Fig. 26, p. 52.) These structures
will be traced to their terminations when the levator scapulas and
the rhomboids are reflected.

M. Omo-hyoideus, Arteria Transversa Scapulae (O.T.
Suprascapular Artery) et N. Suprascapularis. The slender
posterior belly of the omo-hyoid muscle will be seen to arise from
the upper margin of the scapula, immediately medial to the
scapular notch. It derives fibres also from the ligament
which bridges across this notch. It is supplied by a twig
from a nerve loop in the neck called the ansa hypoglossi.
The transverse scapular artery will be noticed to enter the
supraspinous fossa of the scapula by passing over the superior
transverse scapular ligament, whilst the suprascapular nerve
proceeds into the fossa under cover of that ligament (Fig. 38).

Mm. Bhomboidei. The two rhomboid muscles constitute
a thin quadrangular sheet of muscular fibres, .which extends
from the spinous processes of the vertebrae to the vertebral
margin of the scapula.

The rhomboideus minor is a narrow, ribbon -like fleshy



60 THE SUPERIOR EXTREMITY

band which runs parallel to the upper border of the major
rhomboid. It springs from the lower part of the ligamentum
nuchae, the spine of the seventh cervical vertebra, and frequently
also from the spine of the first thoracic vertebras. It is
inserted into the vertebral margin of the scapula opposite
the triangular surface at the flattened apex of its spine
(Fig. 38, p. 83). It is entirely covered by the trapezius.

The rhomboideus major arises from the upper four or five
thoracic spines, and the corresponding parts of the supraspinous
ligaments. Its fibres run obliquely downwards and laterally,
and end in a tendinous arch, which is attached to the
vertebral margin of the scapula, from the inferior angle to
the apex of the spine. The main attachment of the fibrous
arch is to the inferior angle, but it is bound to the vertebral
border from that point to the spine by fairly firm areolar
tissue (Fig. 38, p. 83). The greater part of the rhomboideus
major is covered by the trapezius ; only a small portion near
the inferior angle of the scapula lies immediately subjacent
to the deep fascia.

M. Levator Scapulas. The levator scapulae is an elon-
gated muscle which arises by four, more or less tendinous,
slips from the posterior tubercles of the transverse processes
of the upper four cervical vertebrae. It passes downwards
and backwards to be inserted into the vertebral margin of
the scapula, from the medial angle to the spine. It is supplied
by branches from the third and fourth cervical nerves.

Dissection. Clean the levator scapulae, taking care not to
injure the nerves which supply it. The muscle belongs partly to
the dissector of the head and neck and partly to the dissector of
the superior extremity. When both of them have studied its
attachment and nerve-supply, the muscle must be divided at
the middle of its length. The lower half is then to be turned
downwards and laterally to its insertion, and the dorsalis scapulas
nerve and the descending branch of the transverse cervical
artery, which lie deep to the muscle, are to be preserved and
followed to the upper margin of the rhomboideus minor.

Next cut through the rhomboids, from above downwards,
midway between the scapula and the spines of the vertebrae ;
remember that they are very thin, and take care not to injure the
serratus posterior superior, which is immediately subjacent to
them. Turn the medial part of each muscle towards the vertebral
spine and verify its attachment. Turn the lateral parts towards
the scapula and follow the dorsalis scapulae nerve and the
descending branch of the transverse cervical artery to their
terminations. The nerve gives branches to the levator scapulae
and to both the rhomboid muscles, and the artery not only supplies
the rhomboids but also the adjacent muscles on the scapula.



DISSECTION OF THE BACK 61



Online LibraryD. J. (Daniel John) CunninghamCunningham's manual of practical anatomy (Volume 1) → online text (page 7 of 44)