D. J. (Daniel John) Cunningham.

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cutaneous branches of the transverse scapular artery.

Nervi Cutanei Anteriores. The anterior cutaneous nerves
are the minute terminal twigs of the anterior rami of the
thoracic nerves. They become superficial by piercing the
pectoralis major muscle and the deep fascia, close to the
margin of the sternum. One will be found in each inter-
costal interval except the first ; and they are accompanied by
the cutaneous perforating branches of the internal mammary
artery, which serve as the best guides to the nerves. The
nerves and the arteries give slender twigs to the skin over
the sternum, and larger branches which run laterally and
may be traced as far as the anterior fold of the axilla. The
cutaneous perforating artery which appears through the third
intercostal space is usually the largest of the series, especially
in the female.

Nervi Cutanei Laterales. The lateral cutaneous nerves,
much larger than the anterior, arise from the anterior rami of
the thoracic nerves, and appear, on the side of the thorax,
along a line situated a little behind the anterior fold of the
axilla. They pierce the wall of the thorax in the interspaces
between the ribs, and divide into anterior and posterior
branches under cover of the serratus anterior muscle. At a
later stage the branches will be found appearing between the
digitations of the serratus anterior. The anterior branches
appear, as a rule, about an inch in front of the corresponding-
posterior branches, and then pass forwards over the lower
border of the pectoralis major muscle. From the lower
members of this series some minute twigs are given off, which
enter the superficial surfaces of the digitations of the external
oblique muscle of the abdomen which will be exposed by
the dissection of the abdomen. The posterior branches run
backwards, to the dorsal aspect of the trunk, over the anterior
border of the latissimus dorsi muscle (Fig. 16).

It is not advisable to attempt to secure the posterior branches of the
lateral cutaneous nerves in the meantime. They are best dissected along
with the other contents of the axilla.

The Mamma (Mammary Gland or Breast). In the female
the mamma forms a rounded prominence on the front and
also, to some extent, on the lateral aspect, of the thorax. It



PECTORAL REGION 15

lies in the superficial fascia, and its smooth contour is largely
due to the invasion of its substance by the fatty tissue of that
fascia.

A little below its mid-point, and at a level which usually
corresponds to the fourth intercostal space, the mamma is
surmounted by a conical elevation termed the papilla mamma.
or nipple. The nipple stands in the middle of a circular
patch of coloured skin which is called the areola mamma.




Teres major
Latissimus dorsi



Pectoralis maj
Lobules of the gland

Ampullae or sinuses of ducts

Serratus anterior

Fibrous trabeculae of the gland



FIG. 7. Dissection of the Mamma.

Within the nipple, and also subjacent to the areola, there is
no fat. A curious change of colour occurs in this region in
the female during the second month of pregnancy. At that
time the delicate pink colour of the skin of the nipple and
areola which was present in the virgin becomes converted to
brown, by the deposition of pigment, and it never again
resumes its original appearance.

The mamma extends, in a horizontal direction, from
the side of the sternum almost to the mid-axillary line on
the side of the thorax, and, in a vertical direction, from
the second costal arch above to the sixth costal cartilage



i6



THE SUPERIOR EXTREMITY



below. About two-thirds of the gland are placed upon the
pectoralis major muscle, whilst the remaining part, which
corresponds to its inferior and lateral third, extends beyond
the anterior fold of the axilla, and lies upon the serratus
anterior muscle. From the part which lies in relation to the
lower border of the pectoralis major a prolongation extends
upwards into the axilla, and reaches as high as the third rib.



Processes radiating out
from the corpus mammae



\



Sinus lactiferus
Ductus lactiferi




Pectoralis major



Fat lobule



FIG. 8. Section through a Mammary Gland prepared by the method
recommended by Sir Harold Stiles.

The mamma is not enclosed in a capsule, and in that
respect it differs from many other glands. Its lobules and
lobes are embedded between strands of fibrous tissue which
pass through the superficial fascia from the skin to the deep
fascia. The strands form the stroma or framework of the
gland. They support and bind together the various parts of



PECTORAL REGION 17

the true glandular tissue, which consists of cell-lined tubes,
and they attach the gland both to the skin and to the deep
fascia. The strands which pass to the skin have been called
the ligaments of Cooper.

The stroma and the gland tissue together form a conical
mass called the corpus mammce. From the surfaces and borders
of the general mass of the corpus mammae many processes
of stroma and gland substance project, and in the hollows
between the projections is deposited the fat upon which the
smooth and rounded contour of the organ depends.

The portions of the tubes of the gland which form the
secretion called milk are grouped together in smaller and
larger masses, called lobules and lobes, in the interstices of
the fibrous stroma of the gland. The portions of the tubes
which carry the secretion towards the nipple are called ducts.
The smaller ducts fuse with others to form larger ducts until
finally some fifteen or more terminal ducts, called lactiferous
ducts, converge towards the base of the nipple. Subjacent to
the areola each duct expands into a fusiform dilatation called
a lactiferous sinus, then it contracts, traverses the substance
of the nipple, and opens on its apex (Figs. 7 and 8).

In a well-injected subject twigs from the intercostal arteries,
and also from the perforating branches of the internal mammary
artery, may be traced into the mamma ; and other vessels,
called the external mammary branches of the lateral thoracic
artery, may be seen winding round the edge of the pectoralis
major, or piercing its lower fibres, to reach the gland.

By means of lymph vessels which issue from it in the
neighbourhood of the areola, and from its borders and its
deep surface, the mammae is connected with the axillary, the
sternal and the infraclavicular lymph glands, and with the
lymph vessels of the abdomen (Figs. 9, 14). The lymph vessels
are not, as a rule, visible in an ordinary dissecting-room
subject, for special methods of preparation are necessary for
their proper display, but they must be remembered, because
they are of the greatest importance in connection with the
spread of any malignant disease which has commenced in
the mamma.

In the male the mamma (mamma virilis) is quite rudi-
mentary. The nipple is small and pointed, and the areola
is surrounded by sparse hairs, which are never present in the
female.

VOL. i 2



1 8 THE SUPERIOR EXTREMITY

Dissection. If the subject is a female the dissector should
endeavour to make out some of the details described above.
The strands called the ligaments of Cooper were noted, as the
skin was removed from the surface of the gland (p. 17). Now
the skin of the areola must be detached from the surface of
the gland, and reflected towards the nipple. As that is done
try to make out the lactiferous sinuses (Fig. 7) and the terminal
ducts. If possible pass a bristle into one or other of the ducts
at the apex of the nipple and trace the duct to a lactiferous
sinus, and from the sinus trace the deeper part of the duct into
the substance of the gland. Next, with the aid of the scalpel,
gradually detach the gland from the deep fascia. Begin at
the upper border, and, as the gland is displaced, note the strands
of the stroma which connect its deep surface with the deep
fascia. It is along those strands that blood-vessels and lymph
vessels, which pierce the substance of the pectoralis major,
enter and leave the gland. Trace a process of the lateral
margin of the gland into the axilla behind the anterior axillary
fold. Finally, remove the gland by cutting the mammary
branches of the lateral thoracic artery at the lateral margin,
and the mammary branches of the anterior perforating arteries
at the medial margin, then examine the deep fascia of the
pectoral and axillary regions.

Deep Fascia. The deep fascia of the pectoral region is
a thin membrane which closely invests the pectoralis major.
It is attached above to the clavicle, and medially to the
front of the sternum. Below, it is continuous with the deep
fascia covering the abdominal muscles, and, at the lower
border of the pectoralis major muscle, it is continuous with
the axillary fascia. At the delto-pectoral triangle a process
from its deep surface dips in, between the deltoid and
pectoralis major muscles, to join the costo-coracoid membrane,
whilst, further laterally, it becomes continuous with the fascia
covering the deltoid muscle. The costo-coracoid membrane
will be described later (p. 24).

Fascia Axillaris. The axillary fascia is a dense felted
membrane which extends across the base of the axilla. It
is continuous anteriorly with the deep fascia over the
pectoralis major, posteriorly with the fascial sheaths of the
latissimus dorsi and the teres major muscles, medially with
the deep fascia on the surface of the serratus anterior,
whilst laterally it is continuous with the deep fascia on
the medial surface of the proximal part of the arm. It is
drawn up towards the hollow of the axilla, and the
elevation is due chiefly to the connection of its deep surface
with the fascial sheath of the pectoralis minor, and partly
to its attachment to the areolar tissue which fills the axillary



PECTORAL REGION 19

space. In a well- injected subject a small artery, from the
distal part of the axillary trunk, may be seen ramifying on
the surface of the fascia.

Dissection. Cut through the deep fascia along the sulcus
between the pectoralis major and the deltoid, and display the
cephalic vein (Figs. 31, 33) and the deltoid branch of the thoraco-
acromial artery which accompanies it. " Clean " them by
removing the loose fascia in which they are embedded. Follow
both vessels upwards to the delto-pectoral triangle where they
disappear under cover of the upper border of the pectoralis
major.

In the delto-pectoral triangle look for the delto-pectoral
lymph glands which are sometimes present. Lymph glands
are rounded or ovoid masses of fairly dense tissue, which vary
in colour; they may be yellowish-pink, rose-pink, reddish-
brown, purple-brown, or in some regions quite black. Their
surfaces are usually glistening, and attached to the borders
and surfaces are many fine white vessels, the lymph vessels,
which convey a fluid called lymph to and from the glands.
Lymph glands vary very much in size, and the delto-pectoral
glands may be as small as a pin-head or as large as a good-sized
pea. After the contents of the delto-pectoral triangle have been
studied, clean the anterior part of the deltoid and the whole of
the pectoralis major muscle, and note the natural separation of
the latter muscle into sternal and clavicular parts.

The " cleaning " of a muscle means the removal of the
whole of the deep fascia from its surface. To do this success-
fully the dissector must follow three rules, (i) He must cut
boldly down through the deep fascia till he exposes the red
fibres of the muscle. (2) As he removes the fascia he must
keep the knife edge playing against the fibres of the muscle.
(3) As he makes his cuts he must carry the knife blade in the
direction of the fibres of the muscle. If he follows rules i and
2 he will not leave a thin film of fascia on the muscle, and as
he follows rule 3 he will find that the direction of his incisions
changes as the course of the fibres of the muscle changes. If
the work is well done the deep fascia should be removed from
the muscle as a continuous unperforated layer of fibrous tissue,
and the surface of the muscle will be clean.

To clean the anterior part of the deltoid, cut through the
deep fascia along the anterior border of the muscle, and reflect
the fascia until the base of the skin flap is reached. As the
fascia is reflected some cutaneous twigs of the axillary nerve
may be noted piercing the surface of the muscle, and filaments
of the lateral cutaneous nerve of the arm will also be found
(see Figs. 31, 32, 33).

To clean the pectoralis major commence at the upper border
of the muscle on the right side, and at the lower border on the
left side, reflecting the fascia in the first case downwards, and
in the second upwards. Before the removal of the fascia is
begun make the muscle tense by abducting the arm.

The delto-pectoral glands, sometimes represented by a
single gland, receive lymph from the lateral side of the arm



20



THE SUPERIOR EXTREMITY



and from the shoulder by lymph vessels which accompany
the cephalic vein, and they transmit it to lymph vessels which
connect the delto- pectoral glands with the infraclavicular
glands (see Figs. 9, 30).

M. Pectoralis Major. The powerful pectoralis major
muscle extends from the anterior aspect of the thorax to the
humerus. It is divided by a deep fissure into a clavicular and

Cephalic vein
I Central axillary glands
! / Delto-pectoral gland
; ; ,! Infraclavicular glands

Gland superficial to costo-coracoid membran
Interpectoral glands
/ Lymph vessels passing to
i / ; sternal glands




Lymph vessels from arm /
Lateral axillary glands
Posterior or subscapular axillary glands
Anterior or pectoral axillary glands



Lymph vessels from deep parts of mamma

passing to interpectoral, infraclavicular

and also to supraclavicular glands



Lymph vessels passing to join other lymph
vessels in extraperitoneal tissue



FIG. 9. The Lymph Glands and Vessels of the Axilla and Mamma.

a sternocostal portion. The fissure penetrates through the
entire thickness of the muscle, the clavicular and sternocostal
portions being distinct, except close to their insertions. The
clavicular portion arises by short tendinous and muscular fibres
from an impression on the medial half of the anterior surface
of the clavicle. The superficial part of the sternocostal portion
takes origin, by fleshy fibres, (i) from the anterior surface of
the sternum, (2) from the aponeurosis of the external oblique
muscle, and (3) occasionally from the sixth rib near its



AXILLARY SPACE



21



cartilage. The deeper part arises by a variable number of
muscular slips from the cartilages of the upper six ribs.

The muscle is inserted, by a flattened bilaminar tendon,
into the lateral lip of the intertubercular sulcus of the
humerus, and the fibres of the muscle undergo a rearrange-
ment as they converge upon the tendon. The greater
part of the clavicular portion joins the anterior lamina of the
common tendon ; some of the most medial clavicular fibres,
however, are inserted directly into -the humerus, distal to
the tendon, whilst a few gain attachment to the deep fascia
of the arm, and others become adherent to the adjacent
part of the deltoid.

The fibres of the sternocostal portion of the muscle do
not all pass in the same direction but they all join the laminae

Trapezoid
ligament




Costo-clavicular ligament



Conoid ligament



FIG. 10. Inferior Surface of the Clavicle with the Attachments of the
Muscles mapped out.

of the tendon of insertion. The superior fibres descend
slightly, the intermediate fibres pass horizontally, whilst the
inferior fibres ascend, and, at the same time, gain the deep
surface of the rest of the muscle. A smooth, full, and rounded
lower border of the muscle is thus formed \ it constitutes the
anterior fold of the axilla. The attachments of the muscle
to the humerus will be studied in detail at a later stage
of the dissection (p. 87).

The pectoralis major is supplied by the medial and lateral
anterior thoracic nerves. It is an adductor of the superior
extremity and a medial rotator of the humerus.

Axilla. The axilla is the hollow or recess between the
upper part of the side of the thorax and the proximal part
of the arm. When the arm is abducted from the trunk,
and the areolo-fatty tissue which occupies the axilla is
removed, the space disclosed has the form of a four-sided
pyramid. The apex, or narrow part of the space, lies



22 THE SUPERIOR EXTREMITY

immediately to the medial side of the coracoid process, and
is directed upwards towards the root of the neck, whilst the
wider part or base of the space looks downwards. The
medial wall, formed by the thorax, is of greater extent than
the lateral wall which is formed by the arm. It follows,
therefore, that the anterior and posterior walls converge as
they proceed laterally, and, because the posterior wall is
longer, from above downwards, than the anterior, the posterior
border of the base is lower than the anterior.

Before beginning the dissection of the space, the dissector should have
a general knowledge of its boundaries and of the manner in which the
contents are disposed in relation to the boundaries.

Boundaries of the Axilla. The four walls of the axilla are
(i) anterior, (2) posterior, (3) medial, and (4) lateral. The
anterior wall is formed by the two pectoral muscles, the
subclavius and the fascia which surrounds the pectoralis
minor and attaches its upper border to the clavicle and its
lower border to the floor of the axilla, and to the deep fascia
on the medial side of the arm. The pectoralis major forms
the superficial stratum, and is spread out over the entire
extent of the anterior wall. The pectoralis minor lies
posterior to the pectoralis major, and takes part in the
formation of the middle third of the anterior boundary. The
fascia which fills the gap between the pectoralis minor and
the clavicle is called the costo-coracoid membrane ; it splits
above to enclose the subclavius muscle, and along the lower
border of that muscle it is stronger than elsewhere. The
lower border of the anterior wall is the anterior fold of the
axilla. It is formed by the lower border of the pectoralis
major, strengthened, medially, by the lower border of the
pectoralis minor, which projects beyond the major near the
side of the thorax.

The posterior wall of the axilla is formed by the lateral
part of the subscapularis muscle, by a portion of the latissimus
dorsi and its tendon, and by the teres major muscle. The
subscapularis covers the costal surface of the scapula. The
latissimus dorsi winds from the back, round the medial part
of the lower border of the teres major to gain its anterior
surface; thus the lower border of the posterior wall, which
constitutes the posterior fold of the axilla, is formed in its
medial part by the latissimus dorsi, and laterally by the
inferior margin of the teres major.



AXILLARY SPACE



In the medial wall are parts of the upper five ribs with
the intervening intercostal muscles ; they are covered by the
corresponding digitations of the serratus anterior muscle.

The lateral wall is formed by the humerus and the conjoined
proximal parts of the coraco-brachialis and the short head of
the biceps brachii muscles.

At the apex of the space is the narrow triangular interval
through which the axilla communicates with the neck ; it is
frequently called the cervico- axillary canal. It is bounded
anteriorly by the clavicle, medially by the outer border of
the first rib, and posteriorly by the superior margin of the
scapula ; through it pass the axillary vessels and the big
nerve cords of the brachial plexus on their way from the



1. Proximal end

humerus.

2. Scapula.

3. Rib.

4. Pectoralis major.

5. Serratus anterior.

6. Subscapularis.

7. Axillary vein.



of




8. Axillary artery.

9. Long heafl of biceps.
10. Conjoined origin of

short head of biceps
and coraco - brachi-
alis.
n, 12, 13. Brachial nerves.



FIG. ii. Diagram of section through the Axilla of the Left Side.

neck to the arm. The wide base or floor of the space is
closed by the vaulted axillary fascia.

Contents of the Axilla. The axillary artery and vein,
with the large brachial nerves, which supply the superior
extremity, and the axillary lymph vessels and lymph glands,
are the most important contents of the axilla. They are
all embedded in the soft axillary fat. Except at the apex
of the space, the great vessels and nerves lie close to the
lateral wall, and follow it in all the movements of the arm.

Dissection. Cut through the clavicular fibres of the pectoralis
major, immediately below their attachment to the clavicle, and
turn them towards their insertion. At the same time, secure the
branches of the lateral anterior thoracic nerve which pass into
the deep surface of the muscle. Follow the cephalic vein and
the deltoid branch of the thoraco-acromial artery medially, under
cover of the clavicular part of the pectoralis major, and secure the
acromial and pectoral branches of the latter artery. Clean those
vessels and, directly below the clavicle, display the costo-
coracoid membrane, and, more inferiorly and laterally, the fascia



24 THE SUPERIOR EXTREMITY

on the lateral part of the pectoralis minor. Cut through the
sternocostal part of the pectoralis major about two inches from
the lateral border of the sternum. Turn the medial part towards
the median plane ; verify its attachment to the costal cartilages
and to the sternum and to the aponeurosis of the external oblique
muscle of the abdomen. Turn the lateral part of the muscle
towards the arm ; whilst doing that, secure the medial anterior
thoracic nerve, which perforates the pectoralis minor and ends
in the pectoralis major. Examine the insertion of the pectoralis
major. Note that the tendon of insertion consists of two laminae
which are united together below ; in other words, the tendon is
folded on itself ; and between the two laminae a mucous bursa
is frequently interposed. The clavicular fibres and the upper
sternocostal fibres are attached to the anterior lamina, the lower
sternocostal fibres to the posterior lamina. Both laminae are
attached to the lateral lip of the intertubercular sulcus of the
humerus, but the deep lamina ascends to a more proximal level,
and becomes continuous with a layer of fascia which is attached
to the lesser tubercle of the humerus. The inferior border of the
tendon of insertion is continuous with the deep fascia of the arm.
When the pectoralis major is completely reflected a continuous
sheet of fascia is exposed, which extends from the clavicle
superiorly to the axillary fascia inferiorly, and from the wall of
the thorax medially to the arm laterally ; the sheet of fascia is
the so-called clavipectoral fascia or suspensory ligament of the
axilla. It is because of the attachment of that fascial sheet to
the clavicle superiorly and to the axillary fascia inferiorly that
the floor of the axilla is raised as the arm is abducted from the
side and the clavicle is elevated. The pectoralis minor muscle,
passing obliquely from its origin on the thoracic wall to its
insertion into the coracoid process of the scapula, runs through
the substance of the clavipectoral fascia and divides it into three
parts : (i) the part above the muscle, (2) the part which encloses
the muscle, and (3) the part below the muscle. The uppermost
part is the costo-coracoid membrane, the intermediate part is the
sheath of the pectoralis minor. No special term is applied to
the lowest part, but it should be noted that it lies posterior to the
lower part of the pectoralis major, and that it covers the distal
portions of the axillary vessels and nerves.

Membrana Costocoracoidea. The costo-coracoid mem-
brane occupies the gap between the clavicle and the pectoralis
minor. It extends from the first rib medially to the coracoid
process laterally, and from the clavicle above to the pectoralis
minor below. Its upper part is split into two layers, an
anterior and a posterior, which are attached to the corre-
sponding borders of the clavicle. Enclosed between them is
the subclavius muscle. The strongest part of the membrane
is that which extends along the lower border of the sub-
clavius, from the first rib to the coracoid process ; that portion
is frequently called the costo-coracoid ligament. The membrane
is continuous below with the fascial sheath of the pectoralis



AXILLARY SPACE 25

minor and posteriorly with the fascial sheath of the axillary
vessels (Fig. 12). It is perforated, above the upper border
of the pectoralis minor, by the cephalic vein, the thoraco-



Online LibraryD. J. (Daniel John) CunninghamCunningham's manual of practical anatomy (Volume 1) → online text (page 4 of 44)