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John J. (John Joseph) McGrath.

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168 THORAX.

surfaces look almost directly upward and downward. It is set so
obliquely that its posterior end, head, articulates with the upper
part of the body of the first dorsal vertebra, whereas its anterior
end, at its attachment to the sternum, is upon a level with the inter-
vertebral pad between the second and third dorsal vertebras. The
inner border of this rib presents a tubercle for the attachment of
the scalenus anticus muscle; external to this tubercle, upon the
upper surface of the rib, there is a groove for the subclavian artery.
The subclavian vein also passes across the upper surface of the first
rib, but internally to the artery, the tendon of the scalenus anticus
being interposed between the two vessels.

The inner border of the first rib is in direct relation with the
dome of the pleura and the apex of the lung.

The Costal Caetilages. — These are the elastic bands which
join the ribs to the sternum (except the eleventh and twelfth). The
cartilage of the first rib is very short. The first and second costal
cartilages, as they pass to the sternum, are directed somewhat down-
ward like their ribs. The cartilage of the second rib articulates
with the sternum at the junction of the manubrium with the glad-
iolus. The cartilage of the third rib is directed horizontally; the
cartilages of the fourth, fifth, sixth, and seventh ribs are directed
upward with increasing obliquity as they pass to the sternum. The
cartilages of the eighth, ninth, and tenth make quite a sharp turn
upward toward the sternum at the angle of junction with their ribs,
and do not reach the sternum directly, but are fixed each to the
cartilage immediately above, and finally, through the junction of the
cartilage of the eighth rib with that of the seventh, to the sternum.
The cartilages of the eleventh and twelfth ribs are short and free.

The Steknttm. — This bone is rarely fractured, owing to the
elasticity of the parts with which it articulates. It consists of a
manubrium, or handle; a gladiolus, or body; and a cartilaginous tip,
the ensiform or xiphoid cartilage. The junction between the manu-
brium and the body is marked by a prominent transverse line, and
presents an angle directed forward: angulus Ludovici. This trans-
verse ridge, which is readily felt under the skin, is an important
landmark in counting the ribs: it corresponds to the articulation of
the costal cartilage of the second rib with the sternum.

The ensiform cartilage varies in length and shape; its lower
extremity is usually on a level with the tenth dorsal vertebra; it
may be bifurcated or deflected to one side. The junction of the



SURGICAL ANATOMY OF THE THORACIC WALL. 169

ensiform cartilage with the body of the sternum corresponds with
the line that marks the lower border of the heart as it lies within
the chest behind the sternum.

The Muscles of the Chest Wall. The Inteecostal Muscles
are placed between the ribs and costal cartilages, and consist of two
sets: external and internal.

The External Intercostals. — The fibers of the external inter-
costals have a direction similar to those of the external oblique
muscle of the abdomen: that is, from above downward and forward.
In front, between the costal cartilages, the muscular fibers are ab-
sent, their place being taken by aponeurotic bands, the ligamenta
intercostalia anterior, which represent the muscles.

The Internal Intercostals. — The direction of the fibers of the
internal intercostal muscles is the reverse of those of the external.
They correspond to the internal oblique muscle of the abdomen,
and their fibers have a similar direction: upward and forward. Be-
hind, the internal intercostals are deficient, their place being occu-
pied by aponeurotic sheaths: the ligamenta intercostalia posterior.

The Teiangttlaeis Steeni is situated anteriorly within the
chest. It is a thin sheet of muscle which is attached along the
lateral border of the posterior aspect of the sternum. It spreads
upward and outward in four or five processes, which are attached
separately to the inner surfaces of the cartilages of the second to
the sixth ribs. The internal mammary artery is located between
this muscle and the costal cartilages. The triangularis sterni is the
transversus thoracis anterior of Henle.

The Musculi Stjbcostales are a few sets of muscular fibers
that are found upon the internal surfaces of the posterior ends of
the ribs near the vertebral column; the direction of the fibers of
these muscles is similar to that of the internal intercostals: they
reach from the inner surface of one rib to the first or second rib
above. These muscles correspond to the musculus transversus
thoracis posterior of Henle, and together with the triangularis sterni
are the analogues of the transversus abdominis, the most internal,
deepest, of the flat muscles of the abdomen.

The Fasciae of the Chest. — A thin fascia covers the outer surface
of the ribs and the external intercostals. A similar fascia is spread
over the inner surface of the ribs and the internal intercostals, tri-
angularis sterni, and subcostales. This fascia corresponds to the
fascia transversalis of the abdomen, and is known as the fascia endo-



170 THORAX.

thoracica. The fascia endothoracica is also spread over the thoracic
surface of the diaphragm. It lines the whole inner surface of the
thoracic cavity, and is everywhere interposed between the parietal
layer of the pleura and the inner surface of the chest, serving thus
to bind the pleura to the chest wall and at the same time to
strengthen it. Upon the posterior surface of the sternum this fascia
iorms a strong fibrous layer. Above it projects into the root of
the neck together with the dome of the pleura, which it strengthens
and fixes to the vertebrae and to the deep surface of scaleni muscles,
etc.

The Internal Mammary Artery supplies the front part of the
intercostal spaces and the diaphragm and gives perforating branches
to the muscles of the chest and to the mammary gland. At its origin
from the first part of the subclavian artery it lies behind the sub-
clavian vein, resting upon the pleura, and is crossed by the phrenic
nerve. It passes down into the thoracic cavity and descends along-
side of the sternum, a distance of from 5 to 10 mm. intervening
between it and the lateral border of this bone. Behind the seventh
costal cartilage the internal mammary artery divides into the
musculo-phrenic and the superior epigastric. The musculo-phrenic
continues downward parallel with the free border of the ribs, sup-
plying branches to the intercostal spaces. The superior epigastric
enters the posterior sheath of the rectus, anastomosing with the deep
epigastric, which is derived from the external iliac, and in this way
forms an important communication between this trunk and the sub-
clavian. The internal mammary artery is accompanied by two veins,
one upon either side, but above these two unite to form a single
vein, which lies to the inner side of the artery. The artery is also
accompanied by a chain of lymphatic glands.

Within the chest the artery rests upon the costal cartilages and
the internal intercostal muscles, alongside the sternum, and is sepa-
rated from the parietal pleura by the fascia endothoracica and the tri-
angularis sterni muscle. Opposite each intercostal space the internal
mammary gives off an intercostal branch, which, passing outward,
divides into two, and these, anastomosing with the intercostal
branches from the aorta, serve to establish a communication between
the subclavian and the aorta. These intercostal branches are located
between the internal and the external intercostal muscles close to
the upper and lower borders of the contiguous ribs. The internal
mammary gives off perforating branches, which pass forward through



REGIONS OF THE CHEST. 171

the intercostal spaces to supply the muscles of the hreast and the
mammary glands. Those which pass through the second, third, and
fourth intercostal spaces are large, and are distributed to the mam-
mary gland.

The Diaphragm. — The lower orifice of the thorax is closed in
by the diaphragm. This is a musculo-tendinous partition which
separates the thorax from the abdominal cavity. It forms the floor
of the thoracic cavity and the roof of the abdomen. The thoracic
surface of the diaphragm is covered by the fascia endothoracica and
the diaphragmatic portion of the parietal pleura. Its middle part
from before backward forms the floor of the mediastinum, and upon
either side of this it forms the bottom of each pleural cavity.

The position of the diaphragm, immediately after death, corre-
sponds with that found at the end of quiet expiration during life,
but after a short time, owing to the further collapse of the lungs,
it reaches to a still higher level.

Luschka places the highest point reached by the diaphragm
at the end of forced expiration upon the right side at the level of
the fourth rib. Most authors say that this is too high and give, in-
stead, the fourth intercostal space. Upon the left side the dia-
phragm does not reach as high as upon the right by the breadth
of one rib.

The upper orifice of the thoracic cavity is shut in on either side
by the arching subclavian artery, scalenus anticus and medius mus-
cles, and the fascia endothoracica. This fascia is intimately blended
with the dome of the pleura, and attaches the same to the adjacent
fixed points.

THE REGIONS OF THE CHEST.

The following imaginary lines serve to facilitate the location of
points upon the chest: —

1. The midsternal, which passes through the middle of the
sternum.

2. The lateral sternal, which corresponds to the lateral border
of the sternum.

3. The mammary, which is drawn through the nipple.

4. The parasternal, which is drawn midway between the lateral
horder of the sternum and the mammary line.

5. The axillary, which is located midway between the anterior
and the posterior borders of the axilla.



172 THORAX.

6. The scapular passes through the lower angle of the scapula.
The chest is divided into a number of regions as follows: — -

1. The sternal.

2. The upper anterior pectoral, which is subdivided into a
clavicular, an infraclavicular, and a mammary.

3. The lower anterior pectoral.

4. The lateral pectoral.

The Sternal Region.- — This region corresponds to the sternum-
It is depressed below the level of the rest of the chest, especially
in muscular subjects and in females.

The skin of this region, in the male, is usually covered with hair
and is rich in sweat-glands. The subcutaneous tissue is poor in fat
and allows ready palpation of the sternum beneath. The skin and
periosteum covering the sternum are so intimately blended with each
other that separation between these two layers is somewhat difficult,,
and, therefore, collections of blood or pus beneath the skin in this
region remain circumscribed, as is the case in the subcutaneous tissue
of the scalp. Above, we observe the upper notched border of the-
sternum with the sterno-clavicular articulation upon either side and
the attachment of the tendon of the sterno-mastoid. Below is the
ensiform cartilage, to which is attached the linea alba. The junction
of the manubrium with the body of the sternum is marked by a
prominent transverse ridge and presents an angle directed forward:
the angle of Ludovici. The sternum forms the anterior wall of the-
mediastinal space, and its posterior surface is in close relation with
the pleura and the edges of the lungs. Below, the heart, inclosed
in the pericardial sac, lies close behind the sternum.

The Upper Anterior Pectoral Region. — This area corresponds to
the region of the pectoralis major muscle, and shows the prominence
of the breast surmounted by the nipple and the areola. The skin is
soft, especially in women, and during lactation is marked by blue
lines, which correspond to large superficial veins. The skin is freely
movable, owing to the looseness of the subcutaneous tissue, which
is rich in fat and within which the mammary gland is contained.
The mammary gland is freely movable upon the underlying pec-
toralis major muscle. The anterior surface of the pectoralis major
is covered by a thin, cellular fascia, which also lines the posterior
aspect of this muscle. Beneath the pectoralis major are the pec-
toralis minor and the subclavius muscle. The pectoralis major and.
minor form the front wall of the axilla.



REGIONS OF THE CHEST. 173

The Pectoealis Majoe is a broad, flat muscle which occupies
all of this region. It takes its origin from the cartilages of the six
or seven upper ribs and from the edge of the sternum: the sternal
portion of the muscle. It also arises from the inner half of the
anterior surface of the clavicle: the clavicular portion of the mus-
cle. From these points of origin the fibers converge to form a flat
tendon, about two inches broad, which is attached to the outer edge
or lip of the bicipital groove: a depression which marks the upper
part of the front of the humerus. The pectoralis major muscle is
covered by a thin fascia, which dips down between its fasciculi and
from which the overlying fat and mammary gland are readily sepa-
rated. This fascia is rich in lymphatics, which may become involved
in disease of the mammary gland. Below, this fascia is continuous
with the superficial fascia which covers the abdominal muscles and
laterally with that which covers the serratus magnus. It dips down
into the space between the deltoid and the pectoralis major, and is
there continuous with the loose fascia that invests the pectoralis
minor and the posterior surface of the pectoralis major.

The Pectoealis Minor. — This muscle is exposed by dividing
the tendon of the pectoralis major close to its insertion and reflect-
ing the muscle downward. The pectoralis minor arises from the tip
of the coracoid process; passing downward and inward and becoming
broader, it is attached to the third, fourth, and fifth ribs. The
pectoralis minor is invested by a fascia which is continued upward
and inward beyond the upper border of the muscle, covering in the
first part of the axillary artery and adjoining structures and the sub-
clavius muscle. This layer of fascia is called the costo-coracoid
membrane and is attached to the under surface of the clavicle and
to the first rib. It is somewhat thickened, and perforated by various
vascular and nervous branches, which pass to and from the axillary
vessels and adjacent nerves.

The Subclavius Muscle. — This muscle is exposed after the
costo-coracoid membrane has been removed. It arises from the
under surface of the clavicle and passing downward and inward is
attached to the cartilage of the first rib.

This upper anterior pectoral region may be considered as the
clavicular, the infraclavicular, and the mammary regions.

The Clavicular Kegion. — The clavicle can be readily pal-
pated beneath the freely movable integument which covers it from
its inner end, where it articulates with the sternum, to its outer end,



174 THORAX.

where it articulates with the acromion process of the scapula. The
acromion process of the scapula forms the most external and promi-
nent point of the shoulder.

Beneath the skin in the clavicular region are found the platysma
and the deep fascia.

To the upper surface and posterior border of the clavicle are
attached, internally, the sterno-mastoid muscle, and externally the
trapezius. To the inner half of the front surface of the clavicle is
attached the pectoralis major muscle (clavicular portion), and, to
its outer half, the deltoid muscle.

The under surface of the clavicle shows, at its inner end, the
attachment of the rhomboid ligament. This ligament extends be-
tween the under surface of the clavicle and the cartilage of the first
rib. External to this the subclavius muscle arises from the under
surface of the clavicle.

The inferior surface of the outer end of the clavicle is con-
nected with the coracoid process of the scapula by strong ligamentous
bands.

Beneath the clavicle, between it and the first rib, the blood-
vessels and nerves pass from the root of the neck into the axilla.

The Infeaclaviculak Eegion. — This is the region below the
clavicle. Between the pectoralis major and the deltoid muscle, close
to the clavicle, there is a triangular depression, the fossa of Mohren-
heim: the infraclavicular fossa.

In the space, or groove, between the pectoralis major and the
deltoid are lodged the cephalic vein and the descending branch of
the acromio-thoracic artery, which is given off from the axillary.
If the two muscles are widely separated, we expose the upper part
of the pectoralis minor, covered by its fascia, some loose connective
tissue and fat, and the coracoid process. This process is readily felt
underneath the skin, and in thin persons can be seen.

If the pectoralis major is cut away from its attachment to the
clavicle and from the upper part of the sternum and reflected down-
ward, the infraclavicular region proper is uncovered. The pectoralis
minor muscle is now more freely exposed. The cephalic vein may
be seen passing from without inward across the pectoralis minor
into a mass of fat and connective tissue on the inner side of the
muscle, where it disappears through an opening in the costo-coracoid
membrane to reach the first part of the axillary vein, which lies
underneath this membrane.



REGIONS OF THE CHEST. 175

The acromio-thoracic and branches of the superior thoracic
which are derived from the axillary artery are seen to emerge through
openings in the costo-coracoid membrane, as is also the external
anterior thoracic nerve, which supplies the pectoralis major.

The costo-coracoid membrane is a sheet of fascia which is con-
tinued from the inner or upper border of the pectoralis minor mus-
cle upward and inward, and is attached to the under surface of the
clavicle and to the first rib; it covers in the first part of the axillary
artery and the structures that accompany it and the subclavius mus-
cle. When the costo-coracoid membrane is removed, we expose the
first part of the axillary artery and its acromio-thoracic and superior
thoracic branches, the cords of the brachial plexus, which lie above
the artery, and the axillary vein, which lies below and internal to the
artery. The cephalic vein may be seen passing across the axillary
artery to enter the axillary vein. All these structures are gathered
together into a single bundle, and are accompanied by a mass of
fat, connective tissue, and lymphatics (see Fig. 183).

The Mammaey Eegion (Beeast). — The mammary gland is
rudimentary in the male and naturally well developed in the female.
It rests upon the pectoralis major muscle from the third to the sixth
rib. In unmarried and in young females it is hemispheroidal, firm,
and projects forward; but after child-bearing, and especially in some
races more than others, it is pendulous, and hangs down over the
lower part of the thorax.

The skin of this region is thin and fine and is freely movable
upon the underlying tissue. The superficial veins may show through
the skin as irregular blue streaks. The skin of the nipple is espe-
cially thin and pigmented, and may be fissured and split, and shows
the orifices of the milk-ducts, fifteen to twenty in number, as very
fine, needle-point openings; through these infection may reach the
mammary gland tissue proper.

In the unpregnant the nipple is depressed and pinkish, but is
prominent and dark colored during pregnancy. The nipple is sur-
rounded by a pigmented area, areola, which is fixed to the under-
lying tissue and marked by little nodules which correspond to se-
baceous and sweat-glands.

In the unmarried the mammary gland proper is small, the promi-
nence of the breast being due chiefly to the abundance of the fatty
tissue in which the gland is imbedded. It does not reach its full
development until after pregnancy. The mammary gland is a teg-



176 THORAX.

mentary organ inclosed within its own proper fibrous capsule and
lodged in the subcutaneous fat. It consists of a number of lobules,
which are separate and distinct from each other; so that the secre-
tion of milk and nursing may be continued even after one or more
lobules have become the seat of a suppurative process. Between
the mammary gland and the anterior surface of the pectoralis major
muscle there is a layer of loose fatty tissue, which permits the gland
to be freely moved about upon the surface of the muscle.

Occasionally a process of gland tissue almost entirely discon-
nected from the main gland may be found lying under the border
of the pectoralis major, dipping beneath the muscle into the axilla.
This process of gland tissue is often difficult to recognize. All the
ducts of the gland converge from the periphery toward the nipple;
they may become occluded and distended, giving rise to cystic tumors
whose contents consist of milk or of a buttery material: galactocele.

The arteries of the breast consist of perforating branches from
the internal mammary, especially the second and third and branches
of the long thoracic from the axillary. Of the veins, the superficial
ramify beneath the skin and the deep ones accompany the arteries.

The lymphatics are important and of these there are two sets:
those of the integument and those which drain the gland proper.
The lymphatics of the integument are very superficial and numerous,
especially upon the nipple and in the areola; corresponding to the
region of the areola, they form a fine capillary net-work which
spreads outward toward the periphery, some branches dipping in-
ward to enter a plexus which surrounds the milk-ducts beneath the
skin of the areolar region. The lymphatics from the gland proper,
from the acini and substance of the gland, are abundant. Accord-
ing to Sappay, they all tend toward the surface and end as good-
sized vessels in the plexus already mentioned which surrounds the
milk-ducts beneath the skin of the areola. The lymph from this
subareolar plexus is collected into two main channels: one above
and one below the nipple. These lymphatic vessels pass outward
toward the outer border of the gland, and, after being joined by one
or two vessels from the periphery of the gland, terminate in the
nearest lymphatic nodes, which are found near the anterior wall of
the axilla in the neighborhood of the third and fourth ribs, being
covered usually by the edge of the pectoralis major. These are, as
a rule, the first lymphatic nodes to become involved in disease of
the mammary gland. The lymphatic nodes in the root of the neck



MEDIASTINUM AND CONTENTS. 177

also receive tributaries from the breast, and may be found involved
when the mammary gland is diseased.

The Lower Anterior Pectoral Region. — This is the area which
lies between the lower limits of the pectoralis major muscle and
the free border of the ribs. This region is important surgically only
on account of the structures which lie beneath it, within the chest
and abdomen.

The Lateral Pectoral Region. — This space is included between
the border of the pectoralis major in front and that of the latissimus
dorsi behind. It presents the ribs covered by serrations of the ser-
ratus magnus and by the latissimus dorsi and obliquus abdominis
externus.

The arteries of this region are derived from the axillary (long
thoracic) and intercostals. The posterior thoracic nerve is found in
this region descending upon the serratus magnus, which it supplies.

THE MEDIASTINUM AND CONTENTS.

The mediastinum is a space within the chest, between the two
pleural cavities, which is occupied by the heart and pericardium, the
thymus or its remains, the trachea, oesophagus, aorta, and several
nerves, and a mass of loose connective tissue and lymphatics.

Eather more of the space lies to the left of the middle line
than to the right. It is limited in front by the sternum, behind by
the vertebral column, and its floor is formed by the diaphragm.
Above, the loose connective tissue of this space is continuous into
the root of the neck with that which surrounds the oesophagus and
trachea and the great vessels in the neck. Laterally the mediastinum
is walled off on either side from the pleural cavity by the parietal
pleura (mediastinal portion of the parietal pleura).

The mediastinum, as mentioned above, is not an empty space,
but is fairly closely occupied by various organs. In the lower part
of this space, in front, is the heart, inclosed within its pericardial
sac; behind the heart, between it and the vertebral column, the



Online LibraryJohn J. (John Joseph) McGrathSurgical anatomy and operative surgery, for students and practitioners → online text (page 17 of 52)