Chest wall and breast
936
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A Fig. 53.9 Superior surfaces of
Groove for subclavian vein
selected ribs, left side. A, First
Scalene tubercle rib. B, Second rib. C, Third rib.
D, Inferior surface of eighth rib,
Head left side. (With permission from
Waschke J, Paulsen F (eds),
Sobotta Atlas of Human Anatomy,
B Neck
15th ed, Elsevier, Urban &
Groove for subclavian artery Fischer, 2013.)
Tubercle
Body of rib (shaft of rib)
Neck; crest
C
Tubercle
Head
Neck
Articular facet of tubercle
Tubercle
D Shaft
Head; crest
Articular facet of head
Neck
Neck; crest
Articular facet of tubercle
Tubercle
Costal groove
and subclavian vessels are superior and apt to suffer compression in a The groove anterior to the scalene tubercle forms a bed for the subcla-
narrow angle between the rib and scalenus anterior. Hence, cervical ribs vian vein, and the rough area between this and the first costal cartilage
may first be revealed by neurovascular symptoms, particularly those gives attachment to the costoclavicular ligament and, more anteriorly,
caused by pressure on the eighth cervical and first thoracic spinal nerves. to subclavius. The subclavian artery and (usually) the lower trunk of
A cervical rib (pleurapophysis) may show synostosis or diarthrosis the brachial plexus pass in the groove behind the tubercle. Behind this,
with either the anterior (parapophysial) or posterior (diapophysial) scalenus medius is attached as far as the costal tubercle.
‘roots’ of the so-called seventh cervical transverse process or, more The external border is convex, thick posteriorly and thin anteriorly.
usually, with both. It is covered behind by scalenus posterior descending to the second rib.
The first digitation of serratus anterior is, in part, attached to it, behind
First rib the subclavian (arterial) groove. The internal border is concave and thin,
and the scalene tubercle is near its midpoint. The suprapleural mem-


brane, which covers the cervical dome of the pleura, is attached to the
Most acutely curved and usually shortest, the first rib is broad and flat,
internal border. The inferior surface is smooth and the anterior end is
its surfaces are superior and inferior, and its borders are internal and
larger than in any other rib.
external (see Fig. 53.9A). It slopes obliquely down and forwards to its
sternal end. The obliquity of the first rib accounts for the ingress of the
Vascular supply and innervation The first rib is supplied by the
pulmonary and pleural apices into the neck.
internal thoracic and superior intercostal arteries, drained by the inter-
The head of the first rib is small and round, and bears an almost
costal vein and innervated by the first intercostal nerve.
circular facet that articulates with the body of the first thoracic vertebra.
The neck is rounded and ascends posterolaterally, and the tubercle,
Ossification The first rib has a primary centre for the shaft, and sec-
wide and prominent, is directed up and backwards. Medially, an oval
ondary ossification centres for the head of the rib and the tubercle.
facet articulates with the transverse process of the first thoracic vertebra.
At the tubercle, the rib is bent, its head turned slightly down, and so
Second rib
the angle and tubercle coincide. The superior surface of the flattened
shaft is crossed obliquely by two shallow grooves, separated by a slight
ridge, which usually ends at the internal border as a small pointed The second rib is twice the length of the first and has a similar curvature.
projection, the scalene tubercle, to which scalenus anterior is attached. The non-articular area of its tubercle is small. The angle is slight and


bone and cartilage
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near the tubercle. The shaft is not twisted but at the tubercle is convex levator costae, longissimus thoracis and iliocostalis are attached to the
upwards, as in the first rib but less so. The external surface of the shaft medial half of the external surface, and serratus posterior inferior, latis-
is convex and superolaterally is marked centrally by a rough, muscular simus dorsi and external oblique are attached to its lateral half. The
impression that continues posteromedially towards the tubercle as a external intercostal muscle is attached along the upper border. These
narrow, roughened ridge. The internal surface, smooth and concave, attachments vary: those of the internal intercostal, levator costae and
faces inferomedially and there is a short costal groove posteriorly. erector spinae merge and those of latissimus dorsi, diaphragm and
The lower parts of the first two digitations of serratus anterior are external oblique may reach the costal cartilage. The lower limit of the
attached to a rough prominence that extends from just behind the pleural sac crosses in front of the rib, approximately at the point where
midpoint of the external surface (see Fig. 53.9B). The distinct lips of it is crossed by the lateral border of iliocostalis. Its lateral end is usually
the upper border are widely separated behind; scalenus posterior and below the line of costodiaphragmatic pleural reflection and is therefore
serratus posterior superior are attached to the outer lip in front of the not covered by pleura.
angle.
Vascular supply and innervation The tenth and eleventh ribs are
Vascular supply and innervation The blood supply of the second supplied by the posterior intercostal artery and branches from the mus-
rib is via the internal thoracic and superior intercostal arteries. Venous culophrenic artery. The twelfth rib is supplied by the subcostal artery.
drainage is via the superior intercostal vein, which drains into the bra- Venous drainage is via the posterior intercostal and subcostal veins,
chiocephalic vein, and the anterior intercostal veins, which drain into which in turn drain into the azygos system. There is additional drain-


the internal thoracic vein. The bone is innervated by branches of the age via the anterior intercostal veins (branches of the musculophrenic
first intercostal nerve. vein). The tenth and eleventh ribs are innervated by the corresponding
intercostal nerve, and the twelfth rib is innervated by the subcostal
Ossification The second rib is ossified from a primary centre for the nerve.
shaft, which appears near the angle late in the second month. The
secondary centres for the head and articular and non-articular parts of Ossification The tenth rib ossifies from a primary centre in the shaft
the tubercle appear about puberty, uniting to the shaft soon after the and secondary centres for the head and articular parts of the tubercle.
age of 20 years. The eleventh and twelfth ribs, without tubercles, have two centres each.
Tenth, eleventh and twelfth ribs Costal cartilages
The tenth rib has a single facet on its head that may articulate with the Costal cartilages are the persistent, ossified anterior parts of the carti-
intervertebral disc above, in addition to the upper border of the tenth laginous models in which the ribs develop. They are flat bars of hyaline
thoracic vertebra near its pedicle. The ninth and tenth ribs are usually cartilage that extend from the anterior ends of the ribs, and contribute
united anteriorly by a fibrous joint. However, the tenth rib may be free greatly to thoracic mobility and elasticity (see Fig. 53.8). The upper
in 35–70% (depending on ancestry), in which case it is pointed like the seven pairs join the sternum; the eighth to tenth articulate with the
eleventh and twelfth ribs. lower border of the cartilage above; and the lowest two have free,
The eleventh and twelfth ribs each have one large articular facet on pointed ends in the abdominal wall. They increase in length from the
the head but no neck or tubercle. Their pointed anterior ends are tipped first to the seventh, and then decrease to the twelfth. They diminish in
with cartilage. The eleventh rib has a slight angle and shallow costal breadth from first to last, like the intercostal spaces. The costal cartilages


groove. The twelfth rib has neither, is much shorter and slopes cranially are broad at their costal continuity and taper as they pass forwards. The
at its vertebral end. The internal surfaces of both ribs face slightly first and second are of even breadth and the sixth to eighth enlarge
upwards, more so in the twelfth. where their margins are in contact. The first descends a little, the second
Numerous muscles and ligaments are attached to the twelfth rib is horizontal and the third ascends slightly; the others are angulated
(Fig. 53.10). Quadratus lumborum and its anterior covering layer of and incline up towards the sternum or cartilage above, a little anterior
thoracolumbar fascia are attached to the lower part of its anterior to their ribs.
surface in its medial one-half to two-thirds; the upper part is related to Each costal cartilage has two surfaces, borders and ends. The anterior
the costodiaphragmatic pleural recess. The internal intercostal muscle surface is convex, facing anterosuperiorly. The sternoclavicular articular
(medially) and the diaphragm (laterally) are attached at or near the disc, costoclavicular ligament and subclavius are attached to the first
upper border. The lower border gives attachment to the middle lamella costal cartilage. Pectoralis major is attached to the medial aspect of the
of the thoracolumbar fascia and, lateral to quadratus lumborum, to the first six cartilages and the others are covered by the partial attachments
lateral arcuate ligament and posterior lamella of the thoracolumbar of the anterior abdominal muscles. The posterior surface is concave and,
fascia. The lumbocostal ligament is attached posteriorly, close to the really, posteroinferior. Sternothyroid is attached to the first cartilage,
head, connecting it to the first lumbar transverse process. The lowest transversus thoracis is attached to the second to sixth, and transversus
Fig. 53.10 The twelfth rib, left side. A, Anterior
aspect. Key: 1, attachment of internal intercostal
1 muscle; 2, attachment of costotransverse
ligament; 3, head; 4, area covered by pleura;
5, attachment of diaphragm; 6, line of pleural
2


reflection; 7, attachment of quadratus lumborum.
5
B, Posterior aspect. Key: 1, attachment of
latissimus dorsi; 2, attachment of external oblique;
3
3, attachment of serratus posterior inferior;
4, attachment of external intercostal muscle;
6 5, attachment of levator costae; 6, head;
4
A 7 7, attachment of erector spinae.
4
5
1
2
6
3 7
B


Chest wall and breast
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abdominis is attached to the lower six. The internal intercostal muscles
and external intercostal membranes are attached to the concave supe- Superior articular process
rior and convex inferior borders. The inferior borders of the fifth (some- Superior costal facet
times) and sixth to ninth cartilages project at points of greatest convexity.
Transverse costal facet
Oblong facets on these projections articulate with facets on slight pro-
jections from the superior borders of subjacent cartilages. The lateral Costotransverse foramen
end of each cartilage is continuous with its rib. The medial end of the
first is continuous with the sternum; those of the six succeeding carti-
lages are round and articulate with shallow costal notches on the lateral
Superior costotransverse
margins of the sternum; those of the eighth to tenth are pointed, each
ligaments
connected with the cartilage above; and those of the eleventh and
twelfth are pointed and free. With the exception of the fibrous synarth- Lateral costotransverse
rosis between the first rib and sternum, all these articulations are ligaments
synovial.
Anterior longitudinal
ligament
Costal cartilage ossification –
forensic radiology
Rib
Available with the Gray’s Anatomy e-book Vertebral body
Rib fractures
Intertransverse
ligament
Elastic recoil of the ribs that suspend the sternum may explain the rarity
Radiate ligament of
of sternal fractures. Despite their pliability, the ribs are much more
head of rib
frequently broken, the middle ribs being the most vulnerable. Because
traumatic stress is often the result of compression of the thorax, the Intervertebral discs
usual site of fracture is just in front of the angle, which is the weakest
point of the rib. Direct impact may fracture a rib at any point; the ends
of the broken bone may be driven inwards and potentially may injure
thoracic or upper abdominal viscera. Fig. 53.11 Ligaments of the vertebral column and costovertebral joints,
left lateral aspect. The lateral parts of the anterior longitudinal ligament
have been removed. (With permission from Waschke J, Paulsen F (eds),
JOINTS
Sobotta Atlas of Human Anatomy, 15th ed, Elsevier, Urban & Fischer,
2013.)


MANUBRIOSTERNAL JOINT
Joints of costal heads
The manubriosternal joint lies between the manubrium and sternal
body; it is usually a symphysis but it may be synovial, synchondrotic
or synostotic. It lies approximately 7 cm below the upper border of the Heads of typical ribs articulate with facets (often termed demifacets)
manubrium. The bony surfaces are covered by hyaline cartilage and on the margins of adjacent thoracic vertebral bodies and with the
connected by a fibrocartilage, which may ossify in the aged. Sometimes, intervertebral discs between them (Fig. 53.11). The first and tenth to
the central part of the disc is absorbed and the joint appears synovial. twelfth ribs articulate with a single vertebra by a simple synovial joint.
The manubriosternal joint is connected by a fibrous membrane envel- In the others, an intra-articular ligament bisects the joint, producing a
oping the entire bone. In occasional individuals over the age of 30 years, double synovial compartment, so the joint is classified as both com-
the manubrium is joined to the sternal body by bone but the interven- pound and complex. Often inaccurately described as plane, their articu-
ing cartilage may be only superficially ossified; ossification becomes lar surfaces are slightly ovoid and the upper and lower synovial
complete only in the aged. Early synostosis has been attributed to a articulations are obtusely angled to each other. The ligaments are cap-
persistent synchondrosis in place of a symphysis. In the newborn, union sular, radiate and intra-articular.
is by collagenous and elastic fibres, without chondrocytes.
Fibrous capsules The fibrous capsule connects the costal head to
Movements There is a small range of angulation between the longi- the circumference of the articular surface formed by an intervertebral
tudinal axes of the manubrium and body of the sternum, and limited disc and the demifacets of two adjacent vertebrae. Some of the upper
anteroposterior displacement. The powerful ligamentous attachments fibres traverse their intervertebral foramina to blend with the posterior


in this region mean that dislocation of the manubriosternal joint is rare, aspects of the intervertebral discs. The posterior fibres are continuous
although it may be associated with high-energy trauma. Dislocation is with the costotransverse ligaments.
most common when the joint is synovial, whereas synchondral and
synosteal types typically fracture through the manubrium. Radiate ligaments Radiate ligaments connect the anterior parts of
each costal head to the bodies of two vertebrae and their intervening
intervertebral disc. Each is attached to the head just beyond its articular
XIPHISTERNAL JOINT surface. Superior fibres ascend to the vertebral body above, inferior to
the body below. Intermediate fibres, shortest and least distinct, are
The joint between the xiphoid process and the body of the sternum horizontal and attached to the disc. The radiate ligament associated
process is a symphysis. It is usually transformed to a synostosis by the with the first rib is attached to the seventh cervical and first thoracic
fortieth year but sometimes remains unchanged, even in old age. vertebrae. In the joints of the tenth to twelfth ribs, which articulate with
single vertebrae, the radiate ligament is attached to the numbered ver-
tebra and the one above.
STERNOCLAVICULAR JOINT
Intra-articular ligament The intra-articular ligament is a short flat
The sternoclavicular joint is described in Chapter 48. band attached laterally to the crest between the costal articular facets
and medially to the intervertebral disc, dividing the joint. The ligament
is absent from the first and tenth to twelfth joints.
COSTOVERTEBRAL, STERNOCOSTAL AND
INTERCHONDRAL JOINTS Costotransverse joints
The heads of the ribs articulate with vertebral bodies (costocorporeal The facet of a costal tubercle articulates reciprocally with the transverse
joints); their necks and tubercles articulate with transverse processes process of its corresponding vertebra (Fig. 53.12). The eleventh and
(costotransverse joints). twelfth ribs lack this articulation. In the upper five or six joints, articular


Chest wall and breast
938.e1
35
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When present, marginal and central subperichondrial ossification pat-
terns seen on X-ray afford a relatively simple, rapid, inexpensive and
accurate means of identifying sex in completely or partially skeletonized
and unidentified human material, providing the subject is over 20 years
of age. The predictive ability of this technique lies in a range of 80–90%.
In males, the predictive ability of the marginal subperichondrial ossifi-
cation pattern is 75–80%. In females, the predictive ability for a central
subperichondrial ossification pattern is greater than 90%.


Joints
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Vertebral body
Radiate ligament of head of rib
Vertebral foramen
Joint between head of rib and vertebral body
Costotransverse ligament
Costotransverse ligament
Neck of rib
Costotransverse joint
Ligamentum flavum
Rib Tubercle of rib
Superior articular process Transverse process Lateral costotransverse ligament
Spinous process
Fig. 53.12 Costovertebral joints, superior aspect.
transverse process by a lumbocostal ligament in series with the superior
costotransverse ligaments.
Third thoracic vertebra Accessory ligament An accessory ligament is usually present. It lies
medial to the superior costotransverse ligament, and is separated from
it by the dorsal ramus of a thoracic spinal nerve and accompanying
vessels. These bands are variable in their attachments, but usually pass
from a depression medial to a costal tubercle to the inferior articular
process immediately above. Some fibres also pass to the base of the
transverse process.
Lateral costotransverse ligament The lateral costotransverse
ligament is short, thick and strong, and passes obliquely from the apex
of the transverse process to the rough non-articular part of the adjacent
costal tubercle. The ligaments of upper ribs ascend from their transverse
processes, and are shorter and more oblique than those of the lower
ribs, which descend.
Movements Costal heads are so firmly tied to vertebral bodies by
Eighth thoracic vertebra radiate and intra-articular ligaments that only slight gliding can occur.
Strong ligaments binding costal necks and tubercles to transverse proc-
esses also limit movements at costotransverse joints to slight gliding,
guided by the shape and direction of the articular surfaces (see Fig.
53.13). The facets on the tubercles of the upper six ribs are oval and
vertically convex, and fit corresponding concavities on the anterior
surfaces of transverse processes; consequently, up and down movements
Fig. 53.13 A section through the third to the ninth costotransverse joints. of tubercles involve rotation of costal necks about their long axes. The
Contrast the concave facets on the upper transverse processes with the facets on the seventh to tenth tubercles are almost flat and face down,


less curved facets on the lower transverse processes. medially and backwards; their opposing surfaces are on the upper
aspects of transverse processes and so, when these tubercles ascend, they
also move posteromedially. Both sets of joints move simultaneously
surfaces are reciprocally curved but below this they are flatter (Fig. and in the same directions; the costal neck therefore moves as if at a
53.13). Their ligaments are capsular, costotransverse, superior and single joint in which the two articulations form its ends.
lateral costotransverse, and accessory. In the upper six ribs, the neck moves slightly up and down but its
chief movement is one of rotation about its long axis, which means that
Fibrous capsule The fibrous capsule is thin and attached to articular downward rotation of its anterior aspect is associated with depression,
peripheries; it has a synovial lining. and upward rotation with elevation, of the shaft and anterior end of
the rib. In the seventh to tenth ribs, the neck ascends posteromedially
Costotransverse ligament The costotransverse ligament fills the or descends anterolaterally, increasing or diminishing the infrasternal
costotransverse foramen between the neck of the rib and its adjacent angle, respectively; slight rotation accompanies these movements.
corresponding transverse process. Its numerous short fibres extend back
Sternocostal joints
from the posterior rough surface on the neck to the anterior surface of
the transverse process. A costotransverse ligament is rudimentary or
absent in the eleventh and twelfth ribs. Costal cartilages articulate with small concavities on the lateral sternal
borders (chondrosternal articulations) (Fig. 53.14). Perichondrium
Superior costotransverse ligament The superior costotransverse and periosteum are continuous. The first sternocostal joint is an unusual
ligament has anterior and posterior layers. The anterior layer is attached variety of synarthrosis (fibrous) and is often inaccurately called a syn-
between the crest of the costal neck and lower aspect of the transverse chondrosis. The second to seventh costal cartilages articulate by syno-
process above, and blends laterally with the internal intercostal mem- vial joints, although articular cavities are often absent, particularly in


brane; it is crossed by the intercostal vessels and nerve. The posterior the lower joints. Fibrocartilage covers the articular surfaces and also
layer is attached posteriorly on the costal neck, ascending posteromedi- unites the costal cartilages and the sternum in those joints where
ally to the transverse process above, and blends laterally with the exter- cavities are absent. The seventh costosternal joint may be synovial or
nal intercostal muscle. The first rib has no such ligament. The shaft of ‘symphysial’. Ligaments involved are capsular, radiate sternocostal,
the twelfth rib, near its head, is connected to the base of the first lumbar intra-articular and costoxiphoid.


Chest wall and breast
940
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Fibrocartilaginous Sternothyroid Manubrium First costal cartilage
articular surfaces
Costochondral
junctions
Intra-articular
ligament
and two joint
cavities
Single
joint
cavities
Transversus thoracis Body Xiphoid Caval Central tendon of Internal intercostal
process opening diaphragm muscle
Fig. 53.15 The left transversus thoracis, exposed and viewed from its
Interchondral posterior aspect. The lower border of transversus thoracis is in contact
joint cavities
with the upper border of transversus abdominis in the interval between
(synovial)
the sternal and costal origins of the diaphragm. (With permission from
Interchondral ligaments Waschke J, Paulsen F (eds), Sobotta Atlas of Human Anatomy, 15th ed,
(syndesmoses)
Elsevier, Urban & Fischer, 2013.)
Fig. 53.14 Sternocostal and interchondral joints, anterior aspect.
Fibrous capsules Fibrous capsules surround the second to seventh Costochondral junctions
sternocostal joints. They are thin, blended with the sternocostal liga-
ments, and strengthened above and below by fibres that connect the Artificially separated from its rib, a costal cartilage has a rounded end
costal cartilages to the sternum. that fits a reciprocal depression in the rib. Periosteum and perichon-
drium are continuous across the costochondral junctions and the col-
Radiate sternocostal ligaments The radiate sternocostal liga- lagen of the osseous and cartilaginous matrices blend. No movement
ments are broad, thin bands that radiate from the anterior and posterior occurs at costochondral junctions.
surfaces of the sternal ends of the costal cartilages of the true ribs to the
corresponding sternal surfaces. Their superficial fibres intermingle with
adjacent ligaments above and below, with those of the opposite side MUSCLES
and with tendinous fibres of pectoralis major. Collectively, these tissues
form a thick fibrous membrane around the sternum that is more The intrinsic muscles of the chest wall are the intercostals, subcostales,


marked inferiorly. transversus thoracis, levatores costarum, serratus posterior and, occa-
sionally, sternalis. Scapular muscles and muscles connecting the upper
Intra-articular ligaments Intra-articular ligaments are constant limb, chest wall and vertebrae, i.e. trapezius, latissimus dorsi, rhom-
only between the second costal cartilages and sternum. The ligament boids major and minor, levator scapulae, pectorales major and minor,
associated with the second costal cartilage extends from the costal car- subclavius, supra- and infraspinatus, teres major and teres minor, are
tilage to the fibrocartilage uniting the manubrium and sternal body, described in detail in Chapter 48.
and is therefore intra-articular. Occasionally, the third sternal cartilage
is connected with the first and second sternal segments by a similar
ligament. Fibrocartilaginous strands may occur in the third and lower INTRINSIC CHEST WALL MUSCLES
joints. Articular cavities may be absent at any age.
Intercostal muscles
Costoxiphoid ligaments Costoxiphoid ligaments connect the ante-
The intercostal muscles are thin multiple layers of muscular and tendi-
rior and posterior surfaces of the seventh (and sometimes sixth) costal
nous fibres that occupy the intercostal spaces; their names are derived
cartilage to the same surfaces of the xiphoid process. They vary in length
from their spatial relationship, i.e. the external, internal and innermost
and breadth, and the posterior is less distinct.
intercostals (Fig. 53.15).
Movements Slight gliding movements, sufficient for ventilation, external intercostals
occur at sternocostal joints.
Eleven pairs of external intercostals extend from the tubercles of
the ribs, where they blend with the posterior fibres of the superior
Interchondral joints
costotransverse ligaments, almost to the costal cartilages, where each
continues forwards to the sternum as an aponeurotic layer, the exter-
Contiguous borders of the sixth to ninth costal cartilages articulate by nal intercostal membrane. Each muscle passes from the lower border


apposition of small oblong facets. Each articulation is enclosed in a thin of one rib to the upper border of the rib below; their fibres are
fibrous capsule, lined by synovial membrane with lateral and medial directed obliquely downwards and laterally at the back of the thorax,
interchondral ligaments. Sometimes the fifth cartilage, and less com- and downwards, forwards and medially at the front. In the upper
monly the ninth cartilage, articulate at their inferior borders with two or three spaces, they do not quite reach the ends of the rib, and
adjoining cartilages; this connection is usually effected by ligamentous in the lower two spaces, they extend to the free ends of the costal
fibres. Articulation between the ninth and tenth cartilages is never syno- cartilages. The external intercostals are thicker than the internal
vial and sometimes absent. intercostals.


Muscles
941
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Innervation External intercostals are supplied by the adjacent inter- Levatores costarum
costal nerves. Levatores costarum are strong bundles, 12 on each side, which arise
from the tips of the transverse processes of the seventh cervical and first
Action External intercostals are believed to act with the internal inter- to eleventh thoracic vertebrae. They pass obliquely downwards and
costals (Ch. 55). laterally, parallel with the posterior borders of the external intercostals.
Each is attached to the upper edge and external surface of the rib imme-
Internal intercostals diately below the vertebra from which it takes origin, between the
Eleven pairs of internal intercostals begin anteriorly at the sternum, in tubercle and the angle (levatores costarum breves). Each of the four
the interspaces between the cartilages of the true ribs, and at the anterior lower muscles divides into two fasciculi; one is attached as already
extremities of the cartilages of the ‘false’ ribs. Their greatest thickness described, and the other descends to the second rib below its origin
lies in this intercartilaginous or parasternal part. They continue back as (levatores costarum longi).
far as the posterior costal angles, where each is replaced by an aponeu-
rotic layer, the internal intercostal membrane, that is continuous pos- Innervation Levatores costarum are supplied by the lateral branches
teriorly with the anterior fibres of a superior costotransverse ligament, of the dorsal rami of the corresponding thoracic spinal nerves.
and anteriorly with the fascia between the internal and external inter-
costal muscles. Each muscle descends from the floor of a costal groove Action Levatores costarum elevate the ribs but their importance in
and adjacent costal cartilage, and inserts into the upper border of the ventilation is disputed. They are also said to act from their costal attach-
rib below; their fibres are directed obliquely, nearly at right angles to ments as rotators and lateral flexors of the vertebral column.
those of the external intercostal muscles.
serratus posterior superior
Innervation Internal intercostals are supplied by the adjacent inter- Serratus posterior superior (Fig. 53.16) is a thin quadrilateral muscle,


costal nerves. external to the upper posterior part of the thorax. It arises by a thin
aponeurosis from the lower part of the nuchal ligament, the spines of
Action Internal intercostals are believed to act with the external inter- the seventh cervical and upper two or three thoracic vertebrae, and their
costals (p. 974). supraspinous ligaments. It descends laterally and ends in four digita-
tions attached to the upper borders and external surfaces of the second,
Innermost intercostals third, fourth and fifth ribs, just lateral to their angles. It is superficial to
The innermost intercostals were once regarded as internal laminae of the thoracic part of the thoracolumbar fascia and deep to the rhom-
the internal intercostal muscles, and fibres in the two layers do coincide boids. The number of digitations can vary from three to six, and the
in direction. Each muscle is attached to the internal aspects of two muscle may even be absent.
adjoining ribs. They are insignificant, and sometimes absent, at the
highest thoracic levels but become progressively more substantial below Innervation Serratus posterior superior is innervated by the second,
this, typically extending through the middle two quarters of the lower third, fourth and fifth intercostal nerves.
intercostal spaces. Posteriorly, the innermost intercostals, in those
spaces where they are well developed, may come together with the cor- Action The attachments of serratus posterior superior clearly indicate
responding subcostales. The innermost intercostals are related inter- that it could elevate the ribs; its role in humans is uncertain.
nally to the endothoracic fascia and parietal pleura, and externally to
the intercostal nerves and vessels.
Innervation Innermost intercostals are supplied by the adjacent inter- Semispinalis capitis
costal nerves.
Mastoid process
Action Innermost intercostals are believed to act with the internal Splenius capitis
intercostals (Ch. 55).
Subcostales
Subcostales consist of muscular and aponeurotic fasciculi and are
usually well developed only in the lower part of the thorax. Each Serratus posterior superior Trapezius
descends from the internal surface of one rib, near its angle, to the


internal surface of the second or third rib below. Their fibres run parallel
to those of the internal intercostals and, like the innermost intercostals, Splenius cervicis
they lie between the intercostal vessels and nerves and the pleura.
Infraspinatus
Innervation Subcostales are supplied by the adjacent intercostal
nerves. Rhomboid major
Erector spinae
Action Subcostales depress the ribs.
Transversus thoracis
Latissimus dorsi
Transversus thoracis (triangularis sternae, sternocostalis) spreads over Serratus posterior
the internal surface of the anterior thoracic wall (see Fig. 53.15). It arises inferior
from the lower third of the posterior surface of the sternum, the xiphoid
process and the costal cartilages of the lower three or four true ribs near
their sternal ends. The fibres diverge and ascend laterally as slips that
pass into the lower borders and inner surfaces of the costal cartilages
External oblique
of the second, third, fourth, fifth and sixth ribs. The lowest fibres are
horizontal and are contiguous with the highest fibres of transversus
abdominis; the intermediate fibres are oblique; and the highest are
Gluteus medius
almost vertical. Transversus thoracis varies in its attachments, not only Erector spinae
between individuals but even on opposite sides of the same individual. tendon
Gluteus maximus
Like the innermost intercostals and subcostales, transversus thoracis
separates the intercostal nerves from the pleura.
Innervation Transversus thoracis is supplied by the adjacent intercos-
tal nerves.
Action Transversus thoracis draws down the costal cartilages to which
it is attached. Fig. 53.16 Superficial (extrinsic) muscles of the back.


Chest wall and breast
942
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serratus posterior inferior the sternal end of the clavicle and opposite the root of the thyrocervical
Serratus posterior inferior (Fig. 53.16) is a thin, irregularly quadrilateral trunk (see Fig. 51.2). It descends behind the first six costal cartilages,
muscle at the junction of the thoracic and lumbar regions. It arises from 1 cm from the lateral sternal border and divides at the level of the sixth
the spines of the lower two thoracic and upper two or three lumbar intercostal space into musculophrenic and superior epigastric branches.
vertebrae and their supraspinous ligaments by a thin aponeurosis that The superior epigastric artery is described in Chapter 61.
blends with the lumbar part of the thoracolumbar fascia. It ascends
laterally and its four digitations pass into the inferior borders and outer Relations At first, the internal thoracic artery descends anteromedially
surfaces of the lower four ribs, a little lateral to their angles. There may behind the sternal end of the clavicle, the internal jugular and brachio-
be fewer digitations and, in rare cases, the entire muscle may be absent. cephalic veins, and the first costal cartilage. As it enters the thorax, the
phrenic nerve crosses it obliquely from its lateral side, usually in front.
Innervation Serratus posterior inferior is innervated by ventral rami The artery then descends almost vertically to its bifurcation, lying
of the ninth, tenth, eleventh and twelfth thoracic spinal nerves. behind pectoralis major, the first six costal cartilages, external intercostal
membranes, internal intercostals and terminations of the upper six
Action Serratus posterior inferior draws the lower ribs downwards and intercostal nerves. It is separated from the pleura, down to the second
backwards, although possibly not in ventilation. or third cartilage, by a strong layer of fascia, and below this by trans-
versus thoracis. The artery is accompanied by a chain of lymph nodes
Sternalis and by venae comitantes that unite at about the third costal cartilage


Sternalis is an anatomical variation well known to anatomists but rela- into a single vein medial to the artery. Its intermediate branches are
tively unknown to clinicians and surgeons (Snosek et al 2014). The sternal, anterior intercostal and perforating.
muscle appears as a parasternal mass deep to the superficial fascia of
the anterior thoracic wall and superficial to the pectoral fascia overly- Sternal branches Sternal branches are distributed to transversus
ing pectoralis major. It may be a cord-like, flat band or irregular and thoracis, the periosteum of the posterior sternal surface and the sternal
flame-like in shape, is almost twice as commonly unilateral, and occurs red bone marrow. These branches, together with small branches of the
more often on the right side. Various attachment sites have been pericardiacophrenic artery, anastomose with branches of the posterior
described in an extensive anatomical literature, including the sternum, intercostal and bronchial arteries to form a subpleural mediastinal
inferior border of the clavicle, sternocleidomastoid fascia, pectoralis plexus.
major, and the upper ribs and their costal cartilages, all superiorly, and
the lower ribs and their costal cartilages, pectoralis major, the rectus Anterior intercostal branches Anterior intercostal arteries are
sheath and the external abdominal oblique aponeurosis, all inferiorly. distributed to the upper six intercostal spaces. They pass laterally along
The muscle occurs occasionally in the general population, but there is the borders of the space and anastomose with the posterior intercostal
great variation both within and between different geographic popula- arteries and their collateral branches (see Fig. 53.19). The anterior
tions. Its superficial location makes it an ideal candidate for utilization intercostals usually arise from the internal thoracic artery as single
as a muscular flap in plastic reconstruction of the head and neck vessels that promptly divide into two branches, one passing superiorly,
region. the other inferiorly within each intercostal space. Occasionally, one
The aetiology is unknown; sternalis may be an example of a much branch passes to the space above and one to the space below. (The


larger group of variations, including pectoralis minimus, pectoralis anterior intercostals may sometimes arise as two separate branches from
tertius, infraclavicularis and chondroepitrochlearis, that are thought to the internal thoracic artery.) The arteries lie at first between the pleura
be caused by a disturbance of the normal processes of pectoral muscle and the internal intercostals, then between the innermost and the inter-
development. nal intercostals (Fig. 53.18). They supply the intercostal muscles and
The relationship of sternalis to pectoralis major may cause a diag- send branches through them to the pectoral muscles, breast and skin.
nostic dilemma during breast surgery, mammography, computed tom-
ography and magnetic resonance imaging scans because its appearance Perforating branches Perforating branches traverse the upper five
mimics tumour pathology of the region. or six intercostal spaces with the anterior cutaneous branches of the
corresponding intercostal nerves. They pierce and supply pectoralis
Mechanism of thoracic cage movement major, and then curve laterally to become direct cutaneous vessels that
supply the skin. These cutaneous vessels provide the anatomical basis
for surgically raising the deltopectoral skin flap that is used for recon-
Breathing involves changing the thoracic volume by altering the vertical,
structing areas of missing tissue in the head and neck. The second
transverse and anteroposterior dimensions of the thorax (p. 974). The
to fourth branches supply the breast and become enlarged during
diaphragm is the key muscle in this process. Its muscle fibres descend
lactation.
from their relatively ‘high’ anterior sternocostal attachments steeply to
the central tendon and obliquely to their complex ‘low’ posterior
attachments (see Fig. 55.1). The central tendon is fixed: when the dia-
phragm contracts, it allows the lower ribcage to move inferiorly and
anteriorly without any change to the curvature of the diaphragm. The
intercostal muscles maintain the rigidity of the chest wall. The external
and internal intercostals, transversus thoracis, subcostales, levatores cos-
tarum, serratus posterior superior and serratus posterior inferior can
elevate or depress the ribs, and hence can act as accessory muscles of


ventilation.
External intercostal muscle
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE Intercostal vein
OF THE CHEST WALL
Intercostal artery
Internal intercostal muscle
ARTERIES
Intercostal nerve
Muscles of the thoracic wall receive their blood supply from the internal
thoracic artery, either directly or via the musculophrenic artery, the
Innermost intercostal muscle
superior intercostal artery, descending thoracic aorta, and the subcostal
and superior thoracic arteries. Additional contributions come from
vessels that supply the proximal muscles of the upper limb: namely, the
suprascapular, superficial cervical, thoraco-acromial, lateral thoracic
and subscapular arteries.
Internal thoracic artery Collateral branches
Fig. 53.18 Dissection of part of an intercostal space, external aspect,
The internal thoracic artery (internal mammary artery) arises inferiorly showing the position of the intercostal vessels and nerve and their
from the first part of the subclavian artery, approximately 2 cm above collateral branches relative to the intercostal muscles.


Chest wall and breast
942.e1
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The mammographic appearance of sternalis muscle is variable. Typi-
cally visible in the medial aspect of the breast on a craniocaudal (CC)
mammogram, it appears as a small soft tissue density/mass abutting
the chest wall. Its margins and shape are variable. Sternalis is not usually
seen on standard mediolateral oblique or mediolateral views.


Vascular supply and lymphatic drainage of the chest wall
943
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Musculophrenic artery The musculophrenic artery passes infero- Each artery crosses its intercostal space obliquely towards the angle
laterally behind the seventh to ninth costal cartilages, traverses the of the rib above and continues forwards in its costal groove. At first
diaphragm near the ninth, and ends near the last intercostal space. It between the pleura and internal intercostal membrane as far as the
anastomoses with the inferior phrenic and lower two posterior inter- costal angle, it passes between the internal intercostal and innermost
costal arteries and ascending branches of the deep circumflex iliac arter- intercostal muscles (see Fig. 53.18), anastomosing with an anterior
ies. Two anterior intercostal arteries branch from it for each of the intercostal branch from either the internal thoracic or musculophrenic
seventh to ninth intercostal spaces, and are distributed similarly to their artery. Each artery has a vein above and a nerve below, except in the
counterparts in the higher spaces. The musculophrenic artery also sup- upper spaces, where the nerve at first lies above the artery. The third
plies the lower part of the pericardium and the abdominal muscles. posterior intercostal artery anastomoses with the superior intercostal
artery and may provide the major supply to the second space. The lower
Clinical significance of the internal thoracic artery two arteries continue anteriorly into the abdominal wall, where they
anastomose with the subcostal, superior epigastric and lumbar arteries.
Available with the Gray’s Anatomy e-book Each posterior intercostal artery has dorsal, collateral, muscular and
cutaneous branches.
Superior intercostal artery Dorsal branch Each dorsal branch runs dorsally between the necks
of adjoining ribs; a vertebral body and superior costotransverse liga-
The superior intercostal artery arises from the costocervical trunk. It ment lie medial and lateral, respectively. Each dorsal branch gives off a
descends between the pleura and the necks of the first and second ribs, spinal branch that enters the vertebral canal via the intervertebral


and anastomoses with the third posterior intercostal artery. Crossing foramen and supplies the vertebra, spinal cord and meninges, anasto-
the neck of the first rib, it lies medial to the ventral branch of the first mosing with the spinal arteries above and below and with its contra-
thoracic spinal nerve, which it crosses at a lower level, and lateral to the lateral fellow. It then divides into a medial and a lateral dorsal
stellate ganglion. In the first space, it gives off the first posterior inter- musculocutaneous branch (occasionally, these arise separately from the
costal artery, which has a similar distribution to the lower posterior posterior intercostal artery rather than from a common trunk). The
intercostal arteries. It descends to become the second posterior inter- medial branch crosses a transverse process with the medial dorsal
costal artery, usually joining a branch from the third. The artery is not branch of a thoracic spinal nerve to supply spinalis, longissimus thora-
constant, and is more common on the right; when absent, it is replaced cis and an area of overlying skin. The lateral branch supplies longis-
by a direct branch from the aorta. simus thoracis and iliocostalis, and the medial aspects of latissimus
dorsi and trapezius, in addition to an area of overlying skin.
Posterior intercostal arteries
Collateral intercostal branch A collateral intercostal branch arises
near the costal angle and descends to the upper border of the subjacent
There are usually nine pairs of posterior intercostal arteries. They arise
rib, along which it courses to anastomose with an anterior intercostal
from the posterior aspect of the descending thoracic aorta and are dis-
branch of the internal thoracic or musculophrenic artery.
tributed to the lower nine intercostal spaces. Right posterior intercostal
arteries are longer because the aorta deviates to the left (Fig. 53.19);
Muscular branches Muscular branches supply the intercostal and
they cross the vertebral bodies behind the oesophagus, thoracic duct
pectoral muscles and serratus anterior, anastomosing with the superior
and azygos vein, right lung and pleura. Left posterior intercostal arteries
and lateral thoracic branches of the axillary artery. Lateral cutaneous


turn backwards on the vertebral bodies in contact with the left lung and
branches accompany the same branches of the thoracic spinal nerves.
pleura; the upper two are crossed by the left superior intercostal vein,
Mammary branches from the vessels in the second to fourth spaces
and the lower by the hemiazygos and accessory hemiazygos veins. The
supply the pectoral muscles, breast tissue and skin; they enlarge during
further course of the arteries is the same on both sides. The sympathetic
lactation.
trunk lies anterior to all of the arteries, and the splanchnic nerves
descend in front of the lower arteries.
Lateral cutaneous branch The lateral cutaneous branch is given
off in the posterior part of the intercostal space and travels anteriorly
Sternum Perforating branch
for a few centimetres with an accompanying vein and the lateral cutane-
ous branch of the equivalent intercostal nerve. This neurovascular
bundle pierces the intercostal muscles and emerges lower down between
the interdigitations of serratus anterior and external oblique. It divides
Internal thoracic
into anterior and posterior rami, which contribute to the blood supply
artery
Anterior intercostal of the skin of the lateral trunk; these vessels are less significant in the
branch upper three intercostal spaces.
Anterior
ramus Unnamed branches Other unnamed branches supply tissues of the
Outermost layer
attaching to shoulder Lateral thoracic wall, e.g. costal periosteum, bone and bone marrow of the ribs,
Muscle layers girdle cutaneous tissues of synovial and synarthrodial joints, and the parietal pleura.
branch
Intercostal muscles
Clinical significance of the posterior intercostal arteries
Vertebra Aorta Transversus thoracis Posterior
Collateral branch ramus
Posterior intercostal Available with the Gray’s Anatomy e-book
artery Intercostal artery
Iliocostalis VEINS
Rib Internal thoracic veins
The internal thoracic veins are venae comitantes of the inferior half of
the internal thoracic artery. Near the third costal cartilages, the veins
unite and ascend medial to the artery to end in their appropriate bra-
chiocephalic vein. Tributaries correspond to branches of the artery and


include a pericardiacophrenic vein. The internal thoracic veins have
Multifidus and Medial Lateral
semispinalis Dorsal cutaneous branches several valves.
Fig. 53.19 A schematic transverse section through a lower intercostal
Left superior intercostal vein
space to show the branches of a typical intercostal artery. The usual
branching arrangement of the dorsal cutaneous branch is shown to the
right of the spine and a common variant is shown to the left. (With The left superior intercostal vein drains the second and third (some-
permission from Cormack GC, Lamberty BGH 1994 The Arterial Anatomy times fourth) left posterior intercostal veins. It ascends obliquely for-
of Skin Flaps, 2nd ed. Edinburgh: Churchill Livingstone.) wards across the left aspect of the aortic arch, lateral to the left vagus


Chest wall and breast
943.e1
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retPahC
Right eleventh posterior intercostal Tip of the Cobra catheter in the origin of
artery opacified by contrast right eleventh posterior intercostal artery
Fig. 53.17 The internal thoracic vessels prepared for micro-anastomosis
beneath the third costal cartilage. The dissected internal thoracic artery A
(red arrow) and vein (blue arrow) are shown after removal of the right third
costal cartilage. These vessels are divided to provide recipient blood
supply for a free tissue transfer. ‘Blush’ or extravasation of contrast
indicates acute bleeding from a vessel
Platinum micro coils occluding the Superselective microcatheter which has been
artery to stop the bleeding inserted through the Cobra catheter to reach
The internal thoracic artery has a number of clinical uses but perhaps
more distally into the artery
most significantly is the vessel of choice for coronary artery bypass
grafting (Fig. 53.17). It has become a popular recipient vessel for free
flap transfers to the chest wall, principally for breast reconstruction
(Ninković et al 1995), and has largely superseded the thoracodorsal
vessels for this purpose. It is routinely accessed by removing a portion
of the third costal cartilage, although some surgeons prefer to dissect
the vessels between the ribs, with a rib-sparing approach (Parrett et al
2008, Malata et al 2011) or even utilizing the anterior perforating
branches as they pierce pectoralis major (Park et al 2003, Munhoz et al
2004). The anterior perforating branches form the vascular pedicles for
fasciocutaneous flaps raised from the chest wall that have been used for
many decades in head and neck reconstruction (Bakamjian et al 1971,
Neligan et al 2007). The superior epigastric artery is the main vascular
pedicle for the superiorly based rectus abdominis flap, a muscle or
myocutaneous flap useful in breast, sternal and chest wall reconstruc-
tion (Hartrampf et al 1982). During CT-guided lung and mediastinal
biopsies, the internal thoracic vessels must be avoided: exsanguination
has been reported with Trucut needle trauma. The approach must be at


least 2 cm lateral to the sternal margin. The vessels are not seen easily
on non-contrast fluoroscopic CT images.
Catheter embolization is an interventional radiology technique that can
be used to block branches of the posterior intercostal arteries when they
are bleeding, e.g. secondary to blunt trauma usually associated with rib
fractures, or when there is an abnormality of the vertebrae supplied by
the dorsal branch of the posterior intercostal artery. In such cases, the
posterior intercostal artery may be accessed by placing a catheter in the B
thoracic aorta, usually by puncturing the femoral artery in the groin. A
smaller catheter (referred to as a superselective catheter) may then be
placed in the posterior intercostal artery and embolic material (which Cobra catheter in the origin of the right
can be metallic coils or glue) injected to block the artery. This can cause eleventh posterior intercostal artery
cessation of bleeding in cases of trauma and provide pain relief when Fig. 53.20 A,B, Pre- and post-embolization images after selective
the vertebral body is infiltrated with tumour (Fig. 53.20). catherization of the right eleventh posterior intercostal artery.


Chest wall and breast
944
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nOItCes
and medial to the left phrenic nerve, to open into the left brachio- Lateral groups The lateral groups each contain two or three nodes,
cephalic vein. It usually receives the left bronchial veins, sometimes the and lie close to the point where the phrenic nerves enter the diaphragm.
left pericardiacophrenic vein, and connects inferiorly with the accessory On the right, some nodes lie within the fibrous pericardium anterior
hemiazygos vein. It may be seen on a chest X-ray as the ‘aortic nipple’, to the intrathoracic end of the inferior vena cava. Their afferents drain
not to be confused with a small lung nodule. the central diaphragm; those on the right also drain the convex surface
of the liver, and their efferents pass to the posterior mediastinal, para-
Posterior intercostal veins sternal and brachiocephalic nodes.
Posterior group The posterior group consists of a few nodes that lie
The posterior intercostal veins accompany their arteries in 11 pairs.
on the posterior aspect of the crura and connect with the lateral aortic
Approaching the vertebral column, each vein receives a posterior tribu-
and posterior mediastinal nodes.
tary that returns blood from the dorsal muscles and skin and the ver-
tebral venous plexuses. On both sides, the first posterior intercostal vein
Lymphatic drainage of deeper tissues
ascends anterior to the neck of the first rib, arching forwards above the
pleural dome to end in the ipsilateral brachiocephalic or vertebral vein.
On the right side, the second, third and often the fourth veins form a Collecting vessels of the deeper thoracic tissues include lymphatics that
right superior intercostal vein that joins the arch of the azygos vein. The drain the muscles attached to the ribs. Most end in axillary nodes but
lower spaces drain directly into the azygos vein. On the left side, the some from pectoralis major also drain to the parasternal nodes. Inter-
second, third and sometimes the fourth veins form a left superior inter- costal vessels drain the intercostal muscles and parietal pleura; those


costal vein. Veins from the fourth or fifth to eighth intercostal spaces from the anterior thoracic wall and pleura end in the parasternal nodes,
end in the accessory hemiazygos vein, and veins from the ninth to the and their posterior counterparts drain to intercostal nodes.
eleventh intercostal spaces drain into the hemiazygos vein. Vessels from the diaphragm form two plexuses, thoracic and abdom-
Posterior intercostal veins are so called to distinguish them from inal, which anastomose freely, especially in areas covered by pleura and
small anterior intercostal veins, which are tributaries of the internal peritoneum, respectively. The thoracic plexus unites with lymph vessels
thoracic and musculophrenic veins. draining the costal and mediastinal pleura. Its efferents are anterior,
draining to the anterior diaphragmatic nodes near the junctions of the
seventh rib and cartilage; middle, draining to nodes on the oesophagus
LYMPHATIC DRAINAGE and around the end of the inferior vena cava; and posterior, draining
to nodes around the aorta at the point where it leaves the thorax. The
Superficial lymphatic vessels of the thoracic wall ramify subcutaneously abdominal plexus anastomoses with the hepatic lymphatics and periph-
and converge on the axillary nodes (see Fig. 53.22). Those superficial erally with those of the subperitoneal tissue. Efferents from its right half
to trapezius and latissimus dorsi unite to form 10 or 12 trunks, which end in a group of nodes on the inferior phrenic artery, or in the right
end in the subscapular nodes. Those in the pectoral region, including lateral aortic nodes. Those from the left half of the abdominal diaphrag-
vessels from the skin covering the periphery of the breast and its subare- matic plexus pass to the pre-aortic, lateral aortic and terminal oesopha-
olar plexus, run back, collecting those superficial to serratus anterior, to geal nodes.
reach the pectoral nodes. Vessels near the lateral sternal margin pass
between the costal cartilages to the parasternal nodes and anastomose
INNERVATION OF THE CHEST WALL


across the sternum, providing a route for contralateral nodal spread in
medially located breast carcinoma. A few vessels from the upper pecto-
THORACIC VENTRAL SPINAL RAMI
ral region ascend over the clavicle to the inferior deep cervical nodes.
Lymph from the deeper tissues of the thoracic walls drains mainly to
the parasternal, intercostal or diaphragmatic nodes. There are 12 pairs of thoracic ventral rami. The upper 11 lie between
the ribs (intercostal nerves) and the twelfth lies below the last rib (sub-
Parasternal (internal thoracic) nodes costal nerve). Each is connected with the adjoining ganglion of the
sympathetic trunk by grey and white rami communicantes; the grey
ramus joins the nerve proximal to the point at which the white ramus
There are four or five parasternal nodes along each internal thoracic
leaves it (Fig. 53.21). Intercostal nerves are distributed primarily to the
artery at the anterior ends of the intercostal spaces. They drain afferents
thoracic and abdominal walls. The first two nerves supply fibres to the
from the breast, deeper structures of the supra-umbilical anterior
abdominal wall, the superior hepatic surface (through a small group of
nodes behind the xiphoid process) and deeper parts of the anterior
Anterior cutaneous branch
thoracic wall. Their efferents usually unite with those from the tracheo-
bronchial and brachiocephalic nodes to form the bronchomediastinal
trunk. The latter may open on either side, directly into the jugulosub-
clavian junction, into either great vein near the junction, the right External intercostal
subclavian trunk or lymphatic duct, or the thoracic duct on the left.
Internal thoracic Internal intercostal
Intercostal nodes artery
Pleura Innermost intercostal
Intercostal nodes occupy the intercostal spaces near the heads and necks
of the ribs. They receive deep lymph vessels from the posterolateral
aspects of the chest wall and breast, some of which are interrupted by Lateral cutaneous
branch
small lateral intercostal nodes. Efferents of nodes in the lower 4–7
spaces unite into a trunk that descends to the abdominal confluence of
Recurrent nerve


lymph trunks or to the start of the thoracic duct. Efferents of nodes in to vertebral canal Sympathetic ganglion
the left upper spaces end in the thoracic duct; those of the right upper Intercostal nerve
(ventral ramus)
spaces end in one of the right lymph trunks. Rami
communicantes
Diaphragmatic nodes
Subcostalis
Located on the thoracic surface of the diaphragm, these nodes are
arranged in anterior, right and left lateral, and posterior groups.
Dorsal ramus Internal intercostal
Anterior group The anterior group consists of two or three small membrane
nodes behind the base of the xiphoid process, draining the convex
hepatic surface, and one or two nodes on each side near the junction
of the seventh rib and cartilage, which receive anterior lymph Medial branch Lateral branch Superior costotransverse ligament
vessels from the diaphragm. The anterior group drains to the parasternal Fig. 53.21 The course of a typical intercostal nerve. The muscular and
nodes. the collateral branches are not shown.


breast
945
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upper limb in addition to their thoracic branches, the next four supply extends from the midline laterally for 10 or 12 cm (rectus abdominis
only the thoracic wall, and the lower five supply both thoracic and syndrome).
abdominal walls. The subcostal nerve is distributed to the abdominal
wall and the gluteal skin. Communicating branches link the intercostal Twelfth thoracic ventral ramus
nerves posteriorly in the intercostal spaces, and the lower five nerves (subcostal nerve)
communicate freely in the abdominal wall.
The ventral ramus of the twelfth thoracic nerve (subcostal nerve) is
First to sixth thoracic ventral rami
larger than the others and gives a communicating branch to the first
lumbar ventral ramus (sometimes termed the dorsolumbar nerve). Like
The first thoracic ventral ramus divides unequally: a large branch the intercostal nerves, it soon gives off a collateral branch and then
ascends across the neck of the first rib, lateral to the superior intercostal accompanies the subcostal vessels along the inferior border of the
artery, to enter the brachial plexus, and a smaller branch (the first inter- twelfth rib, passing behind the lateral arcuate ligament and kidney, and
costal nerve) runs in the first intercostal space and terminates as the in front of the upper part of quadratus lumborum. It perforates the
first anterior cutaneous nerve of the thorax. A lateral cutaneous branch aponeurosis of the origin of transversus abdominis and passes forwards
pierces the chest wall anterior to serratus anterior and supplies the axil- between that muscle and internal oblique, to be distributed in the same
lary skin; it may communicate with the intercostobrachial nerve and manner as the lower intercostal nerves. The subcostal nerve connects
sometimes joins the medial cutaneous nerve of the arm. The first tho- with the iliohypogastric nerve of the lumbar plexus and sends a branch
racic ramus often receives a connecting ramus from the second, which to pyramidalis. Its lateral cutaneous branch pierces the internal and


ascends in front of the neck of the second rib. external oblique muscles and supplies the lowest slip of the latter. It
The second to sixth thoracic ventral rami pass forwards in their usually descends over the iliac crest 5 cm behind the anterior superior
intercostal spaces below the intercostal vessels. Posteriorly, they lie iliac spine (see Fig. 61.5) and is distributed to the anterior gluteal skin;
between the pleura and external intercostal membranes, but they run some filaments reach as low as the greater trochanter of the femur.
mainly between the internal intercostals and the subcostales/innermost
intercostals. Near the sternum, they cross anterior to the internal tho-
THORACIC DORSAL SPINAL RAMI
racic vessels and transversus thoracis, pierce the internal intercostals,
the external intercostal membranes and pectoralis major, and terminate
as the anterior cutaneous nerves of the thorax. The second anterior Thoracic dorsal rami pass backwards close to the vertebral zygapophy-
cutaneous nerve may be connected to the medial supraclavicular nerves sial (facet) joints and divide into medial and lateral branches. The
of the cervical plexus, and twigs from the sixth intercostal nerve supply medial branch emerges between the joint and the medial edge of
abdominal skin in the upper part of the infrasternal angle. the superior costotransverse ligament and intertransverse muscle. The
lateral branch runs in the interval between the ligament and the muscle
Branches Numerous slender muscular filaments supply the intercos- before inclining posteriorly on the medial side of levator costae.
tals, serratus posterior superior and transversus thoracis. Anteriorly, Medial branches of the upper six thoracic dorsal rami pass between
some cross the costal cartilages from one intercostal space to another. and supply semispinalis thoracis and multifidus; they then pierce the
Each intercostal nerve gives off a collateral and a lateral cutaneous rhomboids and trapezius and reach the skin near the vertebral spines
branch before it reaches the angle of the adjoining ribs (see Fig. 53.21). (see Fig. 45.8). Medial branches of the lower six thoracic dorsal rami


The collateral branch follows the inferior border of its space in the same are distributed mainly to multifidus and longissimus thoracis; occasion-
intermuscular plane as the main nerve, which it may rejoin before it is ally, they give filaments to the skin in the median region. Lateral
distributed as an additional anterior cutaneous nerve. The lateral cuta- branches increase in size from above downwards. They run through or
neous branch accompanies the main nerve a little way and then pierces deep to longissimus thoracis to the interval between it and iliocostalis
the intercostal muscles obliquely. With the exception of the lateral cervicis, supplying these muscles and levatores costarum; the lower five
cutaneous branches of the first and second intercostal nerves, each or six also give off cutaneous branches, which pierce serratus posterior
divides into anterior and posterior rami that subsequently pierce ser- inferior and latissimus dorsi in line with the costal angles. The lateral
ratus anterior. Anterior branches run forwards over the border of pec- branches of a variable number of the upper thoracic rami also supply
toralis major to supply the overlying skin; those of the fifth and sixth the skin. The lateral branch of the twelfth dorsal ramus sends a filament
also supply twigs to a variable number of upper digitations of external medially along the iliac crest and then passes inferiorly to innervate the
oblique. Posterior branches run backwards and supply the skin over the skin of the anterior part of the gluteal region.
scapula and latissimus dorsi. Medial cutaneous branches of the thoracic dorsal rami descend for
The lateral cutaneous branch of the second intercostal nerve is the some distance close to the vertebral spines before reaching the skin.
intercostobrachial nerve (see Fig. 48.34). It crosses the axilla to gain the Lateral branches descend for a considerable distance, which may be as
medial side of the arm and joins a branch of the medial cutaneous nerve much as the breadth of four ribs, before they become superficial, e.g.
of the arm. It then pierces the deep fascia of the arm, and supplies the the branch of the twelfth thoracic ramus reaches the skin only a little


skin of the upper half of the posterior and medial parts of the arm, way above the iliac crest.
communicating with the posterior cutaneous branch of the radial nerve.
Its size is in inverse proportion to the size of the medial cutaneous BREAST
nerve. A second intercostobrachial nerve often branches off from the
anterior part of the third lateral cutaneous nerve and sends filaments
The breasts form a secondary sexual feature of females and are a source
to the axilla and the medial side of the arm.
of nutrition for the neonate. In young adult females, each breast is a
Seventh to eleventh thoracic ventral rami rounded eminence largely lying within the superficial fascia anterior to
the upper thorax but spreading laterally to a variable extent (Figs 53.22,
53.23A). Breast shape and size depend on genetic, racial and dietary
The ventral rami of the seventh to eleventh thoracic nerves are contin-
factors and on the age, parity and menopausal status of the individual.
ued anteriorly from the intercostal spaces into the abdominal wall; their
Breasts may be hemispherical, conical, variably pendulous, piriform or
further course is described in Chapter 61.
thin and flattened. In the adult female, the base of the breast, i.e. its
attached surface, extends vertically from the second or third to the sixth
Lesions of the intercostal nerves
rib, and in the transverse plane from the sternal edge medially almost
to the mid-axillary line laterally. The superolateral quadrant is pro-
Subluxation of the interchondral joints between the lower costal carti- longed towards the axilla along the inferolateral edge of pectoralis
lages may trap the intercostal nerves, causing referred abdominal pain. major, from which it projects a little, and may extend through the deep
The dorsal cutaneous branch of an intercostal nerve can become fascia up to the apex of the axilla (the axillary tail of Spence). The trunk
entrapped as it penetrates the fascia of erector spinae. This produces an superficial fascial system splits to enclose the breast to form the anterior
area of numbness, usually with painful paraesthesia, which extends and posterior lamellae. Posterior extensions of the superficial fascial


approximately 10 cm from the midline laterally and 10 cm in length system connect the breast to the pectoralis fascia, part of the deep fascial
(notalgia paraesthetica); the area between the medial edge of the system. The inframammary crease is a zone of adherence of the super-
scapula and the spine is commonly affected. The anterior cutaneous ficial fascial system to the underlying chest wall at the inferior crescent
branches of the intercostal nerves can also become entrapped as they of the breast.
penetrate the fascia of rectus abdominis, and this produces an area of The breast lies on the deep pectoral fascia, which in turn overlies
numbness on the abdomen, usually with painful paraesthesia, which pectoralis major and serratus anterior superiorly and external oblique


Chest wall and breast
946
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Internal thoracic artery
Pectoral branch of
thoraco-acromial artery Pectoralis major
Apical axillary nodes
Central axillary nodes
Secretory lobule
Lateral thoracic artery
Suspensory ligament
Lactiferous duct
Lateral axillary nodes
Pectoral axillary nodes
Lactiferous sinus
Axillary tail Retromammary space
Parasternal nodes
Lymphatic and venous drainage
passes from lateral and superior
part of the breast into axilla
Mammary branch of
internal thoracic artery
Areola Lymphatic and venous
drainage passes from medial part
of the breast parasternally
Fig. 53.22 The relations of the breast. (With permission from Drake, RL, Vogl, AW, Mitchell, A (eds), Gray’s Anatomy for Students, 2nd ed, Elsevier,
Churchill Livingstone. Copyright 2010.)
and its aponeurosis inferiorly, as the latter forms the anterior wall of The skin covering the nipple and the surrounding areola (the disc
the rectus sheath. Between the breast and the deep fascia, the loose of skin that circles the base of the nipple) has a convoluted surface. It
connective tissue in the ‘submammary space’ allows the breast some contains numerous sweat and sebaceous glands that open directly on
degree of movement on the deep pectoral fascia. Advanced mammary to the skin surface. The oily secretion of these specialized sebaceous
carcinoma may cause tethering or fixation of the breast to the underly- glands acts as a protective lubricant and facilitates latching of the
ing musculature. Occasionally, small projections of glandular tissue neonate during lactation; the glands are often visible in parous women,
may pass through the deep fascia into the underlying muscle in normal arranged circumferentially as small elevations, Montgomery’s tubercles,
subjects. around the areola close to the margin. Other areolar glands, intermedi-
ate in structure between mammary and sweat glands, become enlarged
in pregnancy and lactation as subcutaneous tubercles. The sebaceous
NIPPLE AND AREOLA glands of the areola are not usually associated with hair follicles. The
skin of the nipple and areola is rich in melanocytes and is therefore


The nipple projects from the centre of the breast anteriorly (Fig. typically darker than the skin covering the remainder of the breast;
53.23A–C). It may be cylindrical and rounded, hemispherical or flat- further darkening occurs during the second month of pregnancy, and
tened, depending on the effects of developmental, nervous or hormonal subsequently persists to a variable degree.
factors and external temperature on the erectile properties of the subare-
olar muscle of the nipple. The level of the nipple varies widely. In
females, its site is dependent on the size and shape of the breasts; it SOFT TISSUE
overlies the fourth intercostal space in most young women. In the male,
the nipple is usually sited in the fourth intercostal space in the mid- The breasts are composed of lobes that contain a network of glandular
clavicular line. In the young adult of either sex, the nipples are usually tissue consisting of branching ducts and terminal secretory lobules in
positioned 20–23 cm from the suprasternal notch in the mid-clavicular a connective tissue stroma (see Fig. 53.30). The terminal duct lobular
line and 20–23 cm apart in the horizontal plane. With increasing age unit is the functional milk secretory component of the breast; pathologi-
and parity, female breasts adopt a more ptotic shape and the position cally, it gives rise to primary malignant lesions within the breast.
of the nipple drops to the level of the inframammary crease or below. Although the lobes are usually described as discrete territories, they
In the nulliparous, the nipple is pink, light brown or darker, depending intertwine in three dimensions and merge at their edges; they cannot
on the general melanization of the body. Occasionally, the nipple may be distinguished during surgery. The connective tissue stroma that sur-
not evert during prenatal development and it remains permanently rounds the lobules is dense and fibrocollagenous, whereas intralobular
retracted (see below). connective tissue has a loose texture that allows the rapid expansion of


breast
947
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A B
Pectoralis
minor
Pectoralis
Axillary tail
major
Pectoral
Non-lactating
fascia
breast
Suspensory
Edge of
ligament
pectoralis
major deep Submammary
to breast space
Deep layers
of
Superficial fascia
Areola Adipose tissue
Nipple
Rib
Possible
extensions
of mammary Breast during Secretory lobule
tissue (posterior lactation containing alveoli
and medial)
C D
S
Sebaceous gland
Circular smooth muscle
Lactiferous duct
L
S S
Accessory gland L
(tubercle of Montgomery)
Areola
Fig. 53.23 A, The structure of the breast. B, Changes in the breast during lactation. C, A section of the nipple. D, A cross-section of the nipple. There is
a corrugated layer of stratified squamous keratinized epithelium over the nipple surface; 20 or more lactiferous ducts (L) open on to the surface;
sebaceous glands (S) are deep to the epidermis. (D, With permission from Dr JB Kerr, Monash University, from Kerr JB 1999 Atlas of Functional
Histology. London: Mosby.)
secretory tissue during pregnancy (see Fig. 53.30B). Fibrous strands or lateral border of pectoralis major to supply the lateral aspect of the
sheets consisting of condensations of connective tissue extend between breast) and the subscapular artery. The internal thoracic artery supplies
the layer of deep fascia that covers the muscles of the anterior chest wall perforating branches to the anteromedial part of the breast. The second
and the dermis. These suspensory ligaments (of Astley Cooper) are often to fourth anterior intercostal arteries supply perforating branches more
well developed in the upper part of the breast and support the breast laterally in the anterior thorax. The second perforating artery is usually
tissue, helping to maintain its non-ptotic form. Elsewhere in the normal the largest and supplies the upper region of the breast, the nipple, areola
breast, fibrous tissue surrounds the glandular components and extends and adjacent breast tissue.
to the skin and nipple, assisting the mechanical coherence of the gland.


The interlobar stroma contains variable amounts of adipose tissue, Veins
which is responsible for much of the increase in breast size at puberty.
Blood drains from the circular venous plexus around the areola and
VASCULAR SUPPLY AND LYMPHATIC DRAINAGE from the glandular tissue of the breast into the axillary, internal thoracic
and intercostal veins via veins that accompany the corresponding arter-
Arteries ies. Individual variation is common.
Lymphatic drainage
The breasts are supplied by branches of the axillary, internal thoracic
and some intercostal arteries. The axillary artery supplies blood via the
superior thoracic artery, the pectoral branches of the thoraco-acromial The lymphatic flow of the breast is of great clinical significance because
artery, the lateral thoracic artery (via branches that curve around the metastatic dissemination occurs principally by the lymphatic routes


Chest wall and breast
948
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nOItCes
(the breasts are the site of malignant change in as many as 1 in 8 apical axillary nodes, sometimes interrupted by the infraclavicular
women). The dominant lymphatic drainage of the breast is derived nodes or by small, inconstant, interpectoral nodes. Most of the remain-
from the dermal network. The breast lymphatics branch extensively and der drain to parasternal nodes from the medial and lateral parts of the
do not contain valves; lymphatic blockage through tumour occlusion breast; they accompany perforating branches of the internal thoracic
may therefore result in reverse blood flow through the lymphatic chan- artery. Lymphatic vessels occasionally follow lateral cutaneous branches
nels. The direction of lymphatic flow within the breast parallels the of the posterior intercostal arteries to the intercostal nodes.
major venous tributaries and enters the regional lymph nodes via the
Axillary surgery in breast cancer
extensive periductal and perilobular network of lymphatic channels.
Most of these lymphatics drain into the axillary group of regional Axillary lymph node dissection may be performed because the presence
lymph nodes either directly or through the retro-areolar lymphatic of metastases within axillary lymph nodes has strong prognostic signifi-
plexus (see Fig. 48.48). Dermal lymphatics also penetrate pectoralis cance and might influence decisions on adjuvant therapy. However,
major to join channels that drain the deeper parenchymal tissues, and axillary lymph node dissection can lead to chronic postoperative prob-
then follow the vascular channels to terminate in the subclavicular lems such as pain, seroma formation, reduced mobility of the arm,
lymph nodes. impaired sensation and lymphoedema. The vessels and nerves have to
Lymphatics from the left breast ultimately terminate in the thoracic be carefully identified at surgery as anatomical landmarks.
duct and, subsequently, the left subclavian vein. On the right, the lym-
Lymphatic drainage in breast cancer and
phatics ultimately drain into the right subclavian vein near its junction
with the internal jugular vein. Part of the medial side of the right breast role of sentinel lymph node biopsy
drains towards the internal thoracic group of lymph nodes. The internal Lymphatic mapping with sentinel lymph node biopsy has become an


thoracic chain may drain inferiorly via the superior and inferior epigas- important technique in the staging of patients with early breast cancer.
tric lymphatic routes to the groin. Connecting lymphatics across the A radiolabelled colloid is injected into either the subareolar tissue of
midline may provide access of lymphatic flow to the opposite axilla. the index quadrant of the breast or the peritumoral and intradermal
Axillary nodes receive more than 75% of the lymph from the breast tissue overlying the primary breast cancer. At the time of surgery, a vital
(Fig. 53.24). There are 20–40 nodes, grouped artificially as pectoral blue dye is injected after general anaesthesia is established. The combi-
(anterior), subscapular (posterior), central and apical. Surgically, the nation of radioisotope and dye provides the most accurate means of
nodes are described in relation to pectoralis minor. Those lying below localizing the sentinel node (Tanis et al 2001). The latter represents the
pectoralis minor are the low nodes (level 1), those behind the muscle first draining node of the axilla and is surgically removed for careful
are the middle group (level 2), while the nodes between the upper histopathological analysis to detect the presence of metastases.
border of pectoralis minor and the lower border of the clavicle are the
upper or apical nodes (level 3). There may be one or two other nodes
between pectoralis minor and major; this interpectoral group of nodes INNERVATION
are also known as Rotter’s nodes. Efferent vessels directly from the
breast pass round the anterior axillary border through the axillary fascia The breast is innervated by anterior and lateral branches of the fourth
to the pectoral lymph nodes; some may pass directly to the subscapular to sixth intercostal nerves, which carry sensory and sympathetic efferent
nodes. A few vessels pass from the superior part of the breast to the fibres. The nipple is supplied from the anterior branch of the lateral
cutaneous branch of T4, which forms an extensive plexus within the
nipple; its sensory fibres terminate close to the epithelium as free
Internal thoracic chain
endings, Meissner corpuscles and Merkel disc endings. These are essen-
Supraclavicular nodes


tial in signalling suckling to the central nervous system. Secretory activi-
Apical group ties of the gland are largely controlled by ovarian and hypophysial
Infraclavicular nodes hormones rather than by efferent motor fibres. The areola has fewer
Lateral group sensory endings.
MICROSTRUCTURE
The microstructure of breast tissue varies with age, time in the menstrual
cycle, pregnancy and lactation. The following description relates to the
mature, resting breast. For most of their lengths, the ducts are lined by
columnar epithelium (Fig. 53.25A). In the larger ducts, this is two cells
thick but, in the smaller ones, only a single layer of columnar or cuboi-
dal cells is present. The bases of these cells are in close contact with
numerous myoepithelial cells of ectodermal origin, similar to those of
certain other glandular epithelia (see Figs 2.3, 2.4, 53.30A). Myoepithe-
lial cells are so numerous that they form a distinct layer surrounding
the ducts and presumptive alveoli, and give the epithelium a bilayered
Central group appearance.
Lactiferous ducts draining each lobe of the breast pass through the
Subscapular group
nipple and open on to its tip as 15–20 orifices. Near its orifice, each of
these ducts is slightly expanded as a lactiferous sinus, which, in the
lactating breast, is further dilated by the presence of milk. Each lactifer-
ous duct is therefore connected to a system of ducts and lobules, sur-
Pectoral group
rounded by connective tissue stroma, collectively forming a lobe of the
breast. Lobules consist of the portions of the glands that have secretory
potential. Their structure varies according to hormonal status. In the
mature resting breast, each lobule consists of a cluster of blind-ended,
Cutaneous collecting branched ductules (Fig. 53.25B), whose termini lack mature terminal
trunks from alveoli (acini), which are the sites of milk secretion in the lactating
thoracic wall breast (see Fig. 53.30B). The stratified cuboidal lining is replaced by


keratinized stratified squamous epithelium, continuous with the epi-
dermis, close to the openings of the lactiferous ducts on the nipple.
Subareolar plexus Shed squames may sometimes block the duct apertures in the non-
pregnant breast.
Internally, the nipple is composed mostly of collagenous dense con-
nective tissue and contains numerous elastic fibres that wrinkle the
overlying skin. Deep to the nipple and areola, bundles of smooth
Drainage to parasternal nodes muscle cells are arranged radially and circumferentially within the
Fig. 53.24 Lymph vessels of the breast and the draining axillary and connective tissue and are thought to be remnants of the panniculus
supraclavicular nodal groups. carnosus. Their contraction, induced by cold or tactile stimuli (e.g. in


Chest wall and breast
948.e1
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If the histopathological results prove negative, the morbidity associ-
ated with axillary dissection can be avoided. In women who are found
to have metastases to the axillary nodal group, axillary completion dis-
section or radiotherapy is offered. The majority of sentinel nodes are
found in the low axilla (level 1). Higher-level ‘skip’ nodes are involved
in 5–10% of cases. Occasionally, the sentinel node is identified in an
extra-axillary position, either within the breast parenchyma as an
intramammary lymph node, or as an internal thoracic lymph node or
in the supraclavicular fossa.


breast
949
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6 weeks i.u. 12 weeks i.u.
Epithelium Mammary pit
Late fetus Neonate
Lactiferous duct Secretory lobule
Fig. 53.27 Early development of breast epithelium. Abbreviation: i.u.,
intrauterine.
suckling), causes erection of the nipple and wrinkling of the surround-
ing areola.
BREAST CANCER
Available with the Gray’s Anatomy e-book
DEVELOPMENT
A
The epithelial/mesenchymal interactions that will give rise to the glan-
dular tissue of the breast in both sexes can first be seen at about the
fifth or sixth week, when two ventral bands of thickened ectoderm, the
mammary ridges or milk lines, extend from the axilla to the inguinal
region. Usually, invagination of the thoracic mammary bud occurs by
day 49, and the remaining mammary line involutes.
The thoracic ectodermal ingrowths branch into 15–20 solid buds of
ectoderm that will become the lactiferous ducts and their associated
lobes of alveoli in the fully formed gland. They are surrounded by
somatopleuric mesenchyme that forms the connective tissue, fat and
vasculature that is invaded by the mammary nerves. Continued cell
proliferation, elongation and further branching produce the alveoli and
define the duct system. Nipple formation begins at day 56, primitive
ducts (mammary sprouts) develop at 84 days, and canalization occurs
at about the 150th day. During the last 2 months of gestation, the ducts
become canalized and the epidermis at the point of original develop-
ment of the gland forms a small mammary pit, into which the lactifer-
ous tubules open (Fig. 53.27). Perinatally, the nipple is formed by
mesenchymal proliferation. Should this process fail, the ducts open
into shallow pits. Rarely, the nipple may not develop (athelia), a phe-
nomenon that occurs more commonly in accessory breast tissue.
At birth, the breasts have reached a similar developmental stage in
both sexes, and the combination of fetal prolactin and maternal oes-


trogen may give rise to transient hyperplasia and secretion of ‘witch’s
milk’. In males, the breasts normally remain undeveloped whereas in
females at puberty, in late pregnancy and during the period of lactation,
they undergo further, hormone-dependent developmental changes. The
female breast is a unique organ in that it remains in a rudimentary (i.e.
fetal) form until puberty, at which time its development continues
B
under the influence of sex hormones. The adult form is reached in late
adolescence, i.e. the breast is then able to function as a milk-producing
Fig. 53.25 A, A glandular lobule surrounded by collagenous interlobular
organ. At menopause, the breast involutes into a predominantly fatty
connective tissue in the mature resting breast. A terminal duct (bottom
organ with minimal glandular parenchyma.
right) branches extensively to terminate in rudimentary acini. B, The
rudimentary acini shown at higher magnification, surrounded by fibrous
Accessory breast tissue and nipples
and adipose connective tissue. (A, With permission from Young B,
Heath JW 2000 Wheater’s Functional Histology. Edinburgh: Churchill
Livingstone. B, Courtesy of Mr Peter Helliwell and the late Dr Joseph Polymastia (supernumerary breasts) and polythelia (supernumerary
Mathew, Department of Histopathology, Royal Cornwall Hospitals nipples) may develop in males and females anywhere along the length
Trust, UK.) of the mammary ridges (milk lines; Fig. 53.28). Conversely, breast
tissue may not develop at all (amastia), or there may be nipple develop-
ment but no breast tissue (amazia). Supernumerary breast development


Chest wall and breast
949.e1
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Breast cancer is a common disease, particularly in postmenopausal nodes. In an implant-based immediate breast reconstruction, a tissue
women (see Fentiman 1993). Each year, in the United Kingdom, there expander is placed beneath the musculofascial plane consisting of pec-
are approximately 40,000 new cases diagnosed and 14,000 deaths. Male toralis major, in continuity laterally under serratus anterior with the
breast cancers constitute up to 1% of all mammary malignancies and intervening fascia, and the abdominal fascia inferiorly. The lower fibres
may include tissue beyond the areolar boundary. of the attachment of pectoralis major to the sixth rib need to be
Breast cancers arise within the epithelia of lobules or ducts. As they detached; otherwise, the implant will be placed too high on the chest
increase in size and infiltrate the stroma, they often lead to a fibrous wall. The tissue expander has to stretch the potential space below this
tissue reaction. Breast lumps may be classified as benign or malignant musculofascial plane to match the space created by the removed breast
masses. Malignant breast lumps may have the clinical signs of infiltrat- beneath the subcutaneous plane and the deep fascia overlying pectoralis
ing adjacent structures, leading to a hard and irregular mass with skin- major. The tissue expander is subsequently replaced by a silicone or
tethering, muscle fixation, skin infiltration or oedema of the overlying saline breast implant.
skin (peau d’orange). Standard radiological imaging investigations of the The skin and volume component of the breast can also be replaced
breast include mammography and ultrasonography. Mammography is by the latissimus dorsi musculocutaneous flap, with or without an
useful in detecting the presence of malignant masses as a stellate opacity underlying silicone or saline breast implant. Latissimus dorsi and an
with architectural distortion of the surrounding parenchyma. Early overlying paddle of skin are raised on its dominant vascular pedicle:
stages of preinvasive breast cancer, ductal cancer in situ, may appear as namely, the thoracodorsal vessels, which enter the muscle on its deep
microcalcification on the mammogram. An ultrasound scan of the surface and send perforating branches through the muscle to the overly-


breast is helpful to distinguish solid from cystic (or fluid-filled) masses, ing skin. The flap is transferred in an arc from the back to the front of
and can also aid in the distinction of breast cancer from benign lumps the chest and fashioned to make a new breast. An implant may be
by the different attenuation characteristics of the ultrasound waves and required to provide additional volume replacement, in which case it is
blood-flow patterns. Wrinkles caused by contraction of muscular fibres placed beneath the flap. The donor defect on the back is directly sutured.
in the areola described above may create critical angle shadowing in In selected cases, this flap can be raised with additional superficial fascia
breast ultrasound. and fat, to avoid the need for a silicone implant. This is known as the
Magnetic resonance imaging (MRI) is also useful in diagnosis, par- extended or autologous latissimus dorsi flap.
ticularly in women with younger, denser breasts, achieving higher sen- Women with a suitable abdominal panniculus may have breast
sitivity of breast cancer detection but with lower specificity. A cytological reconstruction utilizing this excess tissue. Historically, this was achieved
diagnosis of a breast lump can be achieved using fine needle aspiration with a pedicled transverse rectus abdominis musculocutaneous (TRAM)
(FNA) to evaluate the cellular component of a lump. FNA is also useful flap based on the superior epigastric artery, where the skin and fat of
to drain symptomatic breast cysts. A wide-bore needle biopsy is a pro- the lower abdomen, attached to the rectus muscle, are transposed into
cedure performed under local anaesthetic to obtain several pieces of the breast defect and shaped into a breast reconstruction.
specimen for a histological diagnosis with the tissue architecture main- The development of microvascular techniques over the last 30 years
tained. This permits distinction between in situ and invasive cancer, and has seen an increase in the popularity of free tissue transfers, based on
provides an indication of tumour subtype by evaluation of the patho- the deep inferior epigastric vessels, including muscle-sparing (MS-)
logical characteristics. Vacuum-assisted mammotome biopsies based on TRAM flaps and deep inferior epigastric artery perforator (DIEP) flaps.
the wide-bore needle enable some benign and indeterminate lesions to These flaps require dissection of the blood vessels within rectus


be excised for full histological analysis and, in some patients, can avoid abdominis, rather than sacrifice of the entire muscle, and this aims to
the need for conventional open surgery. reduce donor site morbidity, including hernias and bulging. Radiologi-
If a breast lump has to be surgically removed, the incision should cal investigations (CT angiograms, MRI and duplex) are used to deter-
be based, whenever possible, in the relaxed skin tension lines, for the mine the calibre and position of perforators within these flaps to
best cosmetic results. In women with sizeable malignant lesions in improve the accuracy of dissection and enhance surgical outcomes (Fig.
whom breast conservation surgery is to be attempted, the skin incision 53.26). Free TRAM and DIEP flap vessels are anastomosed to recipient
should be planned with consideration of the possible requirement for vessels in the chest; the internal thoracic or the thoracodorsal artery is
a subsequent mastectomy if the margins of excision are incompletely used most frequently for this purpose.
excised by pathological criteria (Swanson et al 2002). Most women with Breast reconstruction using an autologous method, such as the
single breast cancers of up to 4 cm in diameter are treated by breast extended latissimus dorsi, free MS-TRAM and DIEP flap, avoids the
conservation rather than mastectomy. This is a combination of surgery need for a silicone implant and has advantages in terms of producing
(tumour excision and sentinel node biopsy or clearance) together with a more natural appearance and achieving greater longevity of results.
external beam radiotherapy. Patients with larger tumours are treated by Free tissue transfers for breast reconstruction are also performed using
modified radical mastectomy with axillary lymph node clearance. buttock tissue (superior and inferior gluteal artery perforator flaps)
During axillary dissection to clear the axillary lymph nodes, the nerve and thigh tissue (transverse upper gracilis and anterolateral thigh flaps).
to serratus anterior, the thoracodorsal vessels, the nerve to latissimus
dorsi, and the medial and lateral pectoral nerves are all identified and
carefully preserved. The boundaries of the axillary dissection are the
nerve to serratus anterior medially, the thoracodorsal pedicle laterally


and the axillary vein superiorly. The posterior limit of the dissection is
the ventral surface of subscapularis. The superomedial limit of a level
1 axillary dissection extends to the lateral border of pectoralis minor at
the apex of the axilla; a level 2 dissection extends to the medial border
of pectoralis minor; and a level 3 dissection extends beyond the medial
border until it reaches the point where the axilla is limited by the first
rib (the latter is easily distinguished by its flat lateral surface, easily
palpable at surgery). Failure to preserve the nerve to serratus anterior
will result in winging of the scapula. The intercostobrachial nerve is
often sacrificed in an axillary lymph node clearance operation, and this
may result in anaesthesia of a narrow strip of sensation in the upper
medial border of the arm.
Reconstructive surgery for breast
cancer disease
Breast reconstruction may be performed at the time of mastectomy for
breast cancer, or at a later stage (Serletti and Moran 2000). During a
mastectomy where an immediate breast reconstruction is planned, the
glandular breast tissue is removed either through a conventional mas-
tectomy skin incision or in association with preservation of the native
breast skin, a form of mastectomy termed a skin-sparing mastectomy. Fig. 53.26 A CT angiogram showing the deep inferior epigastric artery
Patient selection is important to minimize risks of breast cancer recur- (red arrow) and a perforator (yellow arrow) emerging from the rectus
rence in the skin of the reconstructed breast mound or associated lymph sheath for MS-TRAM and DIEP flap reconstruction.


Chest wall and breast
949.e2
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Breast reconstruction using The first description of lower abdominal tissues being used as a free
autologous tissue flap appeared in 1979 (Holmstrom 1979), although at this time the
pedicled TRAM flap was a far more popular choice for reconstruction.
One of the earliest recorded breast reconstructions using latissimus
This was mainly because microvascular techniques were still in develop-
dorsi, based on the thoracodorsal pedicle, was published in 1906
ment and the required instruments and microscopes were not widely
(Tansini 1906). The flap incorporated superficial fascia and a skin
available. However, over the years, it became possible to achieve excel-
paddle attached to the muscle, and was used to replace part of the breast
lent, reliable results without the problems of fat necrosis and abdomi-
skin envelope that had been removed during the mastectomy. This form
nal wall weakness associated with the pedicled version (Schusterman
of breast reconstruction inexplicably fell out of regular use until the
1994, Grotting 1989, Arnez et al 1991). The TRAM flap particularly
1970s, when there was renewed interest in the latissimus dorsi musculo-
lends itself to microsurgical transfer on account of the characteristics of
cutaneous flap combined with silicone breast implants (Schneider et al
the supplying vessels (deep inferior epigastric artery is 2.5–3 mm in
1978, Bostwick 1977) and improved definitions of the vascular supply
diameter and its venae comitantes are 3 mm in diameter); the length
and territory of the flap (McCraw et al 1977, Maxwell et al 1979).
of the pedicle (frequently up to 15 cm); and the large surface area of
Later in the twentieth century, further developments of this most
skin supplied by these vessels (from the midline to a point lateral to
versatile flap meant that breast reconstruction could be performed
the anterior superior iliac spine below the level of the umbilicus).
without a silicone implant. The so-called ‘extended’ flap (Hokin and
Further developments in dissection techniques, combined with a
Silfverskiold 1987) used autologous tissues exclusively; it was designed