Download Costal Cartilages

Muhammad Sohaib Shahid
(Lecturer & Course Co-ordinator BS-MIT)
University Institute of Radiological
Sciences & Medical Imaging Technology
(UIRSMIT)
The Thoracic Wall
Structure of the Thoracic Wall
• The thoracic wall is covered on the outside by skin and by
muscles attaching the shoulder girdle to the trunk. It is
lined with parietal pleura.
• The thoracic wall is formed posteriorly by the thoracic
part of the vertebral column; anteriorly by the sternum
and costal cartilages ; laterally by the ribs and intercostal
spaces; superiorly by the suprapleural membrane; and
inferiorly by the diaphragm, which separates the thoracic
cavity from the abdominal cavity.
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Sternum
• The sternum lies in the midline of the anterior chest wall. It is a flat
bone that can be divided into three parts:
• Manubrium stern
• Body of the sternum
• Xiphoid process.
• The manubrium is the upper part of the sternum. It articulates with
the body of the sternum at the manubriosternal joint, and it also
articulates with the clavicles and with the first costal cartilage and
the upper part of the second costal cartilages on each side . It lies
opposite the third and fourth thoracic vertebrae.
• The body of the sternum articulates above with the manubrium at
the manubriosternal joint and below with the xiphoid process at
the xiphisternal joint. On each side it articulates with the second to
the seventh costal cartilages .
• The xiphoid process is a thin plate of cartilage that becomes
ossified at its proximal end during adult life. No ribs or costal
cartilages are attached to it.
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• The sternal angle (angle of Louis), formed by the articulation
of the manubrium with the body of the sternum, can be
recognized by the presence of a transverse ridge on the
anterior aspect of the sternum . The transverse ridge lies at
the level of the second costal cartilage, the point from which
all costal cartilages and ribs are counted. The sternal angle lies
opposite the intervertebral disc between the fourth and fifth
thoracic vertebrae.
• The xiphisternal joint lies opposite the body of the ninth
thoracic vertebra
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Clinical Notes
Sternum and Marrow Biopsy
• Since
the
sternum
possesses
red
hematopoietic marrow throughout life, it is a
common site for marrow biopsy. Under a local
anaesthetic, a wide-bore needle is introduced
into the marrow cavity through the anterior
surface of the bone.
• The sternum may also be split at operation to
allow the surgeon to gain easy access to the
heart, great vessels, and thymus.
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Ribs
• There are 12 pairs of ribs, all of which are
attached posteriorly to the thoracic vertebrae .
The ribs are divided into three categories:
• True ribs: The upper seven pairs are attached
anteriorly to the sternum by their costal
cartilages.
• False ribs: The 8th, 9th, and 10th pairs of ribs are
attached anteriorly to each other and to the 7th
rib by means of their costal cartilages and small
synovial joints.
• Floating ribs: The 11th and 12th pairs have no
anterior attachment.
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Typical Rib
• A typical rib is a long, twisted, flat bone having a rounded,
smooth superior border and a sharp, thin inferior border . The
inferior border overhangs and forms the costal groove, which
accommodates the intercostal vessels and nerve. The anterior
end of each rib is attached to the corresponding costal cartilage .
• A rib has a head, neck, tubercle, shaft, and angle . The head has
two facets for articulation with the numerically corresponding
vertebral body and that of the vertebra immediately above . The
neck is a constricted portion situated between the head and the
tubercle. The tubercle is a prominence on the outer surface of
the rib at the junction of the neck with the shaft. It has a facet
for articulation with the transverse process of the numerically
corresponding vertebra (Fig. 2-4). The shaft is thin and flattened
and twisted on its long axis. Its inferior border has the costal
groove. The angle is where the shaft of the rib bends sharply
forward.
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Atypical Rib
• The first rib is important clinically because of its close
relationship to the lower nerves of the brachial plexus
and the main vessels to the arm, namely, the subclavian
artery and vein .
• This rib is small and flattened from above downward. The
scalenus anterior muscle is attached to its upper surface
and inner border. Anterior to the scalenus anterior, the
subclavian vein crosses the rib; posterior to the muscle
attachment, the subclavian artery and the lower trunk of
the brachial plexus cross the rib and lie in contact with
the bone.
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Clinical Notes
Cervical Rib
• A cervical rib (i.e., a rib arising from the anterior
tubercle of the transverse process of the seventh
cervical vertebra) occurs in about 0.5% of humans . It
may have a free anterior end, may be connected to the
first rib by a fibrous band, or may articulate with the
first rib.
• The importance of a cervical rib is that it can cause
pressure on the lower trunk of the brachial plexus in
some patients, producing pain down the medial side of
the forearm and hand and wasting of the small muscles
of the hand. It can also exert pressure on the overlying
subclavian artery and interfere with the circulation of
the upper limb.
.
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Rib Excision
• Rib excision is commonly performed by
thoracic surgeons wishing to gain entrance to
the thoracic cavity. A longitudinal incision is
made through the periosteum on the outer
surface of the rib and a segment of the rib is
removed. A second longitudinal incision is
then made through the bed of the rib, which
is the inner covering of periosteum. After the
operation, the rib regenerates from the
osteogenetic layer of the periosteum.
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Rib Fractures
• Fractures of the ribs are common chest injuries.
• In children, the ribs are highly elastic, and fractures in this age
group are therefore rare. Unfortunately, the pliable chest wall in
the young can be easily compressed so that the underlying lungs
and heart may be injured.
• With increasing age, the rib cage becomes more rigid, owing to
the deposit of calcium in the costal cartilages, and the ribs become
brittle. The ribs then tend to break at their weakest part, their
angles.
• The ribs prone to fracture are those that are exposed or relatively
fixed. Ribs 5 through 10 are the most commonly fractured ribs.
The first four ribs are protected by the clavicle and pectoral
muscles anteriorly and by the scapula and its associated muscles
posteriorly.
• Because the rib is sandwiched between the skin externally and the
delicate pleura internally, it is not surprising that the jagged ends
of a fractured rib may penetrate the lungs and present as a
pneumothorax.
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Rib Contusion
• Bruising of a rib, secondary to trauma, is the most
common rib injury. In this painful condition, a small
haemorrhage occurs beneath the periosteum.
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Costal Cartilages
• Costal cartilages are bars of cartilage connecting
the upper seven ribs to the lateral edge of the
sternum and the 8th, 9th, and 10th ribs to the
cartilage immediately above. The cartilages of the
11th and 12th ribs end in the abdominal
musculature .
• The costal cartilages contribute significantly to
the elasticity and mobility of the thoracic walls. In
old age, the costal cartilages tend to lose some of
their flexibility as the result of superficial
calcification.
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Joints of the Chest Wall
• Joints of the Sternum
• The manubriosternal joint is a cartilaginous joint between the
manubrium and the body of the sternum. A small amount of
angular movement is possible during respiration. The xiphisternal
joint is a cartilaginous joint between the xiphoid process (cartilage)
and the body of the sternum. The xiphoid process usually fuses
with the body of the sternum during middle age.
Joints of the Ribs
• Joints of the Heads of the Ribs
• The first rib and the three lowest ribs have a single synovial joint
with their corresponding vertebral body. For the second to the
ninth ribs, the head articulates by means of a synovial joint with the
corresponding vertebral body and that of the vertebra above it .
There is a strong intraarticular ligament that connects the head to
the intervertebral disc
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Joints of the Tubercles of the Ribs
• The tubercle of a rib articulates by means of a synovial joint
with the transverse process of the corresponding vertebra .
(This joint is absent on the 11th and 12th ribs.)
Joints of the Ribs and Costal Cartilages
• These joints are cartilaginous joints. No movement is
possible.
Joints of the Costal Cartilages with the Sternum
• The first costal cartilages articulate with the manubrium, by
cartilaginous joints that permit no movement . The 2nd to
the 7th costal cartilages articulate with the lateral border of
the sternum by synovial joints. In addition, the 6th, 7th, 8th,
9th, and 10th costal cartilages articulate with one another
along their borders by small synovial joints. The cartilages of
the 11th and 12th ribs are embedded in the abdominal
musculature.
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Movements of the Ribs and Costal Cartilages
• The 1st ribs and their costal cartilages are fixed to the
manubrium and are immobile. The raising and
lowering of the ribs during respiration are
accompanied by movements in both the joints of the
head and the tubercle, permitting the neck of each
rib to rotate around its own axis.
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Thoracic Outlet
• The chest cavity communicates with the root of the neck through
an opening called the thoracic outlet. It is called an outlet
because important vessels and nerves emerge from the thorax
here to enter the neck and upper limbs.
•
The opening is bounded posteriorly by the first thoracic vertebra,
laterally by the medial borders of the first ribs and their costal
cartilages, and anteriorly by the superior border of the
manubrium sterni. The opening is obliquely placed facing upward
and forward. Through this small opening pass the oesophagus and
trachea and many vessels and nerves. Because of the obliquity of
the opening, the apices of the lung and pleurae project upward
into the neck.
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• The thoracic cavity communicates with the abdomen
through a large opening. The opening is bounded
posteriorly by the 12th thoracic vertebra, laterally by
the curving costal margin, and anteriorly by the
xiphisternal joint. Through this large opening, which
is closed by the diaphragm, pass the oesophagus and
many large vessels and nerves, all of which pierce the
diaphragm.
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Clinical Notes
• The Thoracic Outlet Syndrome
• The brachial plexus of nerves (C5, 6, 7, and 8 and
T1) and the subclavian artery and vein are closely
related to the upper surface of the first rib and
the clavicle as they enter the upper limb . It is
here that the nerves or blood vessels may be
compressed between the bones. Most of the
symptoms are caused by pressure on the lower
trunk of the plexus producing pain down the
medial side of the forearm and hand and wasting
of the small muscles of the hand. Pressure on the
blood vessels may compromise the circulation of
the upper limb.
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Intercostal Spaces
• The spaces between the ribs contain three muscles of
respiration:
• The external intercostal
• The internal intercostal
• The innermost intercostal muscle.
The innermost intercostal muscle is lined internally by
the endothoracic fascia, which is lined internally by the
parietal pleura. The intercostal nerves and blood
vessels run between the intermediate and deepest
layers of muscles . They are arranged in the following
order from above downward: intercostal vein,
intercostal artery, and intercostal nerve (i.e., VAN).
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Intercostal Muscles
• The external intercostal muscle forms the
most superficial layer. Its fibers are directed
downward and forward from the inferior
border of the rib above to the superior border
of the rib below . The muscle extends forward
to the costal cartilage where it is replaced by
an aponeurosis, the anterior (external)
intercostal membrane .
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• The internal intercostal muscle forms the
intermediate layer. Its fibers are directed
downward and backward from the subcostal
groove of the rib above to the upper border of
the rib below . The muscle extends backward
from the sternum in front to the angles of the
ribs behind, where the muscle is replaced by
an aponeurosis, the posterior (internal)
intercostal membrane
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• The innermost intercostal muscle forms the
deepest layer and corresponds to the
transversus abdominis muscle in the anterior
abdominal wall. It is an incomplete muscle
layer and crosses more than one intercostal
space within the ribs. It is related internally to
fascia (endothoracic fascia) and parietal pleura
and externally to the intercostal nerves and
vessels. The innermost intercostal muscle can
be divided into three portions , which are
more or less separate from one another.
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Action
• When the intercostal muscles contract, they all tend to
pull the ribs nearer to one another. If the 1st rib is fixed
by the contraction of the muscles in the root of the
neck, namely, the scaleni muscles, the intercostal
muscles raise the 2nd to the 12th ribs toward the first
rib, as in inspiration. If, conversely, the 12th rib is fixed
by the quadratus lumborum muscle and the oblique
muscles of the abdomen, the 1st to the 11th ribs will
be lowered by the contraction of the intercostal
muscles, as in expiration.
• In addition, the tone of the intercostal muscles during
the different phases of respiration serves to strengthen
the tissues of the intercostal spaces, thus preventing
the sucking in or the blowing out of the tissues with
changes in intrathoracic pressure.
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Nerve Supply
• The intercostal muscles are supplied by the
corresponding intercostal nerves.
• The intercostal nerves and blood vessels (the
neurovascular bundle), as in the abdominal wall,
run between the middle and innermost layers of
muscles . They are arranged in the following
order from above downward: intercostal vein,
intercostal artery, and intercostal nerve (i.e.,
VAN).
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Suprapleural Membrane
• Superiorly, the thorax opens into the root of the neck by a
narrow aperture, the thoracic outlet . The outlet transmits
structures that pass between the thorax and the neck
(oesophagus, trachea, blood vessels, etc.) and for the
most part lie close to the midline.
• On either side of these structures the outlet is closed by a
dense fascial layer called the suprapleural membrane .
• This tent-shaped fibrous sheet is attached laterally to the
medial border of the first rib and costal cartilage. It is
attached at its apex to the tip of the transverse process of
the seventh cervical vertebra and medially to the fascia
investing the structures passing from the thorax into the
neck.
• It protects the underlying cervical pleura and resists the
changes in intrathoracic pressure occurring during
respiratory movements.
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Diaphragm
• The diaphragm is a thin muscular and tendinous septum that
separates the chest cavity above from the abdominal cavity
below . It is pierced by the structures that pass between the
chest and the abdomen.
• The diaphragm is the most important muscle of respiration. It
is dome shaped and consists of a peripheral muscular part,
which arises from the margins of the thoracic opening, and a
centrally placed tendon .
The origin of the diaphragm can be divided into three parts:
• A sternal part arising from the posterior surface of the
xiphoid process .
• A costal part arising from the deep surfaces of the lower six
ribs and their costal cartilages .
• A vertebral part arising by vertical columns or crura and
from the arcuate ligaments
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• The right crus arises from the sides of the bodies of the
first three lumbar vertebrae and the intervertebral discs.
• The left crus arises from the sides of the bodies of the
first two lumbar vertebrae and the intervertebral disc .
Lateral to the crura the diaphragm arises from the
medial and lateral arcuate ligaments .
• The medial arcuate ligament extends from the side of
the body of the second lumbar vertebra to the tip of the
transverse process of the first lumbar vertebra.
• The lateral arcuate ligament extends from the tip of
the transverse process of the first lumbar vertebra to the
lower border of the 12th rib.
• The medial borders of the two crura are connected by a
median arcuate ligament, which crosses over the
anterior surface of the aorta
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• The diaphragm is inserted into a central tendon,
which is shaped like three leaves.
• The superior surface of the tendon is partially fused
with the inferior surface of the fibrous pericardium.
• Some of the muscle fibers of the right crus pass up to
the left and surround the esophageal orifice in a sling
like loop. These fibers appear to act as a sphincter
and possibly assist in the prevention of regurgitation
of the stomach contents into the thoracic part of the
oesophagus
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Shape of the Diaphragm
• As seen from in front, the diaphragm curves up into right and left
domes, or cupulae. The right dome reaches as high as the upper
border of the fifth rib, and the left dome may reach the lower
border of the fifth rib.
• (The right dome lies at a higher level, because of the large size of
the right lobe of the liver.)
• The central tendon lies at the level of the xiphisternal joint. The
domes support the right and left lungs, whereas the central tendon
supports the heart.
• The levels of the diaphragm vary with the phase of respiration,
the posture, and the degree of distention of the abdominal viscera.
The diaphragm is lower when a person is sitting or standing; it is
higher in the supine position and after a large meal.
• When seen from the side, the diaphragm has the appearance of an
inverted J, the long limb extending up from the vertebral column
and the short limb extending forward to the xiphoid process
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Openings in the Diaphragm
• The diaphragm has three main openings:
• The aortic opening lies anterior to the body of the 12th
thoracic vertebra between the crura . It transmits the
aorta, the thoracic duct, and the azygos vein.
• The esophageal opening lies at the level of the 10th
thoracic vertebra in a sling of muscle fibers derived
from the right crus . It transmits the oesophagus, the
right and left vagus nerves, the esophageal branches of
the left gastric vessels, and the lymphatics from the
lower third of the oesophagus.
• The caval opening lies at the level of the eighth 8th
thoracic vertebra in the central tendon . It transmits the
inferior vena cava and terminal branches of the right
phrenic nerve.
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Functions of the Diaphragm
• Muscle of inspiration: On contraction, the diaphragm pulls its central
tendon down and increases the vertical diameter of the thorax. The
diaphragm is the most important muscle used in inspiration.
• Muscle of abdominal straining: The contraction of the diaphragm assists
the contraction of the muscles of the anterior abdominal wall in raising the
intra-abdominal pressure for micturition, defecation, and parturition. This
mechanism is further aided by the person taking a deep breath and closing
the glottis of the larynx. The diaphragm is unable to rise because of the air
trapped in the respiratory tract. Now and again, air is allowed to escape,
producing a grunting sound.
• Weight-lifting muscle: In a person taking a deep breath and holding it
(fixing the diaphragm), the diaphragm assists the muscles of the anterior
abdominal wall in raising the intra-abdominal pressure to such an extent
that it helps support the vertebral column and prevent flexion. This greatly
assists the postvertebral muscles in the lifting of heavy weights. Needless
to say, it is important to have adequate sphincteric control of the bladder
and anal canal under these circumstances.
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• Thoracoabdominal pump: The descent of the
diaphragm decreases the intrathoracic pressure and at
the same time increases the intra-abdominal pressure.
This pressure change compresses the blood in the
inferior vena cava and forces it upward into the right
atrium of the heart. Lymph within the abdominal
lymph vessels is also compressed, and its passage
upward within the thoracic duct is aided by the
negative intrathoracic pressure. The presence of
valves within the thoracic duct prevents backflow.
Action of the Diaphragm
• On contraction, the diaphragm pulls down its central
tendon and increases the vertical diameter of the
thorax.
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Nerve Supply of the Diaphragm
• Motor nerve supply: The right and left phrenic
nerves (C3, 4, 5)
• Sensory nerve supply: The parietal pleura and
peritoneum covering the central surfaces of the
diaphragm are from the phrenic nerve and the
periphery of the diaphragm is from the lower six
intercostal nerves.
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Paralysis of the Diaphragm
• A single dome of the diaphragm may be paralyzed by
crushing or sectioning of the phrenic nerve in the neck.
• This may be necessary in the treatment of certain forms
of lung tuberculosis, when the physician wishes to rest
the lower lobe of the lung on one side.
• Occasionally, the contribution from the fifth cervical
spinal nerve joins the phrenic nerve late as a branch from
the nerve to the subclavius muscle. This is known as the
accessory phrenic nerve. To obtain complete paralysis
under these circumstances, the nerve to the subclavius
muscle must also be sectioned.
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Hiccup
• Hiccup is the involuntary spasmodic contraction of the
diaphragm accompanied by the approximation of the vocal
folds and closure of the glottis of the larynx.
• It is a common condition in normal individuals and occurs
after eating or drinking as a result of gastric irritation of the
vagus nerve endings.
• It may, however, be a symptom of disease such as pleurisy,
peritonitis, pericarditis, or uraemia.
Thoracotomy
• In patients with penetrating chest wounds with uncontrolled
intrathoracic haemorrhage, thoracotomy may be a life-saving
procedure
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Internal Thoracic Artery
• The internal thoracic artery supplies the anterior wall of the body from the
clavicle to the umbilicus. It is a branch of the first part of the subclavian
artery in the neck. It descends vertically on the pleura behind the costal
cartilages, a fingerbreadth lateral to the sternum, and ends in the sixth
intercostal space by dividing into the superior epigastric and musculophrenic
arteries .
• Branches
• Two anterior intercostal arteries for the upper six intercostal spaces
• Perforating arteries, which accompany the terminal branches of the
corresponding intercostal nerves
• The pericardiacophrenic artery, which accompanies the phrenic nerve and
supplies the pericardium
• Mediastinal arteries to the contents of the anterior mediastinum (e.g., the
thymus)
• The superior epigastric artery, which enters the rectus sheath of the
anterior abdominal wall and supplies the rectus muscle as far as the
umbilicus
• The musculophrenic artery, which runs around the costal margin of the
diaphragm and supplies the lower intercostal spaces and the diaphragm
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•
•
•
•
Internal Thoracic Vein
The internal thoracic vein accompanies the internal
thoracic artery and drains into the brachiocephalic
vein on each side.
Levatores Costarum
There are 12 pairs of muscles. Each levator costa is
triangular in shape and arises by its apex from the tip
of the transverse process and is inserted into the rib
below.
Action: Each raises the rib below and is therefore an
inspiratory muscle.
Nerve supply: Posterior rami of thoracic spinal
nerves
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• Serratus Posterior Superior Muscle
• The serratus posterior superior is a thin, flat muscle that
arises from the lower cervical and upper thoracic
spines. Its fibers pass downward and laterally and are
inserted into the upper ribs.
• Action: It elevates the ribs and is therefore an
inspiratory muscle.
• Nerve supply: Intercostal nerves
• Serratus Posterior Inferior Muscle
• The serratus posterior inferior is a thin, flat muscle that
arises from the upper lumbar and lower thoracic spines.
Its fibers pass upward and laterally and are inserted into
the lower ribs.
• Action: It depresses the ribs and is therefore an
expiratory muscle.
• Nerve supply: Intercostal nerves
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Internal Thoracic Artery in the
Treatment of Coronary Artery Disease
• In patients with occlusive coronary disease
caused by atherosclerosis, the diseased arterial
segment can be bypassed by inserting a graft.
The graft most commonly used is the great
saphenous vein of the leg .
• In some patients, the myocardium can be
revascularize by surgically mobilizing one of
the internal thoracic arteries and joining its
distal cut end to a coronary artery.
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Radiographic Anatomy of Chest
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