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THE THORACIC WALL
OPERATIONS ON THE THORACIC WALL
The superior border of the thorax is drawn from the suprasÂternal notch, along the
clavicle to acromioclavicular joint and further passes along the line, which is drawn from
the spinal process of C7.
The inferior border of the thorax is drawn from the xiphoid process, along the
margin of the costal arch to the tenth rib and further passes through the tips (ends) of XIXII ribs to the spinous process of the XII thoracic vertebra.
The thoracic wall is supported by the thoracic cage. The thoracic cage is formed by
the vertebral column behind, the ribs and intercostal space on both side and the sternum
and costal cartilages in front.
Superiorly the thorax communicates with the neck through the thoracic inlet and
inferiorly it is separated from the abdoÂmen by the diaphragm. The dimension of the
thoracic cavity is smaller that the dimension of the thoracic wall, as the diaphÂragm is
located higher that the inferior border of the thorax. The thoracic cage protects the lungs
and the heart and affords attachment for the muscles of the thorax, upper extremities, abÂdomen and back.
Surface landmarks of the thorax are: clavicles, sternum, ribs and costal arches,
suprasternal notch, sternal angle, subÂcostal angle (this is situated at the inferior end of the
sterÂnum, between the sternal attachments of the seventh costal carÂtilages), spinous
processes of thoracic vertebra, scapula (spine of the scapula, inferior angle), nipple (in the
male it usually lies in the fourth intercostal space; in the female its position is not constant).
Apex beat of the heart is normally found in the fifth left intercostal space 1.5- 2 cm medially
from the midclavicular line.
Lines of orientation are drown for determination of the projection of the lungs, heart
and the organs of the abdominal cavity. They are midsternal line, sternal line,
peri(para)sterÂnal line, midclavicular line, anterior axillary line, midaxillaÂry line,
posterior axillary line, scapular line, posterior midÂline, vertebral line, paravertebral line.
THE LAYERS OF THE THORACIC CAGE.
1)Skin;
2)Subcutaneous tissue. This layer contains the superficial veins, which form
anastomosises. The main vein is the thoracoepiÂgastric vein. The skin is supplied by
the supraclavicular nerves and anterior branches of the intercostal nerves;
3)Superficial fascia. It forms the capsule (sheath) of the mammary gland;
4)Proper fascia. It covers the superficial group of muscles;
5)The superficial group of muscles covers 6)the thoracic cage and the intercostal
muscles between adjacent ribs. Pectoralis major muscle, pectoralis minor, subclavius
muscle cover the thoÂrax anteriorly; serratus anterior muscle covers the thorax lateÂrally,
latissimus dorsi muscle covers the thorax posteriorly and partially laterally; external
oblique muscle covers the thorax inferiorly and laterally.
7)The internal surface of the thoracic wall is lined by the endothoracic fascia.
9)Parietal pleura also covers the inner surface of the chest wall deeply to the
endothoracic fascia. 8)The thin layer of the fat is located between endothoracic fascia and
parietal pleura. A needle passed through the thoracic wall to enter the pleural cavity must
transverse each of these soft tissue layers.
The lymph drainage of the skin, of the anterior chest wall passed to the anterior
axillary lymph nodes; that from the posÂterior chest wall passed to the posterior axillary
nodes. Near the midline, anteriorly, lymphatic vessels pierce the anterior ends of the
intercostal spaces to reach the parasternal nodes which lie along the internal thoracic
artery and vein.
The breasts or mammary glands.
The base of the glands extends
from the second-third rib – superiorly
to the seventh rib – inferiorly and
from the sternal line – medially
to the anterior axillary line – laterally.
The gland lies in the superficial fascia and on the deep fascia coÂvering the
pectoralis major and serratus anterior muscle. It is composed of fifteen to twenty lobes
containing a duct system, lobules of glandular tissue, supporting connective tissue and
surrounding fat. The lobes radiate out from the nipple. A single lactiferous duct from each
lobe opens onto the nipple. These ducts become expanded deep to the nipple to form
lactiferous siÂnuses.
The base of the nipple is surrounded by the areola. The loÂbes of the gland are
separated by fibrous septa, which are forÂmed by superficial fascia. Superficial fascia is
attached to clavicle and forms suspensory ligament of Cooper.
The mammary glands are separated from the deep fascia covering the underlying
muscles by an area of loose connective tissue known as the retromammary space. This
space provides the mobility of the mamÂmary gland in norm. In advanced carcinoma of
the breasts the tuÂmor may invade the underlying pectoralis major muscle and its fascia.
Understand, that this condition leads to the fixation of the malignant breast lesion to the
chest wall.
Cancer of the breast and its accompanying fibrosis also has a tendency to shorten
the suspensory ligaments of Cooper. UnÂderstand, that the resulting traction of Cooper's
ligaments on the skin leads to a characteristic dimpling of the skin.
The upper lateral edge of the mammary gland extends around the lower border of
the pectoralis major and enters the axilla. It is the so-called axillary tail. It pierces the deep
fascia at the lower border of the pectoralis major muscle.
The arterial supply of the mammary gland is from perforating branches of the
internal thoracic artery and the intercosÂtal arteries. The axillary artery also supplies the
gland via its lateral thoracic and thoracoacromial branches. The veins correspond the
arteries. Cells from malignant tumors of the breÂast may gain entry to these veins and
account for widespread seÂcondary tumors.
The lymphatic drainage of the breast assumes great importance in the treatment of
malignant tumors and the assessment of their prognosis for it is along lymphatic channels
that disÂsemination most commonly occurs. Lymph from the gland drain into a deep
submammary or a superficial subareolar plexus. FurtÂher lymphatic channels radiate from
these plexuses laterally – to axillary nodes (pectoral, central, apical), upward – to
infraclaÂvicular and supraclavicular nodes, medially – to the contralateÂral breast and
nodes along the internal thoracic artery (parasternal) and henÂce to mediastinal nodes;
inferiorly- to the extraperitoneal tisÂsues.
For practical purposes the breast is divided into quadrants when considering the
lymph drainage. They are superior and infeÂrior lateral quadrants and superior and inferior
medial quadÂrants.
1)The lateral quadrants of the breast drains into the anteÂrior axillary or pectoral
nodes.
2)The medial quadrants of the breast is drained by means vessels, that pierce the
intercostal spaces and enter nodes lyÂing along the internal thoracic artery within the
thorax.
3)The inferior medial quadrant can drain into the extrapeÂritoneal tissues and hence
to nodes of the of the organs of the supracolic compartment or superior storey (floor) of
the abdomiÂnal cavity.
4)Some vessels from medial quadrants communicate with the lymph vessels of the
opposite breast.
5)Some lymph vessels pass through pectoralis major muscle and pectoralis
minor muscle to nodes lying under pectoralis miÂnor muscle.
6)The superior medial and lateral quadrants of the breast can drain into
infraclavicular and supraclavicular nodes.
The main nodes are axillary nodes and nodes Sorgius. Nodes Sorgius lie on the third
rib under the margin of the pectoralis major muscle. The tumors arising in the lateral half
of the breÂast more that 60% will involve the axillary nodes.
The intercostal spaces.
The intercostal spaces lie between the ribs. They are larÂgely filled by the external
and internal intercostal muscles. However, deep to each external intercostal muscle and
under coÂver of the costal groove lies a neurovascular bundle made up by intercostal vein,
artery and nerve, arranged in that order from above downward.
The intercostal muscles.
The fibers of the external intercostal muscles run downward and forward from the
lower border of the rib above to the upper border of the rib below. The muscle is deficient
anteriorly beÂing replaced by a fibrous membrane, the external intercostal membrane.
Fibers of the internal intercostal muscles run downward and backward deep to the
external muscles. The fibers of this muscle are deficient posteriorly and replaced by the
internal intercosÂtal membrane.
The transversus thoracis muscle forms a discontinuous layer on the deep surface of
the thoracic cage linking ribs to ribs and costal cartilages to sternum. It is related internally
to endothoracic fascia and parietal pleura.
The nerve supply of all these muscles is from the adjacent intercostal nerves. The
action of the intercostal muscles are concerned with respiration.
The vessels and nerve pass into intercostal canal. It is formed by external
intercostal muscle - externally,Â
by internal intercostal muscleÂ
 internally and by  costal  groove - superiorly.
The intercostal and subcostal nerves lie below the intercostal vessels. ...
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