INTRODUCT!ON
Superior vena cava brings deoxygenated blood from
the head and neck, upper limbs and thorax to the heart.
Aorta and pulmonary trunk are the only two exit
channels from the heart, developing from a single
truncus arteriosus. The two are intimately related to
each other.
LARGE BLOOD WESSELS
DISSECIION
Trace superior vena cava from level of first right costal
cartilage where it is formed by union of left and right
brachiocephalic veins tillthe third costal cartilage where
it opens into right atrium.
Trace the ascending aorta from the vestibule of left
ventricle upwards between superior vena cava and
pulmonary trunk.
Arch of aorta is seen above the bifurcation of
pulmonary trunk.
Cut ligamentum aderiosum as it connects the left
pulmonary artery to the arch of aofta.
Trace the left recurrent laryngeal nerve to the medial
aspect of arch of aofta.
Lift the side of oesophagus foruvards to expose the
anterior surface of the descending aofta.
Lift the diaphragm fonrvards and expose the aofia in
the inferior part of the posterior mediastinum.
SUPERIOR VENA C
Superior vena cava is a large venous channel which
collects blood from the upper half of the body and
drains it into the right atrium. It is formed by the union
of the right and left brachiocephalic or innominate veins
behind the lower border of the first right costal cartilage
close to the sternum. Each brachiocephalic vein is
formed behind the corresponding sternoclavicular joint
by the union of the internal jugular and subclavian veins
(Fig. 1e.1).
Coulse
The superior vena cava is about 7 cm long. It begins
behind the lower border of the sternal end of the first
right costal cartilage, pierces the pericardium opposite
the second right costal cartilage, and terminates by
opening into the upper part of the right atrium behind
the third right costal cartilage (Fig.79.2).It has no
valves.
Relotions
L Anterior
a. Chest wall.
b. Internal thoracic vessels.
c. Anterior margin of the right lung and pleura.
d. The vessel is covered by pericardium in its lower
half (Fig. 1e.2).
2 Posterior
a. Trachea and right vagus (posteromedial to the
upper part of the vena cava) (see Fig.16.2).
b. Root of right lung posterior to the lower part.
3 Medinl
a. Ascending aorta.
b. Brachiocephalic artery.
4 Laternl
a. Right phrenic nerve with accompanying vessels.
b. Right pleura and lung (Fig. 19.3).
Tribuloiles
1 The azygosvein arches over the root of the right lung
and opens into the superior vena cava at the level of
the second costal cartilage, just before the latter enters
the pericardium.
2 Several small mediastinal and pericardial veins drain
into the vena cava.
CLINICAL ANATOMY
When the superior vena cava is obstructed above
the opening of the azygos vein, the venous blood
of the upper half of the body is returned through
the azygos vein; and the superficial veins are
dilated on the chest up to the costal margin
(Fig. 19.a). Blood from upper limb is returned
through the communicating veins joining the
veins around the scapula with the intercostal
veins. The latter veins of both sides drain into vena
azySos.
When the supericlr vena cava is obstructed below
the opening of the azygos veins, the blood is
returned through the inferior vena cava via the
femoral vein; and the superior veins are dilated
on both the chest and abdomen up to the
saphenous opening in the thigh. The superficial
vein connecting the lateral thoracic vein with the
superficial epigastric vein is known as the
thoracoepigastric v ein (Fig. 19.5).
o In cases of mediastinal syndrome, the signs of
superior vena caval obstruction are the first to
aPPear.
AORTA
The aorta is the great arterial trunk which receives
oxygenated blood from the left ventricle and distributes
it to all parts of the body. It is studied in thorax in the
following three parts:
1 Ascending aorta.
2 Arch of the aorta.
3 Descending thoracic aorta.
ASCENDING AORTA
Origin ond Course
The ascending aorta arises from the upper end of the
left ventricle. It is about 5 cm long and is enclosed in
the pericardium (Fig. 19.2).
It begins behind the left half of the stemum at the
level of the lower border of the third costal cartilage.
It runs upwards, forwards and to the right and becomes
continuous with the arch of the aorta at the sternal
end of the upper border of the second right costal
cartilage.
At the root of the aorta there are three dilatations of
the vessel wall called the aortic sinuses. The sinuses are
anterior, left posterior and right posterior.
Relolions
,4*d***:r
1 Sternum.
2 Right lung and pleura.
3 Infundibulum of the right ventricle.
4 Root of the pulmonary trunk (Fig. 19.3).
5 Right auricle.
,s{:sf#ru’#r
Transverse sinus of pericardium.
Left atrium.
Right pulmonary artery.
Right bronchus (Fig. 19.3).
f’r* ffte d
1 Superior vena cava.
2 Right atrium.
i* ff+e f,*f$
1 Pulmonary trunk above.
2 LeIt atrium below.
Bronches
L The right coronary artery arises from anterior aortic
sinus (see Fig. 78.22a).
2 Left coronary artery arises from the left posterior
aortic sinus.
CLINICAL ANATOMY
Aortic knuckle: In posteroanterior view of
radiographs of the chest, the arch of the aorta is
seen as a projection beyond the left margin of the
mediastinal shadow. The projection is called the
aortic knuckle. It becomes prominent in old age
(see Fig.21..12).
Coarctation of the aorta is a localised narrowing of
the aorta opposite to or justbeyond the attachment
of the ductus arteriosus. An extensive collateral
circulation develops between the branches of the
subclavian arteries and those of the descending
aorta. These include the anastomoses between the
anterior and posterior intercostal arteries. These
arteries enlarge greatly and produce a
characteristic notching on the ribs (Fig. 19.6).
D uctus ar t er io sus, lig nmentum ar t er io sum and p at ent
ductus arteriosus: During foetal life, the ductus
arteriosus is a short wide channel connecting the
beginning of the left pulmonary artery with the
arch of the aorta immediately distal to the origin
of the left subclavian artery. It conducts most of
the blood from the right ventricle into the aorta,
thus short circuiting the lungs. After birth it is
closed functionally within about a week and
anatomically within about eight weeks. The
remnants of the ductus form a fibrous band called
tli.e ligamentum arteriosum (Fig. 19.7). The left
recurrent laryngeal nerve hooks around the
ligamentum arteriosum.
The ductus may remain patent after birth. The
condition is calledpatent ductus arteriosus and may
cause serious problems. The condition can be
surgically treated.
. Aortic arch aneurysz is a localised dilatation of the
aorta which may press upon the left recurrent
laryngeal nerve ieiaing to paralysis of left vocal
cord and hoarseness. It may also press upon the
surrounding structures and cause the mediastinal
syndrome (Fig. 19.8), i.e. dyspnoea, dysphagia,
dysphonia, etc.
ARCH OF THE AORTA
Arch of the aorta is the continuation of the ascending
aorta. It is situated in the superior mediastinumbehind
the lower half of the manubrium sterni.
Course
1 It begins behind the upper border of the second right
sternochondral joint (see Figs 17.2 to 17.4).
2 It runs upwards, backwards and to the left across
the left side of the bifurcation of trachea. Then it
passes downwards behind the left bronchus and on
the left side of the body of the fourth thoracic
vertebra. It thus arches over the root of the left lung.
3 It ends at the lower border of the body of the fourth
thoracic vertebra by becoming continuous with the
descending aorta.
Thus the beginning and the end of arch of aorta are
at the same level although it begins anteriorly and
ends posteriorly.
Relotions
4*fe**rJp, *?f,td f# ffrpe d*ffl
1 Four nerves from before backwards:
a. Left phrenic.
b. Lower cervical cardiac branch of the left vagus.
c. Superior cervical cardiac branch of left
sympathetic chain.
d. Left vagus (Fig. 19.9).
2 Left superior intercostal vein, deep to the phrenic
nerve and superficial to the vagus nerve.
3 Left pleura and lung.
4 Remains of thymus.
Fosferiorfy smd f# ifr# f
I Trachea, with the deep cardiac plexus and the
tracheobronchial lymph nodes.
2 Oesophagus. ,,
3 Left recurrent laryngeal nerve.
4 Thoracic duct.
5 Vertebral column.
Suf*emor
1 Three branches of the arch of the aorta:
a. Brachiocephalic.
b. Left common carotid.
c. Left subclavian arterles (Fig. 19.10).
2 All three arteries are crossed close to their origin by
the left brachiocephalic vein.
rFr:feni*r
1 Bifurcation of the pulmonary trunk.
2 Left bronchus.
3 Ligamentum arteriosum with superficial cardiac
plexus on it.
4 Left recurrent laryngeal nerve.
Bronches
1 Brachiocephalic artery which divides into the right
common carotid and right subclavian arteries
(Fig.7e.2).
2 Left common carotid artery.
3 Left subclavian artery.
DESCENDINE IHO CIC AORTA
Descending thoracic aorta is the continuation of the arch
of the aorta. It lies in the posterior mediastinum
(see Fig.77.4).
Course
1 It begins on the left side of the lower border of the
body of the fourth thoracic vertebra.
2 It descends with an inclination to the right and
terminates at the lower border of the twelfth thoracic
vertebra.
Relolions
,4rnf*’rier
1 Root of left lung.
2 Pericardium and heart.
3 Oesophagus in the lower part.
4 Diaphragm..
terior
1 Vertebral column.
2 Herniazygos veins.
Io fhe Right Side
1 Oesophagus in the upper part.
2 Azygos vein.
3 Thoracic duct.
4 Right lung and pleura (Fig. 19.3).,
To the Letl
Left lung and pleura.
Bronches
1 Nine posterior intercostal arteries on each side for
the third to eleventh intercostal spaces.
2 The subcostal artery on each side (see Fig. 14.8).
3 Two leftbronchial arteries. The rightbronchial artery
arises from the third right posterior intercostal artery.
4 Oesophageal branches, supplying the middle one-
third of the oesophagus.
Pericardial branches, to the posterior surface of the
pericardium.
Mediastinal branches, to lymph nodes and areolar
tissue of the posterior mediastinum.
Superior phrenic arteries to the posterior part of the
superior surface of the diaphragm. Branches of these
arteries anastomose with those of the musculo-
phrenic and pericardiacophrenic arteries.
PULMONARY TRUNK
The wide pulmonary trunk starts from the summit of
infundibulum of right ventricle. Both the ascending
aorta and pulmonary trunk are enclosed in a common
sleeve of serous pericardium, in front of transverse
sinus of pericardium. Pulmonary trunk carrying
deoxygenated blood, overlies the beginning of
ascending aorta. It courses to the left and divides
into right and left pulmonary arteries under the
concavity of aortic arch at the level of sternal angle
(Figs 19.2 and 19.3).
The right pulmonary artery courses to the right
behind ascending aorta, and superior vena cava and
anterior to oesophagus tobecome part of the root of the
lung. It gives off its firstbranch to the upper lobe before
entering the hilum. Within the lung the artery descends
posterolateral to.the mainbronchus and divides like the
bronchi into lobar and segmental arteries.
The left pulmonary artery passes to the left anterior
to descending thoracic aorta to become part of the root
of the left lung. At its beginning, it is connected to the
inferior aspect of arch of aorta by ligamentum arteriosus,
a remnant of ductus arteriosus. Rest of the course is same
as of the right branch.
