Thorax

1. THE AORTA
Dr M Idris Siddiqui

2. THE AORTA
• The Aorta is the largest
artery of the body which
carries the oxygenated
blood from the left
ventricle and supplies it
to all the parts of the
body.
• The aorta initially is one
inch wide in diameter.
• The aorta is classified as
a large elastic artery.

3. THE AORTA
• The aorta can be divided into four sections:
1. The ascending aorta,
2. The aortic arch, Thoracic aorta
3. The thoracic (descending) aorta,
4. The abdominal aorta.
• The first 3 parts are confined to the thoracic cavity
and together create the thoracic aorta.
– It terminates at the level of L4 by bifurcating into the left
and right common iliac arteries.

4. ASCENDING AORTA ORIGIN AND COURSE
• A. Ascending aorta originates from the upper end of
the left ventricle (i.e., aortic vestibule) and
continues as an arch of aorta at the sternal angle.
• B. It is about 5 cm long and its diameter is about 3
cm. It is completely enclosed in the pericardium.
• C. Lies inside the pericardium(in the middle
mediastinum) below the level of sternal angle.
– It begins at the level of the lower border of left 3rd
costal cartilage, runs upwards, forwards and to the right
to continue as the arch of aorta at the level of sternal
angle.

5. AORTIC SINUSES (SINUSES OF THE VALSALVA)
• The root of aorta presents 3 dilatations termed aortic
sinuses of Valsalva. These dilatations are just above the
cusps of the aortic valve. These positions are:
– Anterior , left posterior, and right posterior.
• A. Anterior aortic sinus supplies origin to the right
coronary artery, therefore it is also named right
coronary sinus.
• B. Left posterior aortic sinus supplies origin to the left
coronary artery, therefore it is also referred to as left
coronary sinus.
• C. Right posterior aortic sinus is called non-coronary
sinus.

6. Ascending Aorta
• Aortic bulb is a bulge in the right wall of the
ascending aorta at its union with all the arch of the
aorta
• Branches:
• The left and right aortic sinuses are dilations in the
ascending aorta, located at the level of the aortic
valve. These give rise to:
• The left coronary artery
• The right coronary artery
– These supply the myocardium.

7. Relations of Ascending Aorta
ANTERIOR: From below upwards these are as follows:
A. Infundibulum of right ventricle.
B. Pulmonary trunk.
C. Pericardium
POSTERIOR: From before backwards and to right these are as follows:
A. Transverse sinus of pericardium.
B. Right pulmonary artery.
C. Right principal bronchus
TO THE RIGHT: A. Right atrium.
B. Superior vena cava.
TO THE LEFT: A. Left atrium.
B. Pulmonary trunk.

8. DEVELOPMENT
• The ascending aorta develops
from the truncus arteriosus
after its partition by the spiral
septum.

9. Aneurysm of ascending aorta
• It takes place at the bulb of the ascending aorta.
• The bulb of aorta is a dilatation in the right wall
of ascending aorta that is subjected to constant
thrust of the forceful blood current ejected from
the left ventricle.
• It might compress the right atrium, SVC or right
principal bronchus.
• Its rupture (a serious complication) leads to
accumulation of blood in the pericardial cavity
(hemopericardium).

10. Aortic Arch
• Its location is in the superior mediastinum.
• The aortic arch is a continuation of the ascending
aorta and begins at the level of the second
sternocostal joint.
• It arches superiorly, posteriorly and to the left
before moving inferiorly.
• The aortic arch ends at the level of the T4 vertebra
i.e. at level of sternal angle.
• The arch is still connected to the pulmonary trunk
by the ligamentum arteriosum.
– Remnant of the foetal ductus arteriosus

11. Branches of the arch of aorta
• There are three major branches arising from the
aortic arch.
• Proximal to distal:
– Brachiocephalic trunk: The first and largest branch that
ascends laterally to split into the right common carotid
and right subclavian arteries. These arteries supply the
right side of the head and neck, and the right upper
limb.
– Left common carotid artery: Supplies the left side of the
head and neck.
– Left subclavian artery: Supplies the left upper limb.

12. ARCH
OF
AORTA

14. Points to be noted in the course of
arch of aorta
• A. The arch of aorta arches over the root
of left lung.
• B. It begins and ends at the same level,
i.e., at sternal angle.
• C. It begins anteriorly and ends
posteriorly.

15. RELATIONS OF ARCH OF AORTA
ANTERIOR AND TO THE LEFT: A. Left lung and pleura.
B. Left phrenic nerve.
C. Left vagus nerve.
D. Left cardiac nerves
E. Left superior intercostal vein.
POSTERIOR AND TO THE RIGHT: A. Trachea.
B. Esophagus.
C. Left recurrent laryngeal nerve.
D. Thoracic duct.
E. Vertebral column.
SUPERIOR: A. Brachiocephalic trunk.
B. Left common carotid artery.
C. Left subclavian artery.
D. Left brachiocephalic vein.
E. Thymus.
INFERIOR: A. Left bronchus.
B. Bifurcation of pulmonary trunk.
C. Ligamentum arteriosum.
D. Left recurrent laryngeal nerve.
E. Superficial cardiac plexus.

17. BRANCHES
• A. Brachiocephalic (innominate) artery.
• B. Left common carotid artery.
• C. Left subclavian artery.
• Occasionally, a fourth branch referred to
as thyroidea ima artery may originate
from the arch of aorta.

19. Brachiocephalic trunk
• There is only one brachiocephalic trunk; from the
aortic arch.
• The brachiocephalic artery arises opposite the
centre of manubrium, ascends upwards, backwards
and to the right.
• The brachiocephalic artery ends behind the right
sternoclavicular joint by dividing into:
– Right subclavian artery
– Right common carotid artery.

21. LEFT SUBCLAVIAN ARTERIES
• It is found below the clavicle that is why it is called subcalvian
artery.
• It runs upwards on the left mediastinal pleura and makes groove
on the left lung and enters the neck by passing behind the left
sternoclavicular joint
– The left subclavian artery has thoracic in addition to cervical parts.
• The subclavian artery arches laterally across the anterior surface
of the cervical pleura onto the very first rib posterior to the
scalenus anterior muscle.
• At the outer border of 1st rib, it finishes by becoming axillary
artery.
• It is split into 3 parts by the scalenus anterior muscle. These are:
– First part-goes from origin to medial border of scalenus anterior.
– Second part-is located behind the scalenus anterior muscle.
– Third part-goes from the lateral border of scalenus anterior to the
outer border of the very first rib.

23. LEFT COMMON CAROTID ARTERIES
• There are 2 common carotid arteries: left and right.
– These are the main arteries of the head and neck.
• The left common carotid artery originates directly from
the arch of aorta in thorax (superior mediastinum).
• It ascends to the back of left sternoclavicular joint and
enters the neck.
• The left common carotid artery runs upwards from left
sternoclavicular joint to the upper border of the lamina
of thyroid cartilage .
• Opposite the disk between the 3rd and 4th cervical vertebrae.
– To the left it is related to the left lung and on a posterior
plane to the left phrenic and vagus nerve (and left subclavian
artery)

25. DEVELOPMENT
• The arch of aorta develops from the following
sources:
– A. Aortic sac.
– B. Left horn of aortic sac.
– C. Left fourth aortic arch artery.
– D. Left dorsal aorta (between the connection of
the fourth aortic arch(artery) and 7th cervical
intersegmental artery)

26. AORTIC KNUCKLE
• In X-ray chest (PA view), the shadow of arch
of aorta appears as small bulb-like
projection in the upper end of the left
margin of the cardiac shadow termed aortic
knuckle.
• The aortic knuckle may become notable in
old age because of undue folding of the arch
caused by atherosclerosis.

27. COARCTATION OF AORTA
• It is congenital narrowing of the aorta just proximal or
distal to the entrance of the ductus arteriosus.
Accordingly it is named preductal type and postductal
type of coarctation of aorta, respectively. It probably
takes place because of hyper involution of the ductus
arteriosus.
• Clinical features:
• A. There is difference in the blood pressure of the
upper and lower limbs (i.e., high blood pressure in
upper limbs and low unrecordable blood pressure in
the lower limbs).
• B. Notching of the lower borders of the ribs because
of dilatation of engorged posterior intercostal arteries.
• C. Pulsating scapulae.

28. PATENT DUCTUS ARTERIOSUS
• In foetal life, pulmonary trunk is connected to the
arch of aorta (just distal to the origin of left
subclavian artery) by short wide channel termed
ductus arteriosus.
• Normally, after beginning, it closes functionally
inside a week and anatomically inside 4 to 12
weeks.
• The obliterated ductus arteriosus is named
ligamentum arteriosum. Non-obliterated ductus
arteriosus is referred to as patent ductus
arteriosus.

29. ANEURYSM OF THE ARCH OF AORTA
• It is the localized dilatation of the arch
and causes compression of neighboring
structures in the superior
mediastinumproducing mediastinal
syndrome.
• The characteristic clinical sign in this
condition is a tracheal-tuga that is a
feeling of tugging sensation in
the suprasternal notch.

30. DESCENDING AORTA
• The descending aorta is the section of the thoracic
aorta which is contained in the posterior
mediastinum.
• It originates leveled along with the lower boundary
of the T4 vertebra, consistent with the aortic arch,
and also terminates anterior to the lower boundary
of the T12 vertebra within the aortic hiatus.
• it initially begins to the left of the vertebral column
but approaches the midline as it descends. It leaves
the thorax via the aortic hiatus in the diaphragm,
and becomes the abdominal aorta.

31. Branches of the thoracic aorta
• In descending order:
– It possesses six paired branches
1. Bronchial arteries:
2. Mediastinal arteries:
3. Oesophageal arteries:
4. Pericardial arteries:
5. Superior phrenic arteries:
6. Intercostal and subcostal arteries:

32. Development
The majority of the descending aorta is
created through the combination of
the primitive dorsal aortae.
In embryos around 2-6 mm. long, having
twenty-three mesodermal somites, the
primitive dorsal aorta; are merged with
each other through the tenth to the
sixteenth section.
On a later stage the fusion is carried on
backwards towards the twenty-third
body section the level of the fourth
lumbar vertebra exactly where
the common iliac arteries emerge.
Still later the small terminal sections of
the primitive dorsal aorta merge with
each other to create the
unpaired middle sacral artery, which
ends on the termination of the
coccygeal region.

33. Relations of the thoracic aorta
In front of it: From above downwards:
1. The left bronchus & the root of left lung.
2. The pericrdium over the base of the heart.
3. The esophagus.
4. The diaphragm.
Behind it: 1. The bodies of thoracic vertebrae T5,6,7 lie on its right side while the bodies
of lower five thoracic vertebrae(from T8 to T12) lie behind it.
2. The superior hemiazygos vein crosses behind it at the level of T8.
3. The inferior hemiazygos vein crosses ehind it at level of T9.
On its right: 1. Two structures lie on the right posterolateral side of the descending aorta
along its whole length;
• these are azygos vein & the thoracic duct.
2. The esophagus lies to the right side of the upper part of the descending
aorta(opposite T5,6,7).
3. The mediastinal surface of the lung on the right side of its lower part.
On its left: The left mediastinal pleura and left lung.

34. Branches of the thoracic aorta
Branches Origin and course
Pericardial
branches
A few small vessels to the posterior surface of the pericardial sac
Bronchial
branches
Vary in number, size, and origin-usually, two left bronchial arteries from the
thoracic aorta and one rightbronchial artery from the third posterior
intercostal artery or the upper left bronchial artery
Esophageal
branches
Four or five vessels from the anterior aspect of the thoracic aorta, which form
a continuous anastomotic chain-anastomotic connections include esophageal
branches of the inferior thyroid artery superiorly, and esophageal branches of
the left inferior phrenic and the left gastric arteries inferiorly
Mediastinal
branches
Several small branches supplying lymph nodes, vessels, nerves, and areolar
tissue in the posterior mediastinum
Posterior
intercostal
arteries
Usually nine pairs of vessels branching from the posterior surface of the
thoracic aorta-usually supply lower nine intercostal spaces (first two spaces
are supplied by the supreme intercostal artery-a branch of the costo-cervical
trunk)
Superior phrenic
arteries
Small vessels from the lower part of the thoracic aorta supplying the posterior
part of the superior surface of the diaphragm-they anastomose with the
musculophrenic and pericardiacophrenic arteries
Subcostal artery The lowest pair of branches from the thoracic aorta located inferior to rib XII

36. SURFACE ANATOMY
• The descending thoracic aorta might
be protruded as a 2.5 cm wide strap
via the sternal termination of the
second left costal cartilage into a
median placement 2 cm over
the trans-pyloric plane on the first
lumbar vertebra.