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No. 16
Section 3 The Arteries
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Upon leaving the heart, the blood enters
the vascular system, which is composed of
numerous blood vessels. The vessels
transport the blood to all parts of the body,
permit the exchange of nutrients,
metabolic end products, hormones, and
other substances between the blood and
the interstitial fluid, and ultimately return
the blood to the heart.
The vessels of the circulatory system can
be divided into two separate circuits, each
of which leaves and returns to the heart.
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The pulmonary circuit carries blood
from the right side of the heart (right
ventricle) to the lungs and back to
the left side of the heart (left atrium).
The systemic circuit carries blood
that has just left the pulmonary
circuit (from the left ventricle) to the
rest of the body and back to the
right side of the heart (right atrium).

Vessels called arteries carry blood
away from the heart. Compares to
the other types of blood vessels,
arteries must be able to withstand
the greatest internal pressure. The
major arteries divide into smaller
arteries, then into still smaller
arterioles, and finally into tiny
capillaries.
Ⅰ. The Arteries of Pulmonary
Circulation
Ⅰ) The Pulmonary Artery and its
Branches
 The pulmonary trunk conveys
deoxygenated blood from the right
ventricle of the heart to the lungs. In
the concavity of the aortic arch it
divides into right and left pulmonary
arteries.
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The right pulmonary artery runs
to the hilum of the right lung, where
it divides into three branches to
distribute to the corresponding lobes
of the lung.
The left pulmonary artery runs to
the hilum of the left lung, where it
divides into two branches, one for
each lobe of the lung.
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Ⅱ) The arterial Ligament
The left pulmonary artery is connected to the
concavity of the aortic arch by a fibrous cord,
termed the arterial ligament, which is found as
the ductus arteriosus in the fetus. During fetal
life, most of the blood in the pulmonary trunk
passes through the ductus arteriosus into the
aorta. After birth, the lumen of the ductus is
gradually obliterated and it is transformed into
the arterial ligament.
Occasionally the ductus arteriosus fails to close.
In this acse tying the ductus is often successful in
alleviating the condition.
Ⅱ. The Arteries of Systemic
Circulation
Ⅰ) The Aorta
 It is main trunk of the series of
arteries which convey the
oxygenated blood to the tissue of the
body. For convenience, it is described
in three portions, the ascending
aorta, the aortic arch and the
descending aorta.
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1. The ascending aorta (ascending part of
aorta)
Route:
It begins at the base of the left ventricle, at a
level with the lower border of the third costal
cartilage, passes obliquely upwards, forwards and
to the right. As high as the upper border of the
second right costal cartilage, it continues with the
aortic arch.
Branches:
The only branches of the ascending aorta are
coronary arteries.
2. The aortic arch
 Route:
 It begins at the level of the second right
sternocostal joint, and runs at first upwards,
backwards and to the left in front of trachea, it is
then directed backwards on the left side of the
trachea, and finally passes downwards on the left
side of the body of fourth thoracic vertebra, at
the lower border of which it is continuous with
the descending aorta.
 Branches:
 Three branches are given off from the highest
part of the aortic arch.
From right to left:
1) The brachiocephalic trunk
(innominate artery)
 It passes obliquely upwards, backwards
and to the right, at the level of the right
sternoclavicular joint, it divides into the
right common carotid and right subclavian
arteries.
2) The left common carotid artery
3) The left subclavian artery

3. The descending aorta (descending
part of aorta)
 It is divided into two portions, the thoracic
aorta and the abdominal aorta.
1) The thoracic aorta
 It is contained in the posterior
mediastinum. It begins at the level of the
lower border of the fourth thoracic
vertebra, where it is continuous with the
aortic arch, and ends in front of the lower
border of the twelfth thoracic vertebra at
the aortic hiatus of the diaphragm.
2) The abdominal aorta
 It begins at the aortic hiatus of the
diaphragm, in front of the lower
border of the body of the last
thoracic vertebra, descends in front
of the vertebral column, and ends on
the body of the fourth lumbar
vertebra by dividing into two
common iliac arteries.
Ⅱ) The Arteries of Head and Neck
 The blood supply of the head and
neck is chiefly from the branches of
the common carotid arteries and
partly from those of the subclavian
arteries.
1. The common carotid arteries
 The right common carotid artery begins at
bifurcation of the brachiocephalic trunk
behind the right sternoclavicular joint,
while the left common carotid artery
springs from the aortic arch.
 Each passes obliquely upwards and
slightly laterally, along the side of the
trachea and esophagus, to the level of the
upper border of the thyroid cartilage,
where it divides into the external and
internal carotid arteries.
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Carotid sinus and carotid body
A dilatation at the point of the bifurcation
of common carotid artery is known as the
carotid sinus, which usually involves,
and may be restricted to the proximal part
of the internal carotid artery. It acts as a
pressure-receptor which is part of the
blood pressure regulating mechanism. It
reacts to changes of the arterial blood
pressure reflexly.
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A small, reddish-brown structure
behind the point of division of the
common carotid artery is termed the
carotid body which acts as a
chemoreceptor. It responds to
changes in the composition of the
blood, particularly the oxygen-carbon
dioxide ratio.
1) The internal carotid artery
 It ascends along the pharynx to the
base of the skull, and enters the
cranial cavity through the carotid
canal without giving off branches in
the neck. This is the major artery to
the brain and other intracranial and
orbital structures.
2) The external carotid artery
 It begins oppsite the upper border of the
thyroid cartilage, and, gaking a slightly
curved course, passes upwards and
forwards, and then inclines backwards to a
point behind the neck of mandible, where,
in the substance of the parotid gland, it
divides into the superficial temporal and
maxillary arteries.

Its main branches are as follows:
①The superior thyroid artery
It supplies the adjacent muscles and the
thyroid gland.
Branch:
 Superior laryngeal artery
 It accompanies the internal branch of the
superior laryngeal nerve and pierces the
thyrohyoid membrane to supply the larynx.

② The lingual artery
 It is the principal vessel of the tongue and
the structures on the floor of the mouth.
③ The facial artery
 It supplies the submandibular gland, the
tonsil and the structures of the face.
④ The occipital artery
 It arises from the back of the external
carotid artery, opposite to the facial artery,
and runs upwards and backwards to the
posterior part of the scalp.
⑤ The maxillary artery
 It is the larger terminal branch of the
external carotid artery, arises behind the
neck of the mandible and is at first
embedded in the parotid gland. It passes
forwards to the infratemporal fossa, and
supplies the upper and lower jaws, teeth
and gums, the muscles of mastication, the
palate, the nasal cavity and the paranasal
sinuses.

The middle meningeal artery is the
most important branch of the maxillary
artery. It ascends to the base of the skull
to pass into the cranial cavity through the
foramen spoinosum. Its branches fan out
to supply the cerebral dura mater. Injury
of this artery as in the case of cranial bone
fracture in temporal region may result in
the epidural haematoma.
⑥ The superficial temporal artery
 It is the smaller terminal branch of the
external carotid artery, ascends over the
zygomatic arch, and enters the
superfiacial fascia of the temporal region.
Many branches ramify over the temporal,
auricular, zygomatic and facial regions
from which the arteries receive their
names.
2. The subclavian artery
 The right subclavian artery arises from the
brachiocephalic trunk; the left, from the
aortic arch. Each artery emerges from the
superior aperture of the thorax. It ascends
to the root of the neck and then arches
laterally across the front of the cervical
pleura and passes between the scalenus
anterior and the scalenus medius to the
outer border of the first rib, where it
becomes the axillary artery. Hemorrhage
of the upper limb can be controlled by
compressing the vessel downwards and
backwards against the first rib
immediately above the mid-point of the
clavicle.
Branches:
1) The vertebral artery
 It arises from the upper and posterior part
of the proximal end of the subclavian
artery. It ascends through the foramina in
the transverse processes of the upper six
cervical vertebrae, and enters the skull
through the foramen magnum.
 It supplies the brain and spinal cord.
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2) The internal thoracic (mammary)
artery
 It arises from the inferior surface of the
subclavian artery, opposite the vertebral
artery. It descends behind the cartilage of
the upper six ribs at a distance of 1.2 cm
from the lateral border of the sternum,
and at the level of the sixth intercostals
space divides into the musculophrenic
and superior epigastric arteries.
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The superior epigastric artery enters the
sheath of the rectus abdominis, at first
lying behind the muscle, then perforating
and supplying it, and anastomosing with
the inferior epigastric artery from the
external iliac artery.
The branches of the internal thoracic
artery are distributed chiefly to the
anterior thoracic and abdominal walls, the
pleura, the pericardium and the
diaphragm.
3) The thyrocervical trunk
 It is short, arises from the front of the
subclavian artery, close to the medial
border of the scalenus anterior, and
divides almost immediately into three
branches. One of them is the inferior
thyroid artery. Its branches supply the
lower part of the thyroid and parathyroid
glands, larynx, trachea and esophagus.
4) The inferior thyroid artery
5) The costocervical trunk
 They supply the first two intercostals
spaces and the muscles of the
scapular region.
Dorsal scapular artery:
Ⅲ) The Arteries of Axilla and Upper
Limb
 The subclavian artery, after giving off
its cervical branches, continues as
the great arterial stem of the upper
limb.

It is the continuation of the
subclavian artery and begins at the
outer border of the first rib, and ends
at the lower border of the teres
major, beyond which the artery takes
the name of brachial artery. Its chief
branches are:
1) The thoracoacromial artery
 It is a short branch and divides into
several branches to supply the muscles of
thorax and the scapular region.
2) The lateral thoracic artery
 It follows the lateral border of the
pectoralis minor to the side of the chest,
and supplies the serratus anterior and the
muscles of thorax, the axillary lymph
nodes and the subscapularis.
3) The subscapular artery
 It is the largest branch of the axillary
artery, usually it arises at the lower border
of the subscapularis, runs to the inferior
angle of the scapula, where it
anastomoses with the lateral thoracic and
intercostals arteries; finally it ends in the
neighbouring muscles and adjacent part of
the chest wall. After a short course it gives
off the circumflex scapular artery and
thoracodorsal artery.
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The circumflex scapular artery is generally
larger than the continuation of the subscapular. It
curves round the lateral border of the scapula,
traversing the triangular space; it enters the
infraspinous fossa, and anastomoses with the
suprascapular artery and other vessels to form an
arterial network around the scapula.
The thoracodorsal artery continues downwards
along the posterior axillary wall and is
accompanied in its course by the thoracodorsal
nerve (to the latissimus dorsi). It gives branches
to muscles of the posterior wall of the axilla.
4) The anterior humeral
circumflex artery
 It arises from the axillary at the
lower border of the subscapularis. It
runs horizontally in front of the
surgical neck of the humerus, and
anastomoses with the posterior
circumflex humeral artery.
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5) The posterior humeral circumflex
artery
It is larger than the anterior one. It arises
from the axillary at the lower border of
the subscapularis, and runs backwards
through the quadrangular space. It winds
the neck of the humerus and distributes
branches to the shoulder joint and the
adjacent muscles.
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2. The brachial artery
It is the continuation of the axillary artery.
It begins at the lower border of the tendon
of the teres major, and runs downwards
on the medial side of the biceps brachii. It
ends in the cubital fossa, opposite the
neck of the radius, by dividing into the
radial and ulnar arteries. The brachial
artery gives off branches to the muscles of
the arm and the humerus.

The deep brachial artery is a
larger branch from the brachial
artery, just below the lower border of
the teres major. It follows the radial
nerve closely, running at first
backwards between the long and
medial heads of the triceps brachii,
then along the groove for the radial
nerve. It supplies the triceps.
3. The radial artery
 It begins at the division of the brachial
artery below the bend of the elbow, and
passes along the radial side of the forearm
to the wrist, where its pulsation can
readily be felt and it is used clinically for
taking the pulse.
 Its branches are:
1) The muscular branches
2) The superficial palmar branch
3) The principal artery of theumb
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4. The ulnar artery
 It begins at the level of the neck of
the radius. Its branches are:
1) The muscular branches
2) The common interossous artery
3) The deep palmar branch
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5. The superficial palmar ch and deep
palmar arch.
1) The superficial palmar arch
Formation: It is formed mainly by the
ulnar artery, and is usually completed by
the superficial palmar branch of the radial
artery.
Location: It is covered by the palmar
aponeurosis, and lies on the flexor
tendons of the fingers. Its convexity is
placed at the level of a line drawn across
the hand from the distal border of the root
of the extended thumb.

Branches: It gives off three
common palmar digital arteries.
Each then divides into a pair of
vessels, the proper palmar digital
arteries, which run along the
contiguous sides of the index, middle,
ring and little fingers. An additional
digital branch of the arch passes to
the ulnar side of the fifth finger.
2) The deep palmar arch
 Formation: It is formed by the anastomsis
of the terminal part of the radial artery
with deep palmar branch of the ulnar
artery.
 Location: It lies upon the proximal ends of
the metacarpal bones. It is about 2 cm
proximal to the level of the superficial
palmar arch. It covered by the flexor
tendons of the finger.
 Branches: The branches of the arch supply
the bones and muscles of the hand, and
join common digital branches of the
superficial palmar arch.
Ⅳ) The Arteries of Thorax
 The are chiefly from the thoracic
aorta. For convenience, the arteries
can be divided into the parietal and
visceral branches.
1. The parietal branches
1) The posterior intercostals arteries
 There are usually nine pairs of posterior
intercostals arteries derived from the
thoracic aorta. They are distributed to the
lower nine intercostals spaces, being
supplied by the supreme insupreme
intercostals artery.
2) The subcostal arteries
 They are the last pair of arteries arising
from the thoracic aorta, in series with the
posterior intercostals arteries, but are
named subcostal because they are
situated below the twelfth rib.
 The posterior intercostals and subcostal
arteries chiefly supply the wall of thorax,
the upper part of the abdominal wall, the
spinal cord and its coverings.
2. The visceral branches
 They are the bronchial, esophageal
and pericardial arteries which supply
arterial blood to the structures for
which they are named.
Ⅴ) The Arteries of Abdomen
 The abdominal aorta is the main
trunk of the abdominal arteries.it
also has the parietal and visceral
branches.
1. The parietal branches
1) The inferior phrenic artery
 Three unpaired visceral arteries (the celiac
trunk, the superior mesenteric artery and
the inferior mesenteric artery) supply the
abdominal organs of alimentary system.
 Paired arteries are the middle suprarenal
arteries, the renal arteries, and the
testicular or ovarian arteries.
2) The lumbar arteries
2. The visceral branches
 Three unpaired visceral branches:
 The celiac trunk,
 The superior mesenteric artery,
 The inferior mesenteric artery,
 They supply the abdominal organs of
alimentary system.
 Four paires of arteries to the paires organs
(suprarenal gland, kidney)
Ⅵ) The Arteries of Pelvis
Ⅶ) The Arteries of Lower Limb