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The Veins
Dr.Pardeep kumar
Introduction:
 The veins convey the blood from the
different parts of the body to the
heart.
 The capillaries converge into very
small vessels called venules, which,
in turn, join to form larger vessels
called veins. The major veins return
blood to the atria of the heart.
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After the blood leaves the capillaries, its pressure
continues to drop; it is lowest near the right
atrium of the heart in the superior and inferior
venae cavae. With the progressive change from
capillaries to venules to veins, the diameters of
individual vessels and the thickness of their walls
steadily increase, whereas the total crosssectional area of parallel vessels decreases.
Venous pressure is always lower than arterial
pressure, and the walls of the veins are never as
thick as the walls of the corresponding arteries.
The veins consist of the pulmonary and systemic
ones.
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The characteristics of the veins are as
follows:
1) The rate of flow of the blood in veins
being slower than in the arteries.
2) Veins are larger and more numerous
than the corresponding arteries so that
the blood delivered to tissues can be
adequately returned to the heart.
3) Venous valve: Most veins are provided
with valves which serve to prevent the
reflux of the blood. The valves are very
numerous in the veins of the extremities,
especially in the veins of lower limbs,
these veins having to conduct the blood
against the force of gravity in addition to
being subjected to intermittent pressure
due to muscular contractions
4) The systemic veins can be divided into
the superficial and deep veins.
 The superficial veins, which lie just
beneath the skin (in the superficial fascia,
in the hypodermis, immediately under the
skin), return blood from the skin and the
subcutaneous regions to the deep
veins.They freely anastomose with one
another, and they also communicate with
the deep veins.
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The deep veins accompany the arteries.
Most of the deep veins travel alongside an
artery and have the same name as the
artery. Accompanying the smaller arteries,
as the radial, ulnar, brachial, tibial, or
peroneal, the deep veins exist generally in
pairs, one lying on each side of the artery,
and are called venae comitantes. In
certain regions, however, the deep veins
do not accompany the arteries.
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5) The anastomoses between veins are more
numerous.
6) Specific structural veins includes sinus of dura
mater and diploic vein.
Venous sinuses are not actually vessels, but are
spaces that collect blood in certain regions and
return it to the veins. The walls of venous sinuses
are composed of connective tissue, with no
muscle present, and they are lined with
endothelium that is continuous with the
endothelium of the capillaries and veins.
Larger venous sinuses are located in the dura
mater, the outer meningeal covering of the brain.
Ⅰ. The Veins of Pulmonary
Circulation
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The pulmonary veins are four in
number, two from each lung, and are
devoid of valves.
They return the oxygenated blood
from the lungs, perforate the fibrous
layer of the pericardium and open
separately into the upper and
posterior part of the left atrium of
the heart.
Ⅱ. The Veins of Systemic
Circulation
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They may be arranged into three groups,
The superior vena cava and its tributaries
The inferior vena cava and its tributaries
The veins of the heart.
Ⅰ) The System of Superior Vena
Cava

It includes the superior vena cava
and its tributaries. It collects the
blood from the head and neck, the
upper limbs, the wall and some
organs (with the exception of heart
and lungs) of the thorax, and a
portion of the upper part of the wall
of the abdomen.
The superior vena cava
 It is formed by the
junction of two
brachiocephalic
(innominate) veins behind
the lower border of the
first right costal cartilage
close to the sternum, and
has no valves. It descends
vertically on the right of
the ascending aorta, and
ends in the upper part of
the right atrium opposite
the third costal cartilage.
Brachiocephalic
(innominate) veins
 They are two large trunks.
Each is formed, behind
the sternal end of the
clavicle, by the union of
the internal jugular and
subclavian veins of its
side.
 The angle of the union is
termed the venous
angle.
 The tributaries of the
brachiocephalic veins are
 the vertebral
 internal thoracic
 inferior thyroid veins.
The internal jugular vein

It collects the blood from
the brain, superficial parts
of the face and neck. It
begins at the skull in the
jugular foramen, as a direct
continuation of the sigmoid
sinus, runs downwards
through the neck within the
carotid sheath, and behind
the sternoclavicular joint,
unites with the subclavian
vein to form the
brachiocephalic vein.
The chief extracranial
tributaries of the internal
jugular vein are:
① The facial vein
 It begins at the medial
angle of the eye, and
runs obliquely
downwards and
backwards behind the
facial artery. A little
below the angle of the
mandible it is joined by
the anterior branch of
retromandibular vein.
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The communication with
cavernous sinus:
The facial vein has no
valves and it
communicates with the
cavernous sinus by two
routes:
a. firstly, through
connections directly with
the ophthalmic vein,
b. secondly, by the deep
facial vein, which links it
to pterygoid plexus and
hence also to the
cavernous sinus.
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Thus infective thrombosis of the
facial vein may extend into the
intracranial venous sinuses.
hence, the territory of the facial
veins around the nose and the upper
lip is frequently termed the “danger
area” of the face.
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② Retromandibular vein
It is formed by the union of
the superficial temporal vein
and maxillary vein.
It descends in the substance
of the parotid gland, and
divides into two branches:
an anterior which passes
forwards and unites the
facial vein,
a posterior which is joined
by posterior auricular vein to
form the external jugular
vein.
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Pterygoid plexus:
The pterygoid plexus is
placed between the temporalis
and pterygoid muscles.
It anastomoses with the facial
vein through the deep facial
vein; it is also connected with
the cavernous sinus by veins
which pass through the
emissary foramen.
The maxillary vein begins in
the pterygoid plexus.
In addition, the internal
jugular vein receives the veins
of the tongue, the superior
and middle thyroid veins, and
the pharyngeal veins.
2) The subclavian vein
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It is the continuation of the axillary vein.
Its tributaries are the external jugular vein,
and sometimes the anterior jugular vein.
The external jugular vein:
The external jugular vein is formed by
the union of the posterior division of the
retromandibular vein with the posterior
auricular vein. It runs down the neck,
crosses the sternocleidomastoid obliquely,
and in the supraclavicular triangle
perforates the deep fascia to end in the
subclavian vein.
3) The veins of upper limb
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They are divided into two sets,
superficial and deep, which
anastomose freely with each other.
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① The superficial veins of
upper limb
They are placed
immediately under the
skin, in the superficial
fascia.
They are the
Cephalic
Basilic
median cubital veins,
and their tributaries.
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The cephalic vein begins in the radial
part of the dorsal venous rete of hand and
winds upwards round the radial border of
the forearm to its anterior surface; it then
ascends subcutaneously along the lateral
side of the forearm and arm to the upper
one-third of the arm, where it lies in the
groove between the pectoralis major and
deltoid, and pierces the deep fascia to end
in the axillary vein or subclavian vein.
The basilic vein begins in the ulnar part
of the dorsal venous rete of hand.
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It runs up for some distance
on the posterior surface of
the ulnar side of the forearm
but inclines forwards to the
anterior surface below the
elbow; it then ascends
medial to biceps, and
perforates the deep fascia a
little below the middle of the
arm to end in the brachial
vein.
The median cubital vein is
given off from the cephalic
vein below the front of the
elbow, and passes medially
to join the basilic vein.
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Significance:
Blood sampling and transfusion, and
intravenous injection in general, are
often performed at the bend of the
elbow, the largest vein, usually the
median cubital vein, is commonly
selected.
3. The azygos vein
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It begins as the continuation of the right
ascending lumbar vein. It ascends along
the right side of the thoracic vertebrae to
the fourth thoracic vertebra, where it
arches forwards over the root of the right
lung to end in the superior vena cava.
The azygos vein receives the posterior
intercostal veins of the right side, the
hemiazygos and accessory hemiazygos
and the right bronchial veins.
1) The hemiazygos vein
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It begins as the continuation of the left
ascending lumbar vein. It ascends on the
left of the thoracic vertebrae as high as
the eighth thoracic vertebra, then passes
across the column to end in the azygos
vein.
The hemiazygos vein receives the lower
posterior intercostal and subcostal veins of
the left side, the accessory hemiazygos
vein and some esophageal veins.
2) The accessory hemiazygos
vein
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It descends on the left side of the
vertebral column, corsses the body
of the seventh thoracic vertebra and
joins the azygos vein, sometimes
joins the hemiazygos veins.
The accessory hemiazygos vein
receives the left fourth to eighth
posterior intercostal veins.
3) The veins of spinal column
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The external vertebral plexus.
The internal vertebral plexus.
Ⅱ) The System of Inferior Vena
Cava
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It includes the inferior vena cava and
its tributaries. It collects the venous
blood from the lower part of the
body.
1. The inferior vena cava
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It is the largest venous trunk which
conveys blood to the right atrium of
the heart from all the body below the
diaphragm.
It is formed by junction of the two
common iliac veins anterior to the
fifth lumbar vertebra, a little to the
right.
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It ascends in front of the
vertebral column, on the
right side of the
abdominal aorta.
Reaching the liver it is
contained in the sulcus
for inferior vena cava on
its posterior surface. It
then passes the vena
caval foramen of the
diaphragm, and pierces
the fibrous pericardium
to open into the lower
posterior part of the
right atrium.
2. The common iliac vein

It is formed by the union of the
external and internal iliac veins, in
front of the sacroiliac joint; passing
obliquely upwards, it ends on the
right side of the fifth lumbar vertebra
by uniting with opposite one at an
acute angle to form the inferior vena
cava.
1) The internal iliac vein
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Like arteries, the tributaries of the
internal iliac vein can be divided into
parietal and visceral.
The visceral tributaries begin in the
venous plexuses which surround the
rectum, bladder, prostate, uterus
and vagina.
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The rectal plexus consists of two parts, an
internal in the submucosa and an external
outside the muscular coat of the rectum
and anal canal. The two parts
communicate freely with each other.
The external plexus is drained by the anal
veins into the internal pudendal vein, the
inferior rectal vein into the internal iliac
vein, and the superior rectal into the
inferior mesenteric vein.
2) The external iliac vein
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It is the upward continuation of the
femoral vein, and begins behind the
inguinal ligament.
It collects the blood from the lower
limb and the lower portion of the
abdominal wall.
3) The veins of lower limb
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They can be divided, like those of the
upper limb, into two sets, superficial
and deep; the superficial veins are
immediately under the skin in
superficial fascia, the deep veins
accompany the arteries.
① The superficial veins of
lower limb
 They are the great and
small saphenous veins and
their tributaries.
 The small saphenous
vein
 It begins in the dorsal
venous arch of foot, at the
lateral margin of the foot,
passes behind the lateral
malleolus, ascends along
the midline of the back of
the leg, perforates the
deep fascial in the lower
part of the popliteal fossa,
and ends in the popliteal
vein.
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The great saphenous vein
It begins in the dorsal venous arch of foot,
at the medial margin of the foot, passes in
front of the medial malleolus, and ascends
along the medial side of the leg to the
knee.
It runs upwards posteromedial to the
medial condyle of the femur and along the
medial side of the thigh to the saphenous
hiatus, where it drains into the femoral
vein.
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Before perforating the cribriform fascia of
the saphenous hiatus it receives the
flowing superficial:
The superficial epigastric vein,
The superficial iliac circumflex vein,
The external pudendal vein,
The superficial medial femoral vein,
The superficial lateral femoral vein.
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The saphenous veins
frequently become
dilated and tortuous,
called the varicose vein.
In operating upon
varicose vein all the
tributaries at the groin
have to be ligated as
well as the main
saphenous trunk; if one
tributary escapes, it in
turn becomes dilated
and produces
recurrence of the
varicose.
② The deep veins of lower limb
 They accompany the arteries and
their branches and are similarly
named. The veins of the foot and leg
are generally in pairs.
3. The tribuaries of the inferior vena
cava
They are also divided into parietal
and visceral.
1) The parietal tributaries
 They are the inferior phrenic and
lumbar veins, which accompany the
corresponding arteries.
 The lumbar veins are connected by a
longitudinal vessel which is termed
the ascending lumbar vein.
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2) The visceral tributaries
① The testicular veins
They issue from the testis and epididymis
and form a convoluted plexus, called the
pampiniform plexus, the chief constituents
of the spermatic cord.
The right testicular vein opens into the
inferior vena cave, and the left testicular
veins opens into the left renal vein at a
right angle.
The ovarian veins in the female
correspond with the testicular veins in the
male.
② The renal veins
 They issue from the hilum of each kidney,
and open into the inferior vena cava
almost at a right angle. The left is thrice
the length of the right.
③ The suprarenal veins
 They accompany the middle suprarenal
arteries. The right opens into the inferior
vena cava, and the left into the left renal
vein.
④ The hepatic veins
 They are usually three in
number, the right, middle
and left, collect the blood
which has passed through
the liver from the hepatic
portal vein and hepatic
artery.
 They emerge from the
posterior surface of the
liver and open immediately
into the inferior vena cava
as it lies in the groove on
the posterior surface of the
liver.
Hepatic portal venous system
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It constitutes the hepatic
portal vein and its tributaries.
It includes all the veins
collecting the blood from the
abdominal part of the
alimentary tract (with the
exception of the lower part of
the anal canal) and from the
spleen, pancreas and
gallbladder.
From these viscera the blood is
conveyed into the liver by the
hepatic portal vein. In the
liver this vein ramifies like an
artery and ends in capillarylike vessels termed sinusoids.
1)The characteristics of the hepatic portal
venous system
① The blood of the portal system passes
through two sets of “exchange” vessels:
the capillaries of the alimentary tract,
spleen, pancreas and gallbladder; and
the sinusoids of the liver.
② The hepatic portal vein and its
tributaries have no valves.
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2) The formation of the hepatic portal vein
The hepatic portal vein is formed by the junction
of the superior mesenteric and splenic veins,
behind the neck of pancreas.
It is about 6—8 cm long, passes upwards behind
the first part of the duodenum, then ascends in
the right border of the lesser omentum to reach
the right end of the porta hepatis where it divides
into right and left stems, which accompany the
corresponding branches of the proper hepatic
artery into the substance of the liver.
In the lesser omentum it is placed behind the
common bile duct and the proper hepatic artery,
the former lying to the right of the latter.
3) The tributaries of the hepatic portal vein
① The superior mesenteric vein
 It receives the veins from the organs
supplied by the branches of the superior
mesenteric and gastroduodenal arteries.
② The splenic vein
 It drains the short gastric, left
gastroepiploic, the pancreatic and the
inferior mesenteric veins.
③ The inferior mesenteric vein
 Its tributaries correspond to the
branches of the inferior mesenteric
artery.
④ The left gastric vein
⑤ The right gastric vein
⑥ The cystic vein
⑦ The paraumbilical veins
4) The anastomoses between the
hepatic portal venous system and
vena caval system
 These anastomoses, which may
collectively offer an effective
collateral circulation in case of
obstruction of the hepatic portal vein,
are as follows:
① The esophageal venous plexus
 In the abdominal part of the esophagus,
tributaries of the left gastric vein (portal
drainage) anastomose with the
esophageal tributaries of the azygos veins
(superior vena caval drainage), viz.
 Hepatic portal v. →Left gastric v.
→Esophageal venous plexus →esophageal
tributaries →azygos v. →Superior vena
cava.
② The rectal venous plexus
 In the wall of the anal canal, the superior
rectal vein (portal drainage) anastomoses
with the inferior rectal vein (inferior vena
caval drainage), viz.
 Hepatic portal v. →Splenic v. →Inferior
mesenteric v. →Superior rectal v. →Rectal
venous plexus →inferior rectal and anal v.
→Internal iliac v. →Common iliac v.
→Inferior vena cava.
③ The periumbilical venous network
 At the umbilicus, the fine
paraumbilical veins (portal drainage)
anastomose with the superificial and
deep epigastric vein (caval drainage).
Viz.
 Hepatic portal v. →Paraumbilical v.
→Periumbilical venous network →the
following routes:
a) Superficial epigastric v. →Great
saphenous v. →Femoral v. →External iliac
v. Common iliac v. →inferior vena cava.
b) Thoracoepigastric v. →Lateral thoracic v.
→Axillary v. →Subclavian v.
Brachiocephalic v. →Superior vena cava.
C) Superior epigastric v. →Internal
thoracic v. →Brachiocephalic v. →Superior
vena cava.
d) Inferior epigastric v. →External iliac v.
→Common iliac v. →Inferior vena cava.
④ The internal and external vertebral
plexus
 Hepatic portal v. →superior and
inferior mesenteric veins→small
veins of the posterior abdominal
wall→internal and external vertebral
plexus→posterior intercostal veins
and lumbar veins→inferior vena cava.
5) The clinical significance
 Normally, the hepatic portal venous
blood traverses the liver and empties
into the inferior vena cava.
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This pathway may be obstructed by
various causes, e.g., the pressure of a
tumor on the hepatic portal vein, the
cirrhosis of liver, the valvular disease of
the heart.
In this condition, the portal venous
pressure rises and collateral pathways
open up between the portal and caval
venous systems. The anastomotic veins
then become dilated and varicose and
they may even rupture to lead to a fatal
hematemesis or hematochezia.
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The varicose veins are called the
esophageal varices in the esophagus, the
hemorrhoids in the rectum, and the “caput
meusae” around the umbilicus.
Some success has been achieved in case
of portal obstruction by anastomosis of
the portal vein to the inferior vena cava,
of the splenic vein to the left renal vein,
after removal of the spleen.