603
CHAPTER FIFTEEN
Cardiovascular System
The
azygos
(az
ı˘-gos)
vein
originates in the dorsal
abdominal wall and ascends through the mediastinum on the
right side of the vertebral column to join the superior vena
cava. It drains most of the muscular tissue in the abdominal
and thoracic walls.
Tributaries of the azygos vein include the
posterior
intercostal veins
on the right side, which drain the intercos-
tal spaces, and the
superior
and
inferior hemiazygos veins,
which receive blood from the posterior intercostal veins
on the left. The right and left
ascending lumbar veins,
with
tributaries that include vessels from the lumbar and sacral
regions, also connect to the azygos system.
Veins from the Abdominal Viscera
Veins carry blood directly to the atria of the heart, except
those that drain the abdominal viscera
(f g. 15.55)
. They
originate in the capillary networks of the stomach, intes-
tines, pancreas, and spleen and carry blood from these
organs through a
hepatic portal
(por
tal)
vein
to the liver
(f g. 15.56)
. There the blood enters capillary-like
hepatic
sinusoids
(he
˘-pat
ik si
nu
˘-soidz). This unique venous path-
way is called the
hepatic portal system.
The tributaries of the hepatic portal vein include the fol-
lowing vessels:
1. Right and left
gastric veins
from the stomach.
2.
Superior mesenteric vein
from the small intestine,
ascending colon, and transverse colon.
The
basilic
(bah-sil
ik)
vein
passes along the back of the
forearm on the ulnar side for a distance and then curves for-
ward to the anterior surface below the elbow. It continues
ascending on the medial side until it reaches the middle of
the arm. There it deeply penetrates the tissues and joins the
brachial vein.
As the basilic and brachial veins merge, they
form the
axillary vein.
The
cephalic
(se
˘-fal
ik)
vein
courses upward on the lat-
eral side of the upper limb from the hand to the shoulder. In
the shoulder, it pierces the tissues and joins the axillary vein,
which beyond the axilla becomes the
subclavian vein.
In the bend of the elbow, a
median cubital vein
ascends
from the cephalic vein on the lateral side of the forearm to
the basilic vein on the medial side. This large vein is usually
visible. It is often used as a site for
venipuncture,
when it is
necessary to remove a sample of blood for examination or to
add fl uids to the blood.
Veins from the Abdominal and
Thoracic Walls
Tributaries of the brachiocephalic and azygos veins drain
the abdominal and thoracic walls. For example, the
brachio-
cephalic vein
receives blood from the
internal thoracic vein,
which generally drains the tissues the internal thoracic artery
supplies. Some
intercostal veins
also empty into the brachio-
cephalic vein
(f
g. 15.54)
.
External jugular v.
Subclavian v.
Superior vena cava
Axillary v.
Brachial v.
Basilic v.
Azygos v.
Internal jugular v.
Brachiocephalic vv.
Cephalic v.
Superior hemiazygos v.
Posterior intercostal v.
Inferior hemiazygos v.
FIGURE 15.54
Veins that drain the thoracic wall. (
v.
stands for vein,
vv.
stands for veins.)
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