The =anterior vena cava= (V. cava cranialis) returns to the heart the
blood from the head, neck, thoracic limbs, and the greater part of the
thoracic wall. It is formed at the ventral part of the thoracic inlet by
the confluence of the two jugular and two brachial veins. Its origin is
attached to the first pair of ribs. It passes backward in the anterior
mediastinum, at first median and ventral to the common carotid trunk,
then deviates to the right of the anterior aorta, and opens into the
right atrium opposite to the third rib. The demarcation between vein and
atrium is not very distinct. It contains no valves except at the mouths
of its radicles. Its length is about five to six inches (ca. 12 to 15
cm.) and its caliber about two inches (ca. 5 cm.) in a subject of medium
size. Its right face is crossed by the right phrenic nerve, and on the
left it is related to the anterior aorta and brachiocephalic artery. It
receives, in addition to small pericardial and mediastinal veins, the
following tributaries:
1. The =internal thoracic vein= (V. thoracica interna) is a satellite of
the artery of that name. It opens into the anterior vena cava at the
first rib.
2. The =vertebral vein= (V. vertebralis) corresponds to the homonymous
artery. On the right side it terminates either in front of the deep
cervical vein or by a short common trunk with it. On the left side it
almost always unites with the deep cervical and vertebral vein to form a
common trunk.
3. The =deep= or =superior cervical vein= (V. cervicalis profunda)
corresponds to the artery. On the right side it leaves the artery at the
first intercostal space, crosses the right face of the trachea and opens
into the vena cava; it may form a common trunk with the dorsal or
vertebral. On the left side there is nearly always a common trunk for
all three.
4. The =dorsal vein= (V. costo-cervicalis) corresponds to the artery. On
the right side it leaves the artery on entering the thorax, crosses the
right face of the trachea, and opens into the vena cava in front of the
deep cervical or by a common trunk with it. On the left side it almost
always joins the deep cervical and vertebral to form a short common
trunk which crosses the left face of the intrathoracic part of the
brachial artery opposite the second rib and opens into the anterior vena
cava.