The arrangement of the veins is, of course, correlated in general with
the arterial system, but a few special features are worthy of mention.
The =anterior vena cava= is formed by the junction of short right and
=left brachiocephalic= (or subclavian) =veins=, and each of the latter
results from the confluence of =jugular= and =brachial veins=.
The =vena azygos= resembles that of the horse, and receives at the ninth
or tenth thoracic vertebra a =vena hemiazygos=.
Two =jugular veins= are present on each side. The =external jugular
vein= is formed by the union of external and internal maxillary veins at
the posterior border of the submaxillary gland. The two external
jugulars are commonly united by a transverse branch below the cricoid
cartilage. Each passes along the neck on the sterno-cephalicus, covered
only by the skin and panniculus, dips under the cleido-cervicalis, and
joins the internal jugular.
The =external maxillary vein= arises on the lateral nasal region by the
junction of the dorsal nasal vein with the angularis oculi. Near the
infraorbital foramen it receives the lateral nasal vein, and a little
lower the superior labial. In its course along the anterior border of
the masseter it receives the vena reflexa, which arises in the
pterygo-palatine fossa by the junction of infraorbital, sphenopalatine,
and palatine radicles, together with a branch from the cavernous sinus.
At the lower border of the mandible it is joined by the inferior labial
vein, which receives the buccinator vein. The lingual vein is connected
with its fellow by a superficial transverse branch at the insertion of
the sterno-hyoidei. The sublingual and submental veins terminate in a
variable manner, but often form a common trunk which joins the lingual.
The =internal maxillary vein= arises from the pterygoid plexus, formed
chiefly by dorsal lingual, inferior alveolar, deep temporal, pterygoid,
and meningeal tributaries. It receives the superior cerebral, auricular,
superficial temporal, transverse facial, and masseteric veins, and often
a trunk formed by the union of the inferior cerebral and occipital
veins.
The =internal jugular vein= results usually from the junction of
laryngeal and thyroid veins, but in some cases it is formed by the
confluence of the inferior cerebral and occipital veins.
The =brachial= and =radial veins= are satellites of the arteries.
The =ulnar vein= is usually double. It unites below the carpus with a
branch of the interosseous vein to form the superficial venous arch.
The =cephalic vein= accompanies the ulnar artery in the forearm and
joins the superficial venous arch below.
The =accessory cephalic vein= arises from the union of three dorsal
metatarsal veins. It joins the cephalic about the middle of the forearm.
There are three short =volar metacarpal veins= which open into the
superficial venous arch. They are formed above the metacarpo-phalangeal
joints by the junction of the =volar digital veins=, of which there are
two for each of the chief digits. The volar vein of the first digit
joins the superficial venous arch.
Each of the chief digits has two =dorsal digital veins=, while the first
digit has one.
The =posterior vena cava=, its collateral affluents, and common iliac
radicles present no special features of importance.
The =internal iliac vein= corresponds in regard to its tributaries with
the branches of the artery, except that it is not divided into dorsal
and ventral branches.
The =external iliac=, =femoral=, and =popliteal veins= with their
collateral tributaries are satellites of the arteries.
The =anterior tibial vein= is usually double, and the =posterior tibial
vein= is very small.
The =internal saphenous vein= is the upward continuation of the internal
plantar metatarsal vein. It communicates by a large branch with the
dorsal metatarsal vein, and ascends the leg as a satellite of the
saphenous artery and its plantar (posterior) branch. The =recurrent
tarsal= or =external saphenous vein= is larger. It is formed at the
lower part of the leg by the union of dorsal and external plantar
metatarsal veins, crosses the outer surface of the leg obliquely upward
and backward, ascends behind the gastrocnemius and joins the posterior
femoral vein.
The =metatarsal= and =digital veins= resemble in general the
corresponding vessels of the fore limb.