The =jugular veins= (Vv. jugulares), right and left (Fig. 431), arise
behind the posterior border of the lower jaw about two and a half inches
(ca. 6 to 7 cm.) below the temporo-maxillary articulation by the union
of the superficial temporal and internal maxillary veins. Each passes
downward and backward, at first embedded more or less in the parotid
gland, and continues in the jugular furrow to the thoracic inlet, where
it unites with its fellow and the two brachial veins to form the
anterior vena cava. In the neck it is covered by the skin, fascia, and
panniculus, and is superficial to the carotid artery, from which it is
separated in the anterior two-thirds of the region by the omo-hyoideus
muscle.[170] It contains valves at the mouths of its tributaries and has
several pairs of semilunar valves variably disposed along its course.
Its tributaries are as follows:
1. The =internal maxillary vein= (V. maxillaris interna) is larger than
the external maxillary. It may be considered to begin as the
continuation backward of the buccinator vein where the vessel crosses
the alveolar border of the mandible (about two inches (ca. 5 cm.) behind
the last molar tooth). It runs backward on the inner surface of the
ramus below the external pterygoid and covered by the internal pterygoid
muscle for a distance of about three inches (ca. 7 to 8 cm.), then
inclines a little downward and runs ventral to the artery for about an
inch (ca. 2 to 3 cm.). It crosses the external face of the artery at the
posterior border of the jaw, and is joined by the superficial temporal
vein to form the jugular. Its principal radicles are:
(1) The =dorsal lingual vein= (V. dorsalis linguæ), which is a satellite
of the lingual nerve.
(2) The =inferior alveolar= or =dental vein= (V. alveolaris mandibulæ),
a satellite of the corresponding artery. It often unites with the
preceding.
(3) =Pterygoid veins= (Rami pterygoidei).
(4) The =deep temporal vein= (V. temporalis profunda) is a large vessel
which receives tributaries from the temporalis muscle and emissaries
from the parieto-temporal canal. It is connected with the anterior
cerebral vein and usually with the meningeal veins by its frontal
branch. The latter drains chiefly the lacrimal gland and passes behind
the supraorbital process.
2. The =superficial temporal vein= (V. temporalis superficialis) is a
satellite of the corresponding artery. It is formed by the confluence of
the =anterior auricular= and =transverse facial veins=. The former
receives the =superior cerebral vein= (V. cerebralis dorsalis), which is
the emissary of the transverse sinus of the dura mater; it emerges from
the parieto-temporal canal behind the postglenoid process. The
=transverse facial vein= (V. transversa faciei) runs at first above the
artery of like name, then plunges deeply into the masseter and unites in
front with the facial vein. It is connected with the vena reflexa.
3. The =inferior masseteric= or =maxillo-muscular vein= (V. masseterica)
joins the jugular at the upper border of the sterno-cephalicus tendon.
It is a short trunk formed by the confluence at the posterior border of
the jaw of masseteric and pterygoid veins. The former is usually
connected by a large branch with the buccinator vein.
[Illustration:
FIG. 461.—SUPERFICIAL VESSELS AND NERVES OF HEAD AND ANTERIOR PART OF
NECK OF HORSE.
_a_, Masseter; _b_, parotid gland; _c_, parotido-auricularis; _1_,
masseteric artery; _2_, parotid branch; _3_, transverse facial
artery; _4_, facial artery; _5_, _6_, inferior labial artery; _7_,
superior labial artery; _8_, lateral nasal artery; _9_, infraorbital
artery; _10_, dorsal nasal artery; _11_, angular artery of eye;
_12_, _13_, jugular vein; _14_, great auricular vein; _15_,
masseteric vein; _16_, superficial temporal vein; _17_, transverse
facial vein; _17′_, deep temporal vein; _18_, external maxillary
vein; _19_, facial vein; _20_, labial vein; _21_, dorsal nasal vein;
_22_, lateral nasal vein; _23_, angular vein of eye; _24_, _25_,
facial nerve; _25′_, _25″_, superior and inferior buccal nerves;
_26_, transverse facial nerve; _27_, auriculo-palpebral nerve; _28_,
anterior auricular nerve; _29_, cervical branch of facial nerve;
_30_, ventral branch of second cervical nerve; _30′_, _30″_, _30‴_,
auricular and cutaneous branches of _30_; _31_, branches of dorsal
division of first and second cervical nerves; _32_, dorsal branch of
spinal accessory nerve. (After Leisering’s Atlas.)
]
4. The =great auricular vein= (V. auricularis magna) is a satellite of
the posterior auricular artery above, but joins the jugular a variable
distance below and behind the point of origin of the artery.
5. The =inferior cerebral vein= (V. cerebralis ventralis) is an emissary
of the cavernous sinus of the dura. It is a satellite of the internal
carotid artery, receives the =condyloid vein=, and joins the jugular
near the occipital vein or by a common trunk with it.
6. The =occipital vein= (V. occipitalis) arises in the fossa atlantis by
the union of muscular and cerebrospinal branches. The former comes from
the muscles of the poll and passes through the foramen transversarium.
The latter is connected with the occipital sinus of the dura mater and
emerges from the spinal canal by the intervertebral foramen.
7. The =external maxillary= or =facial vein= (V. maxillaris externa)
arises by radicles which correspond in general to the branches of the
artery of like name. It passes down over the cheek along the anterior
border of the masseter muscle behind the artery, crossing over the
parotid duct, which lies behind the vein lower down. Thus on the ramus
and as they turn around its lower border the artery is in front, the
vein in the middle, and the duct posterior. In the submaxillary space
the vein is ventral to the artery for some distance, then parts company
with the artery, runs straight backward along the lower border of the
parotid gland, and opens into the jugular vein at the posterior angle of
the gland.[171] The chief differences in the tributaries of the vein as
compared with the branches of the corresponding artery are as follows:
The =labial veins= (Vv. labiales) form a plexus in the submucous tissue
of the cheek from which two veins emerge. The upper one passes back and
joins the buccinator vein. The lower one (V. labialis communis) joins
the external maxillary vein.
Three veins connect with the external maxillary at the anterior border
of the masseter.
The upper one is the =transverse facial=, which unites close to the end
of the facial crest.
A little lower is the large valveless =vena reflexa= or =alveolar vein=.
This passes back under the upper part of the masseter on the maxilla,
turns around the tuber maxillare, perforates the periorbita, and joins
the ophthalmic vein. It is relatively small at each end, but presents
one or two large fusiform dilatations. It receives the following
tributaries: (_a_) The =palatine vein= (V. palatina major), which
separates from the palatine artery at the anterior palatine foramen and
passes in the groove between the tuber maxillare and the palate bone.
The palatine veins form a very rich plexus of valveless vessels in the
submucosa of the hard palate, which consists of several layers
anteriorly. (_b_) The =sphenopalatine vein= (V. sphenopalatina) forms a
rich plexus of valveless vessels on the turbinal bones and the septum
nasi. It is usually joined by the =infraorbital vein= (V.
infraorbitalis) to form a short common trunk.
[Illustration:
FIG. 462.—DISSECTION OF SUBMAXILLARY SPACE AND ADJACENT PART OF NECK
OF HORSE.
_a_, Ramus of mandible; _b_, sterno-cephalicus muscle; _c_, _c′_,
omo-hyoidei and sterno-hyoidei (portion removed on right side); _d_,
hyoid bone; _e_, anterior belly of digastricus; _f_, _g_,
mylo-hyoideus; _h_, submaxillary lymph glands (portion removed on
right side); _i_, parotid gland; _k_, submaxillary gland; _l_, chin;
_m_, stylo-maxillaris; _1_, parotid duct; _2_, facial vein; _3_,
facial artery; _4_, external maxillary vein; _5_, sublingual vein;
_6_, sublingual artery; _7_, ventral branch of first cervical nerve;
_8_, mylo-hyoid nerve. (After Ellenberger, in Leisering’s Atlas.)
]
The venous plexuses are remarkably developed in certain parts of the
nasal mucosa. On the septum a little below its middle and on the
turbinals the veins are in several layers. The olfactory region does
not share in this arrangement and the veins here are small and join
the ethmoidal vein.
(_c_) The =ophthalmic vein= (V. ophthalmica) is a short trunk, connected
in front with the vena reflexa and behind with the cavernous sinus
through the foramen lacerum orbitale. It receives veins which correspond
to the arterial branches.
The =buccinator vein= (V. buccinatoria) extends backward from the
external maxillary along the lower border of the depressor labii
inferioris and buccinator under cover of the masseter, passes between
the ramus of the mandible and the tuber maxillare and is continued as
the internal maxillary vein. It has a large fusiform dilatation and is
valveless. It receives a large common labial vein from the labial
plexus, and is usually connected with the masseteric vein.
[Illustration: