This artery (A. carotis externa) by its size and direction constitutes
the continuation of the common carotid. It passes forward on the lateral
wall of the pharynx at the lower border of the guttural pouch, covered
by the submaxillary gland and the stylo-maxillaris, digastricus, and
stylo-hyoideus muscles. It then emerges between the stylo-hyoideus and
the great cornu of the hyoid bone, passes upward on the latter parallel
with the posterior border of the lower jaw, and terminates about two
inches (ca. 5 cm.) below the temporo-maxillary articulation by dividing
into superficial temporal and internal maxillary branches. It is crossed
deeply near its origin by the superior laryngeal and pharyngeal branches
of the vagus nerve. Just before its emergence its superficial face is
crossed by the hypoglossal nerve, and the glosso-pharyngeal nerve passes
over its inner surface at the ventral border of the great cornu. The
chief collateral branches are the masseteric, external maxillary, and
posterior auricular. It also furnishes variable branches to the
submaxillary and parotid glands, the guttural pouch, and the pharyngeal
lymph glands, as well as twigs to some adjacent muscles.
1. The =inferior masseteric= or maxillo-muscular artery (A. masseterica
inferior) is given off from the external carotid at its emergence from
beneath the stylo-hyoideus. It passes downward and slightly forward
under cover of the parotid gland and over the tendon of insertion of the
sterno-cephalicus to the posterior border of the mandible and appears on
the masseter muscle, into which it plunges after a short course on its
surface. It gives branches also to the internal pterygoid and
stylo-maxillaris muscles and the parotid gland.
2. The =external maxillary=, =facial=, or =submaxillary artery= (A.
maxillaris externa)[159] arises from the external carotid on the inner
surface of the posterior belly of the digastricus (Fig. 436). It runs
downward and forward on the lateral wall of the pharynx across the deep
face of the stylo-hyoideus toward the great cornu of the hyoid bone,
accompanied by the glosso-pharyngeal nerve in front and the hypoglossal
nerve behind. After giving off the lingual artery at the posterior
border of the great cornu, it inclines more ventrally on the inner
surface of the internal pterygoid muscle, crosses over the hyo-glossus
muscle, the hypoglossal nerve, the submaxillary duct, and the
intermediate tendon of the digastricus, and turns forward in the
submaxillary space. Here it lies on the lower part of the internal
pterygoid muscle, and is related internally to the submaxillary lymph
glands, above to the anterior belly of the digastricus, and below to the
homonymous vein. At the anterior border of the masseter it turns around
the lower border of the jaw and runs upward on the face in front of that
muscle.[160] At the turn the artery is in front, the vein in the middle,
and the parotid duct posterior. The artery and vein pass upward along
the anterior border of the masseter, under cover of the facial
panniculus and the zygomaticus, and are crossed superficially by
branches of the facial nerve and deeply by the parotid duct. The artery
terminates over the levator labii superioris proprius by dividing into
the dorsal nasal and the angular artery of the eye. The chief branches
of the external maxillary are as follows:
(1) The =pharyngeal artery= (A. palatina ascendens) arises usually
behind the stylo-pharyngeus, passes between that muscle and the great
cornu, and runs forward on the lateral wall of the pharynx under the
elastic pharyngeal fascia. It is distributed to the soft palate,
pharynx, and tonsil.
[Illustration:
FIG. 435.—SUPERFICIAL DISSECTION OF HEAD OF HORSE. MOST OF THE
PANNICULUS IS REMOVED.
_a_, Dilatator naris superior; _b_, levator labii superioris proprius;
_c_, levator nasolabialis; _d_, dilatator naris lateralis; _e_,
buccinator; _f_, zygomaticus; _g_, depressor labii inferioris; _h_,
stump of retractor anguli oris; _i_, masseter; _k_, _k_, scutularis;
_l_, scutulo-auriculares superficiales; _m_, zygomatico-auricularis;
_n_, parotido-auricularis; _o_, stylo-maxillaris; _p_,
sterno-cephalicus; _p′_, tendon of _p_; _q_, omo-hyoideus; _r_,
splenius; _s_, tendon of splenius and trachelo-mastoideus; _t_,
corrugator supercilii; _u_, orbicularis oris; _v_, parotid gland;
_w_, zygomatic arch; _x_, scutiform cartilage; _y_, upper commissure
of nostril; _1_, facial nerve; _2_, superior buccal nerve; _3_,
inferior buccal nerve; _4_, transverse facial nerve; _5_, cervical
branch of facial nerve; _6_, posterior auricular branch of second
cervical nerve; _7_, cutaneous cervical branch of same; _8_,
infratrochlear nerve; _9_, frontal nerve; _10_, lacrimal nerve;
_10′_, end of auriculo-palpebral nerve; _11_, inferior masseteric
artery and vein; _12_, transverse facial artery and vein; _13_,
facial artery; _14_, inferior labial artery; _15_, superior labial
artery; _16_, lateral nasal artery; _17_, dorsal nasal artery; _18_,
angular artery of the eye; _19_, posterior auricular artery; _20_,
_21_, jugular vein; _22_, external maxillary vein; _23_, great
auricular vein; _24_, parotid duct; _24′_, origin of same. (After
Ellenberger-Baum, Top. Anat. d. Pferdes.)
]
(2) The =lingual artery= (A. lingualis) is a large branch which diverges
from the parent trunk at an acute angle, runs along the ventral border
of the great cornu of the hyoid bone, and dips under the hyo-glossus
muscle. It then passes across the kerato-hyoideus, turns inward under
the intercornual joint of the hyoid bone, and runs forward in the tongue
between the hyo-glossus and genio-glossus. This part (A. profunda
linguæ) is flexuous and is accompanied by branches of the hypoglossal
and lingual nerves. It is the chief artery of the tongue, and
anastomoses with the opposite artery and the sublingual.
(3) The =sublingual artery= (A. sublingualis) is a smaller vessel which
arises at the anterior extremity of the submaxillary gland (Fig. 436).
It passes forward on the anterior belly of the digastricus between the
ramus of the mandible and the mylo-hyoideus, perforates the latter, runs
along the lower border of the sublingual gland, and ramifies in the
mucous membrane of the anterior part of the floor of the mouth. It
detaches branches to the muscles and skin in the submaxillary space, the
submaxillary lymph glands, and the sublingual gland. It also gives off
the small =submental artery=, which runs forward superficially toward
the lower lip, supplying twigs to the skin and the mylo-hyoideus.
[Illustration:
FIG. 436.—PAROTID, MASSETERIC, AND LINGUAL REGIONS OF HORSE: DEEP
DISSECTION, THIRD LAYER.
_a_, Mylo-hyoideus, anterior part, reflected; _b_, genio-hyoideus;
_c_, genio-glossus; _d_, sublingual gland; _e_, ramus of mandible,
the greater part of which is removed; _e′_, stump of masseter; _f_,
maxillary tuberosity; _g_, great cornu of hyoid bone; _h_, wing of
atlas; _i_, intermediate tendon of digastricus; _i′_, anterior
belly, _i″_, posterior belly of digastricus; _k_, posterior part of
mylo-hyoideus; _l_, hyo-glossus; _m_, pterygoideus internus (cut);
_n_, stylo-hyoideus; _o_, stylo-maxillaris (cut); _p_,
crico-pharyngeus; _q_, obliquus capitis ant.; _r_, tendon of
trachelo-mastoideus; _s_, rectus cap. ant. major; _t_,
mastoido-humeralis (cut); _u_, sterno-cephalicus (cut); _v_,
sterno-thyroideus (cut); _w_, sterno-hyoideus (cut); _x_,
omo-hyoideus; _y_, obliquus cap. post.; _z_, splenius (cut); _1–4_,
upper cheek teeth; _4′_, last cheek tooth; _5_, stump of facial
nerve; _6_, stump of buccinator nerve; _7_, lingual nerve; _7′_,
superficial branch, _7″_, deep branch of lingual nerve; _8_, stumps
of inferior alveolar artery, vein and nerve; _9_, mylo-hyoid nerve
(cut); _10_, glosso-pharyngeal nerve; _11_, hypoglossal nerve; _12_,
superior laryngeal nerve; _13_, ventral branch of first cervical
nerve; _14_, vagus and sympathetic; _15_, dorsal branch of spinal
accessory nerve; _16_, ventral branch of same; _17_, inferior
cerebral vein; _18_, submaxillary duct; _19_, common carotid artery;
_20_, parotid branch; _21_, thyro-laryngeal artery; _22_, pharyngeal
artery; _23_, laryngeal artery; _24_, internal carotid artery; _25_,
occipital artery; _26_, external carotid artery; _27–31_, external
maxillary artery; _28_, posterior palatine artery; _29_, lingual
artery; _30_, sublingual artery; _32_, internal maxillary artery;
_33_, internal maxillary vein (origin); _34_, remnant of parotid
gland; _35_, thyroid gland; _36_, jugular vein; _37_, pharyngeal
lymph glands. (After Ellenberger-Baum, Top. Anat. d. Pferdes.)
]
In some cases the sublingual artery arises from the lingual and the
submental from the external maxillary. Sometimes the sublingual
remains on the external face of the mylo-hyoideus—thus resembling the
submental of man—and the sublingual gland is supplied by a special
branch of the lingual.
Not uncommonly a considerable branch, given off in the submaxillary
space, turns round the lower border of the jaw and enters the middle
of the lower part of the masseter muscle. In some cases this artery is
of large size and its pulsation can be felt. It is accompanied by a
vein.
(4) The =inferior labial artery= (A. labialis inferior) arises from the
facial a little before it reaches the depressor labii inferioris (Fig.
435). It passes forward, dips under the depressor muscle, and continues
to the lower lip. It supplies branches to the muscles and skin in this
region, to the inferior buccal glands, the mucous membrane of the cheek,
and the lower lip, anastomosing with the mental artery and the
corresponding vessels of the opposite side. It detaches a branch (A.
anguli oris) to the angle of the mouth, which anastomoses with the
superior labial.
(5) The =superior labial artery= (A. labialis superior) arises from the
facial in front of the facial crest (Fig. 435). It passes forward under
the dilatator naris lateralis and levator nasolabialis to the upper lip,
gives twigs to the upper part of the cheek and the lateral nasal region,
and ramifies in the upper lip, anastomosing with the opposite artery and
the palato-labial.
(6) The =lateral nasal artery= (A. lateralis nasi) arises usually a
little above the preceding one, and runs forward parallel with it and
under the levator nasolabialis to the nostril (Fig. 435). It supplies
branches to the lateral nasal region and the nostril.
The vessel is often double. It may arise from the superior labial at
the point of bifurcation of the facial or with the dorsal nasal from
the infraorbital artery (as in the ox). In some cases it gives off a
dorsal nasal branch.
(7) The =dorsal nasal artery= (A. dorsalis nasi) arises on the levator
labii superioris proprius and passes forward under the levator
nasolabialis to the dorsum nasi (Fig. 435).
(8) The =angular artery of the eye= (A. angularis oculi) runs toward the
internal canthus of the eye, where it anastomoses with the orbital
branch (Ramus malaris) of the infraorbital artery (Fig. 435).
In addition to the preceding, unnamed branches are supplied to the
submaxillary salivary gland and the submaxillary lymph glands.
3. The =posterior auricular artery= (A. auricularis posterior) arises at
an acute angle from the external carotid just above the origin of the
masseteric. It passes upward under cover of the parotid gland, to which
it gives branches, and divides into several branches which supply the
skin and muscles of the external ear (Fig. 435). The =posterior branch=
passes to the posterior part of the base of the ear, where it divides
into two branches; of these, one (Ramus intermedius) passes up the
convex surface of the external ear to the apex, while the other (Ramus
medialis) winds around to the anterior (inner) border, and forms an arch
with the intermediate branch. The =external branch= (Ramus lateralis)
passes up the posterior (external) border of the ear and forms an arch
with the intermediate branch. The =deep branch= (A. auricularis
profunda) enters the interval between the external auditory canal and
mastoid process, and passes through an opening into the interior of the
external ear and ramifies in the skin which lines it. It gives off the
=stylo-mastoid artery=, which passes through the stylo-mastoid foramen
into the tympanum, forms an arch around the membrana tympani, and
supplies the middle ear and its muscles.