The masseter and superficial muscles and the parotid gland are in
great part removed. _a_, _a_, Levator labii superioris proprius;
_b_, _b_, levator nasolabialis; _c_, dilatator naris inferior; _d_,
buccinator; _e_, common mass of buccinator and depressor labii
inferioris; _f_, depressor labii inferioris; _g_, masseter; _h_,
orbicularis oculi; _i_, temporalis; _k_, occipito-hyoideus; _k′_,
stylo-maxillaris; _l_, sterno-cephalicus; _l′_, tendon of same; _m_,
omo-hyoideus; _n_, crico-pharyngeus; _o_, mastoid tendon of
mastoido-humeralis; _p_, splenius; _q_, inferior buccal and labial
glands; _r_, superior buccal glands; _s_, remnant of parotid gland;
_t_, submaxillary gland; _u_, anterior cervical (subparotid) lymph
glands; _v_, probe passed into diverticulum nasi; _w_, cornu of alar
cartilage; _x_, internal palpebral ligament; _y_, wing of atlas;
_z_, scutiform cartilage of ear; _1_, external nasal nerve; _2_,
anterior nasal nerve; _3_, superior labial nerve; _4_, anterior part
of superior buccal nerve; _5_, buccinator nerve; _6_, _6′_, inferior
alveolar nerve; _6″_, mental nerve-continuation of _6_; _7_,
masseteric nerve; _8_, facial nerve (cut); _9_, superficial temporal
nerve; _10_, anastomosis between _9_ and _8_; _11_, internal
auricular nerve; _12_, posterior auricular nerve; _13_, digastric
nerve; _14_, cervical branch of facial nerve (cut); _15_,
auriculo-palpebral nerve; _16_, lacrimal nerve; _17_, frontal nerve;
_18_, infratrochlear nerve; _19_, n. zygomaticus s. subcutaneus
malæ; _20_, spinal accessory nerve; _21_, ventral branch of spinal
accessory nerve (to sterno-cephalicus); _22_, ventral end branch of
first cervical nerve; _23_, thyro-laryngeal artery; _24_, internal
maxillary artery; _25_, masseteric artery; _26_, great (posterior)
auricular artery; _27_, external branch of _26_; _28_, deep
auricular artery; _29_, superficial temporal artery; _30_,
transverse facial artery; _31_, facial artery; _32_, inferior labial
artery; _33_, superior labial artery; _34_, lateral nasal artery;
_35_, dorsal nasal artery; _36_, angular artery of eye; _37_, labial
twigs of palato-labial artery—left uncolored by oversight; _38_,
branch of buccinator artery; _39_, buccinator vein; _40_, vena
reflexa; _41_, _42_, jugular vein; _43_, external maxillary vein;
_44_, inferior cerebral vein; _45_, stump of great auricular vein;
_46_, ramus of mandible; _47_, facial crest; _48_, zygomatic arch;
_49_, parotid duct. (After Ellenberger-Baum, Top. Anat. d. Pferdes.)
]
(3) The =lesser= or =posterior palatine nerve= (N. palatinus minor s.
posterior), also termed the staphyline, is much the smallest of the
three branches (Figs. 438, 439). It passes downward and forward with the
palatine vein in the groove at the inner side of the tuber maxillare and
ramifies in the soft palate.
The sphenopalatine ganglia and plexus (Fig. 515) lie on the
perpendicular part of the palate bone and the pterygoid process under
cover of the maxillary nerve. The afferent fibers of the plexus and
ganglia come chiefly from the branches of the sphenopalatine nerve and
the nerve of the pterygoid canal. Interspersed in these are several
minute ganglia and one or more larger ones. The =nerve of the
pterygoid canal= or =Vidian nerve= (N. canalis pterygoidei) is formed
by the union of sympathetic fibers with the superficial petrosal
branch of the facial nerve. It passes forward at first between the
Eustachian tube and the sphenoid bone, enters the canal between the
pterygoid bone and process, and joins the posterior part of the
plexus. It is probable that it furnishes the motor fibers to the
levator palati and palatinus muscles. Efferent filaments go to the
periorbita and the ophthalmic vessels, and others accompany the
branches of the maxillary nerve, around which they have a plexiform
arrangement.
3. The =infraorbital nerve= (N. infraorbitalis) is the continuation of
the maxillary trunk. It traverses the infraorbital canal, emerges
through the infraorbital foramen, and divides into nasal and superior
labial branches. Along its course it gives off =superior alveolar= or
=dental branches= (Rami alveolares maxillæ), which supply the teeth,
alveolar periosteum, and gums.
The delicate posterior alveolar branches are given off in the
pterygo-palatine fossa, pass through small foramina in the tuber
maxillare, and supply the posterior molar teeth and the maxillary
sinus. The middle alveolar branches are given off in the infraorbital
canal, and constitute the chief nerve-supply to the cheek teeth and
the maxillary sinus. The anterior or incisor branch runs forward in
the anterior alveolar or incisor canal and supplies branches to the
canine and incisor teeth. The foregoing unite with each other to form
the superior dental plexus, from which the dental and gingival
branches are given off.
The =external nasal branches= (Rami nasales externi), two or three in
number, accompany the levator labii superioris proprius and ramify in
the dorsum nasi and the nasal diverticulum.
The large =anterior nasal branch= (Ramus nasalis anterior) passes over
the nasal process of the premaxilla under cover of the dilatator naris
inferior, gives branches to the nasal mucous membrane, and terminates in
the skin of the upper lip.
The =superior labial branch= (Ramus labialis dorsalis) is the largest of
the terminals of the infraorbital nerve. It passes downward and forward
under the levator nasolabialis and, after supplying the skin of the
anterior part of the cheek, forms a rich terminal ramification in the
skin and mucous membrane of the upper lip. It anastomoses with the
superior buccal branch of the facial nerve.
III. The =mandibular nerve= (N. mandibularis), also termed the inferior
maxillary branch, is formed by the union of two roots; of these the
large sensory root comes from the semilunar ganglion, and the small
motor root is the pars minor of the trigeminus. It emerges from the
cranium through the oval notch of the foramen lacerum, between the
temporal wing of the sphenoid bone and the muscular process of the
petrous temporal, and gives off the following branches:
1. The =masseteric nerve= (N. massetericus) (Figs. 437, 515) passes
outward through the sigmoid notch of the mandible and enters the deep
face of the masseter muscle, in which it ramifies.
2. The =deep temporal nerves= (Nn. temporales profundi) (Fig. 437), two
or three in number, arise by a common trunk with the masseteric. They
supply the temporal muscle.
3. The =buccinator nerve= (N. buccinatorius) passes obliquely forward
through the anterior part of the external pterygoid muscle, then between
the internal pterygoid and the tuber maxillare (Fig. 514). It continues
forward in the submucous tissue of the cheek along the lower border of
the buccinator and divides into branches which ramify in the mucous
membrane and glands of the lips in the vicinity of the commissure. It
supplies small branches to the external pterygoid and temporal muscles
and detaches numerous collateral twigs to the mucous membrane of the
cheek and to the buccal glands. It also communicates with the inferior
buccal branch of the facial nerve.
4. The =pterygoid nerve= (N. pterygoideus) arises in common with the
preceding, passes forward on the guttural pouch, and divides into
branches for the pterygoid muscles (Fig. 515).
The =otic ganglion= (G. oticum) is situated near the origin of the
pterygoid and buccinator nerves, and is related internally to the tensor
palati and the Eustachian tube. It receives motor fibers from the
pterygoid nerve and sensory fibers by the small superficial petrosal
nerve from the tympanic plexus, through which communications are made
with the facial and glosso-pharyngeal nerves. Sympathetic fibers are
derived from the plexus on the internal maxillary artery. Efferent
filaments go to the tensor palati, tensor tympani, and pterygoid
muscles, and to the Eustachian tube.
The ganglion is small and somewhat difficult to demonstrate. In many
cases it is replaced by a number of minute ganglia interspersed in a
fine plexus.
5. The =superficial temporal nerve= (N. temporalis superficialis) (Figs.
437, 514, 515) runs outward across the pterygoideus externus, passes
between the parotid gland and the neck of the ramus of the mandible,
turns around the latter, and divides into two branches. The upper branch
(Ramus transversus faciei) accompanies the transverse facial vessels and
ramifies in the skin of the cheek. The larger inferior branch unites
with the inferior buccal division of the facial nerve.
[Illustration:
FIG. 515.—DEEP DISSECTION OF BASE OF CRANIUM, VIEWED FROM THE RIGHT
AND BELOW.
The tympanic cavity is opened and the paramastoid process is sawn off.
_a_, Occipital condyle; _b_, body of sphenoid; _c_, external
auditory meatus (part removed); _d_, malleus; _e_, incus; _1_, stump
of ophthalmic nerve; _2_, maxillary nerve (cut off); _3_,
sphenopalatine plexus; _4_, Vidian nerve; _4′_, deep petrosal nerve;
_4″_, branch to tympanic plexus; _4‴_, superficial petrosal nerve;
_5_, superficial temporal nerve (cut off); _6_, masseteric nerve
(cut off); _7_, mandibular nerve (raised); _8_, lingual nerve (cut
off); _9_, pterygoid nerve (cut); _10_, nerve to tensor tympani;
_11_, otic ganglion; _12_, facial nerve; _13_, stapedial nerve;
_14_, chorda tympani; _15_, glosso-pharyngeal nerve (cut); _16_,
tympanic nerve; _17_, vagus (cut off); _18_, auricular branch of
vagus; _19_, spinal accessory nerve (cut off); _20_, hypoglossal
nerve (cut off); _21_, sympathetic nerve (cut off); _22_, internal
carotid artery. (After Ellenberger, in Leisering’s Atlas.)
]
Before its division the nerve gives off twigs to the guttural pouch, the
parotid gland, the external ear, and the skin of the external auditory
meatus and the membrana tympani. Branches from it concur with filaments
from the cervical branch of the facial nerve in the formation of the
auricular plexus.
6. The =inferior alveolar= or =dental nerve= (N. alveolaris mandibulæ)
(Figs. 436, 437, 514) arises with the lingual by a common trunk which
passes forward at first on the external pterygoid muscle, then inclines
ventrally between the internal pterygoid and the ramus of the mandible.
The lingual and alveolar separate at an acute angle, and the latter
enters the mandibular foramen and courses in the canal within the ramus
(Fig. 516). Emerging at the mental foramen, it terminates by dividing
into six to eight inferior labial and mental branches, which ramify in
the lower lip and chin. Before entering the bone, the nerve detaches the
=mylo-hyoid nerve= (N. mylo-hyoideus), which runs downward and forward
between the ramus and the mylo-hyoid muscle; it supplies that muscle,
the anterior belly of the digastricus, and the skin of the anterior part
of the submaxillary space. The dental and gingival branches detached
from the nerve within the mandible are arranged like the corresponding
nerves of the upper jaw.
7. The =lingual nerve= (N. lingualis) arises by a common trunk with the
inferior alveolar or dental nerve (Figs. 436, 437). After separating
from the latter it runs downward and forward, lying at first between the
ramus of the mandible and the internal pterygoid muscle, then on the
inner face of the mylo-hyoid. On reaching the root of the tongue it
divides into superficial and deep branches. The =superficial branch=
(Ramus superficialis) runs forward on the stylo-glossus and accompanies
the submaxillary duct on the deep face of the sublingual gland. It
supplies the mucous membrane of the tongue and the floor of the mouth.
At the root of the tongue it gives off a recurrent branch to the isthmus
faucium, which communicates with the lingual branch of the
glosso-pharyngeal nerve. The larger =deep branch= (Ramus profundus)
turns around the lower edge of the hyo-glossus, passes upward and
forward between that muscle and the genio-glossus, and continues forward
on the latter to the tip of the tongue. It gives branches to the mucous
membrane and the fungiform papillæ of the tongue, and anastomoses with
branches of the hypoglossal nerve and with the superficial branch.
Minute ganglia occur on the finer branches of the lingual nerve. The
=chorda tympani= branch of the facial joins the lingual nerve at the
origin of the latter and is incorporated with it in its distribution to
the tongue.
[Illustration: