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The trigeminal nerve in the baboon.

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The Trigeminal Nerve in the Baboon'
RAYMOND F. GASSER AND D. MILLER WISE
Department of Anatomy, Louisiana State University Medical Center,
New Orleans, Louisiana 70112
ABSTRACT
The dehitive course, relations, branches and communications
of the extramedullary part of the trigeminal nerve in baboons are described and
illustrated. The nerve was dissected in five animals and the location of all related
parasympathetic ganglia was verified microscopically. Variable branching patterns were observed in some areas of the nerve field. Comparisons are made with
other primates including man.
The investigator using the baboon for
research purposes must be aware of the
differences that exist between this animal
and man. Only by knowing the detail in
the anatomy of the laboratory animal can
one interpret changes produced by experimental techniques. In recent years, the
baboon has been found to be an excellent
research animal since it responds to many
drugs in a manner similar to man, contracts many similar diseases and is hardy
in captivity where it adjusts and reproduces with little difficulty. Additional information on the anatomy of this primate
is badly needed. An understanding of the
arrangement of the trigeminal nerve of
this animal is basic to present and future
studies on the head region.
Gasser and Hendrickx ('69) reported on
the embryonic development of the nerve
in baboons but information on its definitive arrangement is scant and fragmentary.
A description of the frontal and lacrimal
branches of the ophthalmic division was
given by Lacroix ('27). Ashton and Oxnard
('58) reported briefly on the branching pattern of the maxillary division. Communications between the facial and trigeminal
nerves were delineated by Bowden, Mahran
and Godding ('60) and Gasser and Hendrickx ('67) described their embryonic development. Swindler ('67) illustrated some
of the cutaneous branches along with other
facial structures. A survey of the literature
on the peripheral nervous system of Papi0
was made by Hill ('70) which includes
some studies on the trigeminal nerve.
This paper presents the definitive course,
relations, branches and communications
ANAT. REC., 172: 511-522.
of the extramedullary part of the trigeminal nerve in baboons. This nerve is the
primary route by which sensations from
the head region reach the brain and it
brings motor impulses to the muscles of
mastication as well as several other muscles. It is essential for the distribution of
the autonomic innervation of cranial viscera. The location of the four, closely associated parasympathetic ganglia is included. Some comparisons are made with
the arrangement of the nerve in man and
other primates.
MATERIALS AND METHODS
The nerve was dissected in five heads
of the species, P a p b cynocephalus. Three
of the specimens were adults; two were
immature forms one to two years old. After
sacrifice, they were perfused with and
stored in 10% formalin. The arteries of
one specimen had been injected with red
latex. The arrangement of the dissected
nerve was recorded on drawings made
from photographs of the specimens. Tissue
that was suspected of containing ganglion
cells was processed for microscopic examination using hematoxylin and eosin or
toluidine blue stains. The location of all related ganglia was verified microscopically.
OBSERVATIONS
The arrangement of the trigeminal nerve
rootlets and ganglion will be described together but each division of the nerve with
Received Aug. 12, '71. Accepted Oct. 26, '71.
1 Supported by National Institute? of Health
FR-5376 and the Edward G. Schheder Educaf%%
Foundation.
511
512
RAYMOND F. GASSER AND D. MILLER WISE
its branches and associated ganglia will be
described separately.
Ophthalmic division
This division is the smallest of the three
and courses craniomedially from the ganglion through the superior orbital fissure
(fig. 1A). It gives off a meningeal branch
and then divides into three major branches
as i t enters the orbit.
Rootlets and ganglion
The sensory rootlets course from the
lateral aspect of the pons to the ganglion
and are approximately 5 mm in length
(fig. 1A). The motor root leaves the pons
caudal and medial to the sensory rootlets
and passes obliquely across the caudal as- Branches
1. A small meningeal (tentorial) branch
pect of the sensory rootlets and ganglion
to join the mandibular division. The gan- arises from the division just proximal to
glion has a semilunar shape with the three the superior orbital fissure. This filamentdivisions arising at its periphery. It mea- ous nerve terminates in the tentorium
sures approximately 5 x 10 mm.
cerebelli after a short craniolateral course.
1. Cerebellum
2. Trochlear n.
3.Cerebral peduncle
4. Pons
5 posterior clinoid
processes
6. oculomotor n.
7. Internal c a r o t i d a.
8.0ptic chiasma
9.Trigeminal n. r o o t
(motor r o o t d o t t e d )
10. Trigeminal ganglion
11. Optic n.
12. Frontal n.
13. Levator, pajpebrae
superioris m.
14. Superior r e c t u s m,
15. Ophthalmic n.
16. Abducens n.
17. Meningeal brs.
18. Mandibular n
19. Maxillary n.
2Q Lacrimal n.
21. Nasociliary n.
22. Ciliary ganglion
23 Glandular br of
lacrimal n.
24. Short.ciliary nn.
25. Superior oblique m.
26. ODhthalmic a. o r brs.
2% Medial rectus m.
28. Anterior ethmoidal n n.
29. Olfactory bulb
30. L a t e r a l rectus m.
31. Lacrimal gland
32. Bulb of eye
33. Lnftatrochlear nn.
34 Supratrochlear n.
35. Supraorbital nn.
36,Zygomatic brs. of
lacrimal n.
Fig. 1A Cranial view of the orbit and middle cranial fossa showing the relationships and
branches of the trigeminal ganglion and its ophthalmic division.
Fig. 1B Cranial view of the more detailed relationships around the ciliary ganglion.
BABOON TRIGEMINAL NERVE
2. The frontal nerve is the largest
branch. It travels rostrally in the craniomedial part of the orbit in close association with the trochlear nerve. As it approaches the orbital brim it divides into
two supraorbital nerves (lateral and medial) and a more medial suprcotrochlear
nerve. All of these nerves emerge from the
orbit in a groove on the frontal bone. The
supraorbital nerves course cranially for a
short distance over the supraorbital torus
and divide into many fine cutaneous rami
in the intermediate portion of the frontal
region (figs. 4, 5). The supratrochlear
nerve is more medial but also takes a
cranial direction to the skin of the frontal
region.
3. The lacrimal nerve passes ventrolaterally on the lateral aspect of the lateral
rectus muscle (fig. 1A). At the proximal
part of the muscle it divides into a medial,
glandular branch and a lateral, zygomatic
branch. The glandular branch proceeds to
the lacrimal gland. The larger zygomatic
branch courses ventrally in the craniolateral aspect of the orbit. It emerges from
the orbit through a canal located at the
junction of the zygomatic and frontal
bones, then divides into branches that
course to the skin in the lateral portion of
the frontal region and ventral portion of
the temporal region (figs. 4, 5 ) . One of
its branches occasionally communicates
with the facial nerve in the infraorbital
region.
4. The nasociliary nerve courses ventrally for a short distance and is adjacent
to the abducens nerve (fig. 1). It then
turns medially just caudal to the superior
rectus muscle and is closely associated
with the ophthalmic artery and orbital fat.
The proximal part of the medially coursing segment gives rise to a fine branch to
the ciliary ganglion. The nerve then proceeds ventromedially between the superior
oblique and medial rectus muscles where
it usually divides into two anterior ethmoidal nerves and two or three fine infratrochlear nerves. The anterior ethmoidal
nerves course medially through the ethmoid
bone to the cribriform plate where they reunite in the dura into a single bundle beneath the olfactory bulb. The common
nerve enters the nasal cavity through the
cribriform plate and immediately divides
513
into medial and lateral internal nasal
branches (fig. 3). Both branches course
toward the external nares in the roof of
the nasal cavity close to the nasal septum.
The lateral branch passes through the
junction region of the nasal bone with the
nasal cartilage to become the subcutaneous
external nasal branch. This branch innervates the skin over the cartilagenous portion of the nose. The infratrochlear nerves
emerge from the orbit by passing cranially
over the most medial portion of the orbital
brim to the skin on the root of the nose
and adjacent frontal region at the midline
(figs. 4, 5).
Ciliary ganglion
The ganglion lies between the lateral
rectus muscle and the optic nerve in a
position ventral to the ophthalmic artery
(fig. 1). It measures approximately 1 X
2 mm. The lower division of the oculomotor
nerve sends two small branches to the ganglion and the nasociliary and abducens
nerves each give a small communication.
Two very fine nerve filaments arise from
fascicles around the ophthalmic artery
branches that course to the medial portion
of the bulbus oculi. These Haments communicate with the ganglion by passing
above and below the optic nerve (fig. 1B).
Two fascicles arise from the ventral aspect
of the ganglion. Each subdivides into two
finer fascicles ( s h t ciliary nerves) that
enter the dorsal aspect of the bulbus oculi
above and below the optic nerve. Tiny
branches of the ophthalmic artery accompany the short ciliary nerves throughout their course.
Maxillary division
This division courses ventrally and
slightly medially from the trigeminal ganglion to emerge from the cranial cavity
through the foramen rotundum (fig. 1A).
It then travels in a cranioventral direction
across the pterygopalatine fossa to the
infraorbital canal where it continues as
infraorbital nerves in the floor of the orbit
(fig. 2). In the fossa, the maxillary division is in close association with the terminal branches of the maxillary artery.
Branches
1. A tiny meningeal branch arises close
to the trigeminal ganglion and travels in a
514
RAYMOND F. GASSER AND D. MILLER WISE
1. Pterygoalar foramen
2. Mandibular n.
3. Meningeal br.
4. Auriculotemporal n.
5.Chorda tympani n.
6. N. t o masseter
. Deep temporal nn.
10. Zygomatic n.
11. Pterygopalatine ganglion
12. Nasopalatine n.
13. Maxillary a.
14. Lateral pterygoid m.
15. Deep temporal n.
16. Temporalis rn. segment
17, Buccal n
18. N. t o lateral pterygoid
19. Inferior alveolar n.
20.N. t o medial pterygoid
21. Medial pterygoid m.
23 Mand ib I e
24. Lingual n.
25.Submandi bular ganglion
26.Mylohyoid m.
27.Ant belly digastric rn.
28 Buccinator m.
29.Buccal pouch
30.Mental nn.
31. Incisive br.
Fig, 2 Lateral view of the arrangement of the more proximal portion of the maxillary
and mandibular divisions.
caudolateral direction to the dura mater
(fig. 3).
2. The zygomatic nerve is variable in
its course and branching pattern. In one
of the specimens, the nerve originates from
the division in the floor of the orbit, passes
ventrolaterally into a canal in the zygomatic bone and emerges from the bone
by way of a foramen (zygomatic) to innervate the skin lateral and caudal to the
orbit (fig. 4). In another specimen, the
nerve divides near its origin into two, very
small branches. One of the branches
courses through the lateral wall of the orbit
to the ventral part of the temporal fossa
where it joins the other branch that passes
laterally through the pterygomaxillary fissure. The common nerve innervates a small
area of skin lateral and caudal to the orbit
(fig. 5). In this arrangement, a foramen
is not apparent on the outer surface of the
zygomatic bone. A third arrangement encountered is similar to that described for
man with the nerve dividing into
zygomaticofacial and zygomaticotemporal
branches. The facial branch courses
515
BABOON TRIGEMINAL NERVE
1. L,esser petrosal n.
2. N. t o tensor tympani
3.Otic ganglion
4. Mandibular n.
5,,N
t o levator veli palatini
6.N. t o medial pterygoid I?. Inf. alveolar n.
7. Communicating br:
12. Muscular brs.
8. Auriculotemporal n.
13 Tendon of digastric m.
9.Chorda tympani n.
14. Submandibular gland
10.N. t o mylohyoid
15. Facial a.
16. Styloglossus rn.
17 Submandibular ganglion
18 Lingual n.
19. Hyoglossus rn.
20. Hypoglossal n.
21. Sublingual gland
22 Su brnandibular duct
23 Mylohyoid m.
24..Ant. belly digastric m.
2,Ei:Sublingual a.
2G. Tongue
2'7. Mandible
2r3.Zygomatic n.
23 Med. pterygoid
30. Maxillary n.
31. Meningeal bt:
3.2. Pharyngeal n.
m.
33. N. of pterygoid canal
34. Pterygopalatine ganglion
35.Nasopalat ine n.
36.Orbital brs.
37;lnfraorbital nn.
38.Lat nasa 1 brs.
39.Post. sup. alveolar n.
40. Lesser palatine nn.
41. Ant. sup alveolar n.
42 Mid. sup. alveolar n.
43. Greater palatine n.
44. Incisive brs.
45. Ant. ethmoidal nn.
46.Med. int. nasal br:
47. Lat. i n t nasal br:
4 8 Ext. nasal br:
Fig. 3 Lateral view of the arrangement of the more intermediate portion of the maxillary
and mandibular divisions and the anterior ethmoidal branches of the ophthalmic division.
through the zygomatic bone and emerges
by way of a prominent foramen. The temporal branch travels through the lateral
wall of the orbit, across the temporal fossa
to the skin of the ventral part of the temporal region. The size of the cutaneous
field supplied by the zygomatic nerve appears to be inversely proportional to that
supplied by the zygomatic branch of the
lacrimal nerve. These two nerves usually
communicate with one another.
3. The pteTygopaEatine nerves are short,
medially directed fascicles that terminate
in the pterygopalatine ganglion (fig. 3 ) .
4. The posterior superior alveolar nerve
arises from the division in the pterygopalatine fossa. As it courses caudally
through the pterygomdary fissure it di-
516
RAYMOND F. GASSER AND I>. MILLER WISE
vides into two or more small rami. After
a short course, the rami enter minute foramina in the dorsal part of the maxilla
and innervate the dorsal maxillary teeth.
5. The division terminates as five or six
large fascicles which travel through the
floor of the orbit as infraorbital nerves.
These nerves become subcutaneous by
passing from the maxilla through approximately six foramina that vary in size and
location. Peripheral branches of the nerves
course to the skin of the lower eyelid,
upper lip and lateral snout (figs. 4, 5).
Plexuses are present in the infraorbital
and buccal regions that communicate with
the buccal branches of the facial nerve.
Two superior alveolar nerves (anterior and
middle) arise from the infraorbital nerves
and course through canals in the maxilla
to the rostral maxillary teeth (fig. 3).
down the septum to the incisive foramen
through which it travels to communicate
with the terminal branches of the greater
palatine nerves just behind the incisor
teeth.
lateral nasal
d. Several posterior
branches arise from the ganglion and innervate the mucosa on the dorsal part of
the large inferior concha and adjacent
areas of the nasal cavity.
e. A tiny pharyngea2 ramus travels in a
dorsal and caudal direction from the ganglion to the roof of the nasopharynx.
f. Several fine orbital branches course
cranially from the ganglion through the
inferior orbital fissure to join the orbital
nerves passing through the superior orbital
fissure.
g. The nerve of the pterygoid canal
enters the dorsal aspect of the ganglion
after passing through a bony canal.
Pterygopalatine ganglion
Mandibular division
The ganglion is housed in the pterygoThis division proceeds caudally and
palatine fossa that is dorsal to the maxilla,
caudal to the orbit and lateral to the dorsal laterally from the trigeminal ganglion to
emerge from the cranial cavity by way of
part of the nasal cavity (figs. 2, 3).
the foramen ovale (fig. 1A). Very shortly
Branches
i t divides into ventral (pars anterior) and
a. One or two greater palatine nerves dorsal (pars posterior) portions just lateral
course in a caudal and ventral direction to the auditory tube. The ventral portion
through a bony canal to reach the dorsal passes through a bony foramen (pterygopart of the hard palate. They emerge from alar) in the lateral pterygoid plate to the
the canal by way of a large foramen at the infratemporal fossa (fig. 2). Here, it dijunction of the maxillary and palatine vides into nerves primarily to the muscles
bones. The nerves branch repeatedly deep of mastication. The larger dorsal portion
to the mucosa on the roof of the oral cavity travels caudally and laterally along the
as they travel toward the incisor teeth. dorsal border of the lateral pterygoid plate.
Fine rami are given to the mucosa of the
palate and the lingual side of the maxillary Branches
gingiva before the terminal branches com- Undivided portion
municate with the nasopalatine nerve near
1. A filamentous meningeal branch
the incisive foramen.
b. A pair of much smaller lesser palatine arises before the division leaves the cranial
nerves proceeds caudally from the ganglion cavity and travels laterally to the dura
in a groove where the maxillary and mater (fig. IA).
2. The medial pterygoid nerve courses
sphenoid bones join. The nerves may either
pass through a bony canal to reach the from the deep aspect of the division in
soft palate or they course outside the bone close association with the otic ganglion.
just lateral to the junction of the palatine It is small and arises near the point where
the division bifurcates into its two portions
and maxillary bones.
c. The nasopalatine nerve arches me- (figs. 2, 3). After a short caudoventral
dially from the ganglion, deep to the mu- course from the foramen ovale it sends one
cosa in the dorsal part of the nasal cavity, branch into the lateral surface of the meto the nasal septum. It passes obliquely dial pterygoid muscle and a more medially
BABOON TRIGEMINAL NERVE
517
8. The inferioT alveolar nerve is one of
two terminal branches of the dorsal portion. It proceeds in a caudal and ventral
Ventral portion
direction on the lateral surface of the
3. The masseteric nerve is the first medial pterygoid muscle into the mandibubranch of the ventral portion and travels lar foramen (figs. 2, 3). Prior to entering
laterally, cranial to the lateral pterygoid the mandible, it gives off the mylohyoid
niuscle and mandibular notch to enter the nerve which, after coursing in a groove on
deep surface of the masseteric muscle the medial surface of the mandible, divides
(figs. 2, 4).
into several branches. The mylohyoid nerve
4. There are usually three deep temporal not only innervates the mylohyoid and annerves which vary in their relative size terior (ventral) belly of the digastric
and point of origin. All three may arise muscles but it also sends branches to the
completely from the masseteric nerve or medial pterygoid muscle and the submancompletely from the parent stem of the dibular gland and ganglion. The inferior
ventral portion or from a combination of alveolar nerve sometimes divides into two
both (fig. 2). They originate near the fascicles prior to entering the mandible.
cranial aspect of the lateral pterygoid mus- Within the mandible it breaks up into
cle and travel to the deep side of the tem- several fascicles that communicate with
.poralis muscle.
each other and send rami to the mandibu5. As the ventral portion passes deep to lar teeth. The plexus usually gives rise to
the lateral pterygoid muscle it sends a four or five mental nerves (figs. 2, 4, 5).
small lateral pterygoid nerve into the deep The size and position of these nerves vary
surface of the muscle.
but their rami regularly course to the skin
6. After the last motor nerve arises, the of the chin and lower lip and the mucosa
ventral portion of the division passes on the inner aspect of the lip. The marthrough the upper head of the lateral ginal mandibular branch of the facial
pterygoid muscle as the buccal nerve. It is nerve is closely associated with the mental
usually a single bundle that travels in a nerves but no large communications are
caudal and ventral direction through part apparent. After the mental nerves are given
of the temporalis muscle to the buccal off, the inferior alveolar nerve continues
region. However, it can separate into two within the mandible to the incisor teeth as
parts which course around portions of the the incisive branch.
temporalis muscle and then reunite (fig. 2).
9. The other terminal branch of the dorShortly after it emerges from the muscle, sal portion, the lingual nerve, takes a
it sends rami superficially to the skin and course that arches caudally and ventrally
deeper rami through the buccinator mus- on the lateral surface of the medial pterycle to the mucosa of the cheek and buccal goid muscle, sometimes passing through
pouch.
part of the muscle (figs. 2, 3 ) . The chorda
tympani nerve emerges from the skull
Dorsal portion
through a prominent petrotympanic fissure
7. The first branch of the dorsal portion and proceeds medial to the auriculotemis the auriculotemporaE nerve which travels poral and inferior alveolar nerves to join
caudolaterally, deep to the lateral pterygoid the lingual nerve. After passing the medial
muscle (figs. 2, 3). It then passes dorsally, pterygoid muscle, the lingual nerve courses
deep to the condyle and neck of the man- medially and sends several communicadible. From this location it takes a cranio- tions to the submandibular ganglion. Conlateral course through the parotid gland tinuing ventrally, it spirals around the
to become subcutaneous in front of the submandibular duct to pass medial to the
auricle. It communicates with the otic gan- sublingual gland. After branches are given
glion and the facial nerve and sends to the gland, the nerve divides into many
branches to the temporomandibular joint rami which course to the mucosa on the
body of the tongue. Several of the more
and auricle.
directed branch to the tensor veli palatini
muscle.
518
RAYMOND F. GASSER AND D. MILLER WISE
I. Auriculotemporal n.
2 Superficial temporal a.
3 P a r o t i d gland
4 Facial n.
5. Temporal br. (VII)
6. Zygomatic br (VII)
11. Supraorbital nn.
12. Supratrochlear n.
13 l n f r a t rochlear nn.
!4. Palpebral br.
25. Infraorbital n n B plexus
6 Buccal b r (VII)
17. Parotid d u c t
18. Buccal n 13, plexus
19. Facial v. G masseter m.
20.Buccal p o u c h
21. Marginal mandibular br: (VII)
2 2 E x t e r n a I nasal bc
23.Mental nn.
Fig. 4 Lateral view of the cutaneous branches of the trigeminal nerve with segments of
the facial nerve. Part of the infratemporal fossa is also exposed.
dorsal rami communicate with branches
of the hypoglossal nerve as the latter nerve
passes between the mylohyoid and hyoglossus muscles.
Otic ganglion
The ganglion is located on the medial
side of the undivided portion of the mandibular division at the lateral aspect of
the auditory tube. It is flat and measures
approximately 3 X 6 mm. Several h e fascicles attach the ganglion to the division
(fig. 3). The lesser petrosal nerve joins the
ganglion dorsally. The ganglion sends a
fine communication caudally to the auri-
culotemporal nerve and also give origin to
the very small tensor tympani nerve.
Submandibular ganglion
The ganglion is located between the
hyoglossus and mylohyoid muscles in close
association with the submandibular gland
(figs. 2, 3). Two to three communications
pass to the ganglion from the lingual nerve
as the latter nerve travels medially in front
of the medial pterygoid muscle. In addition to glandular branches, the ganglion
also sends a branch to both the mylohyoid
and medial pterygoid muscles and communicates with the mylohyoid nerve.
BABOON TRIGEMINAL NERVE
DISCUSSION
The trigeminal nerve in the baboon has
many similarities to that in man. However, the maxillary and mandibular divisions are unusually large which can be
explained by the marked prognathism that
this animal exhibits.
O'phthalmic division
The ophthalmic division is the smallest
division. Christensen ('33) reported a simi1;u situation in the rhesus monkey. A collection of neuroblasts was observed by
Gasser and Hendrickx ('69) in the medial
part of the division during embryonic development which later became scattered
and eventually disappeared. Later, during
fetal development they observed in one
54 day old specimen a well defined ganglion on the medial side of the division.
Attempts were made to locate grossly and
microscopically such a ganglion in the
adult but we were unsuccessful.
The frontal nerve was found to be the
largest branch of the division. Christensen
('33) reported the lacrimal to be the largest
branch in the rhesus monkey. Lacroix ('27)
mentioned that the frontal nerve is markedly developed in P. cynocephalus with a
small medial and a larger lateral branch
to the skin of the frontal region. Our dissections support his findings but in addition we found a smaller, more medial
supratrochlear branch of the frontal nerve
(figs. 1, 4, 5). No mention of supraorbital
or supratrochlear branches of the frontal
nerve in the rhesus monkey was made by
Christensen ('33). Raven ('50) showed
medial and lateral supraorbital branches
and one supratrochlear branch in the
1. Zygomatic n.
2 Lacrimal n., zygomatic br:
3. Supraorbital nn.
4. Supratrochlear n.
5 lnfratrochlear n n.
6. Pa I p e bra I b r
z
519
lnfraorbital nn.
8. Buccal plexus
9. lnfraorbital plexus
3 0. Facial n.
11. Marginal mandibular br:
12 Mental nn.
Fig. 5 Frontal view of the cutaneous branches of the trigeminal nerve with segments of
the facial nerve.
520
RAYMOND F. GASSER AND D. MILLER WISE
gorilla. The stout communication that
Gasser and Hendrickx ('69) observed between the frontal and trochlear nerves during embryonic development was not evident in the adult. We observed only that
the nerves are adjacent for a considerable
distance in the proximal part of their
course (fig. 1).
According to Lacroix ('27) the lacrimal
nerve in P . cynocephalus divides into a
medial branch that supplies the lacrimal
gland, conjunctiva and eyelids and a larger
lateral branch that leaves the orbit by a
foramen in the region of the maxillo-malar
(zygomatic) junction to become subcutaneous. We observed a similar pattern (fig. 1).
Christensen ('33) indicated that in the
rhesus monkey, the lacrimal nerve gives
rise to a supraorbital nerve. This branching pattern could explain the larger lacrimal nerve reported in this animal.
The course of the nasociliary nerve
through the orbit and the branches of this
nerve appear to be similar to that found
by Christensen ('33) in the rhesus monkey.
Several infratrochlear branches that innervate the skin on the root of the nose and
an external nasal branch were found (figs.
4, 5). Raven ('50) illustrated one infratrochlear and two external nasal branches
in the gorilla.
Bowden, Mahran and Godding ('60)
made no mention of a communication between the ophthalmic division and the
facial nerve in baboons. We sometimes
found a fine nerve fascicle connecting the
zygomatic branch of the lacrimal nerve
to the facial nerve in the infraorbital region (figs. 4, 5).
Maxillary division
According to Lacroix ('27) the maxillary
division in P . cynocephalus gives rise to a
small nerve that passes through the sphenomaxillary fissure and sends branches to the
lacrimal gland. Gasser and Hendrickx
('69) reported that communications exist
between the pterygopalatine and ciliary
ganglia in baboon embryos. Our dissections revealed several orbital branches that
course from the pterygopalatine ganglion
to the orbital nerves as they pass through
the superior orbital fissure (fig. 3). Such
communications are probably the route
whereby the lacrimal gland receives its
secretomotor innervation.
The zygomatic nerve from the maxillary
division was found to have a variable
course and branching pattern (figs. 2, 4,
5). The findings of Ashton and Oxnard
('58) support this. They observed no zygomaticotemporal nerve in the orangutan and
in two of the four rhesus monkeys they
examined. In one human dissection they
reported that the zygomaticotemporal and
zygomaticofacial branches arise separately.
According to Raven ('50) each of these
branches is present in the gorilla.
The infraorbital nerve fascicles give off
two superior alveolar nerves in the infraorbital canal which travel to the rostral
maxillary teeth (fig. 3). The more lateral
nerve has been referred to as the middle
superior alveolar nerve. Fitzgerald ('56)
reported that this nerve is present in four
out of five human specimens he examined
but Ashton and Oxnard ('58) saw only an
anterior superior alveolar nerve and made
no mention of a middle branch in Circopithecoidea (rhesus, baboon and guenon).
The division terminates as five or six
large infraorbital nerve fascicles which
pass through separate foramina to innervate the skin of the lower eyelid, lateral
snout and upper lip (figs. 4, 5). The foramina exhibit some variation in their size
and location. Ashton and Oxnard ('58)
pointed out the variability in the branching
pattern of this nerve in Circopithecoidea.
They described the nerve as leaving the
skull through three infraorbital openings
that are arranged in a characteristic pattern. However, in two of the baboons they
studied, the nerve emerged through five
separate foramina. Occasionally, we found
six separate infraorbital nerves outside the
skull. They made no mention of the palpebral branch we found in the baboon but
they did observe twigs to the medial part
of the lower eyelid in the orangutan,
chimpanzee and man. In the gorilla, the
nerve emerges from the skull through a
solitary foramen (Raven, '50) as is also
the case in man.
Communications exist between the
facial and the infraorbital and zygomatic
nerves (figs. 4, 5). Gasser and Hendrickx
('67) demonstrated these communications
in 45-54 day old baboon embryos. Numer-
BABOON TRIGEMINAL NERVE
ous communications were found between
the maxillary division and the facial nerve
in all of the primate types examined by
Bclwden, Mahran and Godding ('60) which
included the baboon.
Mandibular division
The nerve to the medial pterygoid arises
from the undivided portion of the division
or' from the adjacent otic ganglion (figs.
2: 3). In addition, fascicles from the nerve
to' the mylohyoid course to the caudal portion of the medial pterygoid muscle.
Schwartz and Huelke ('63) observed that
in the rhesus monkey, the nerve to the
medial pterygoid muscle arises from the
posterior (dorsal) division. They also reported that the posterior portion is larger
than the anterior (ventral) which is also
tlhe case in the baboon. In addition, they
found that the anterior division courses
through the lateral pterygoid plate by passing through a pterygoalar foramen. Swindler ('67) and the present studies revealed
the same arrangement in the baboon.
The nerve to the mylohyoid is regularly
;Lbranch of the inferior alveolar nerve just
before the latter nerve enters the mandible
!:figs. 2, 3). Gasser and Hendrickx ('69)
observed this arrangement during early
liaboon development and Schwartz and
:Huelke ('63) described a similar origin in
the rhesus monkey. However, Christensen
('33) reported that in the rhesus, this nerve
arises as a separate branch from the
mandibular division just distal to the origin
of the auriculotemporal nerve. Swindler
('67) indicated that the nerve can separate
from the major trunk high up in the infratemporal fossa in the baboon.
Four to five mental nerves were observed
with variable size and position (figs. 2,
4, 5). Gasser and Hendrickx ('67) observed three to four mental nerve fascicles
during development with each emerging
from the mandible through separate foramina. Both Christensen ('33) and
Schwartz and Huelke ('63) described only
one mental nerve in the rhesus monkey
and the illustration of Raven ('50) shows
the same in the gorilla.
We were able to isolate the submandibular ganglion which has communications with the lingual nerve as well as the
521
nerve to the mylohyoid and sends a branch
to the mylohyoid and medial pterygoid
muscles (figs. 2, 3). Christensen ('33) observed a submaxillary (submandibular)
ganglion but Schwartz and Huelke ('63)
were unable to fmd a discrete one in the
rhesus monkey.
Communications were found between
the facial nerve (md the auriculotemporal,
buccal and mental nerves (figs. 4, 5). This
supports the finclings of Bowden, Mahran
and Godding ('60). Gasser and Hendrickx
('67) observed these communications in
45-54 day old baboon embryos. The communications rewaled by the present study
between the mental and facial nerves are
not as numerous; or as prominent as those
reported during development. Raven's ('50)
drawing depicted similar communications
between the mandibular division branches
and the facial nerve in the gorilla. Numerous prominent communications exists between the lingual and hypoglossal nerves
(fig. 3). In the rhesus monkey, Schwartz
and Huelke ('63) observed one such
communication.
ACKNOWLEDGMENTS
The authors wish to thank Dr. Andrew
G. Hendrickx and the Southwest Foundation for Research and Education, San
Antonio, Texas for supplying the embalmed specimens. Miss Cathy Chase and
Mr. Charles Falk are acknowledged for
their technical assistance.
LITERATURE CITED
Ashton, E. H., and C. E. Oxnard 1958 Some
variations in the maxillary nerve of primates.
Proc. Zool. SOC.London, 131: 457-470.
Bowden, R. E.M . , Z. Y. Mahran and M. R. Godding
1960 Communications between the
facial and trigeminal nerves in certain mammals. Proc. Zool. SOC.London, 135: 587-611.
Christensen, K. 1933 The Anatomy of the
Rhesus Monkey. Chap. XV. G . C. Hartman and
W. L. Straus, Jr., eds. Williams and Wilkins
Co., Baltimore, pp. 290-306.
Fitzgerald, M. J. T. 1956 The occurrence of the
middle superior alveolar nerve in man. Proc.
J. Anat. Londcn, 90: 586.
Gasser, R. F., and A. G. Hendrickx 1967 The
development ,of the facial nerve in baboon
embryos (Papio s p . ) . J. Comp. Neur., 129:
203-218.
522
RAYMOND F. GASSER AND D. MILLER WISE
1969 The development of the trigeminal nerve in baboon embryos (Papio sp.). J.
Comp. Neur., 136: 159-182.
Hill, W. C. 0. 1970 Comparative Anatomy and
Taxonomy. Primates. Vol. 8, Cynopithecinae
(Papio, Mandrillus, Theropithecus). WileyInterscience, New York, 200-208.
Lacroix, M.R. 1927 Considbrations sur les rapportes des nerfs lacrymal et orbitaire chez les
mammifbres supbrieurs et chez l’homme. Arch.
D’Anat. D’Hist. et D’Embry., 6: 33-64.
Raven, H. C. 1950 The Anatomy of the Gorilla.
Chap. 11. W. K. Gregory, ed. Columbia University Press, New York, pp. 15-188.
Schwartz, D. J., and D. F. Huelke 1963 Morphology of the head and neck of the macaque
monkey: the muscles of mastication and the
mandibular division of the trigeminal nerve. J.
Dent. Res., 42: 1222-1233.
Swindler, D. R. 1967 Personal Communication.
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