DISSECTION 8
The Infratemporal Region
References: M1 916-928, 951-955; N 13-14, 42, 50-51; N15-16, 46, 54-55; R 65, 79-83
AT THE END OF THIS LABORATORY PERIOD YOU WILL BE RESPONSIBLE FOR THE
IDENTIFICATION AND DEMONSTRATION OF THE STRUCTURES LISTED BELOW:
1. Bones and bony features: Mandible (ramus, body, coronoid process, condyloid process, head,
neck, mandibular notch, mandibular foramen, lingula); temporal bone (mandibular fossa, articular
tubercle, infratemporal crest, zygomatic process, carotid canal, stylomastoid foramen); sphenoid
bone (greater wing, lateral pterygoid plate, medial pterygoid plate, pterygoid fossa, foramen ovale,
foramen spinosum, hamulus); inferior orbital fissure, and the pterygopalatine fossa.
2. Joints: Temporomandibular joint (articular disc and two synovial cavities).
3. Muscles: Masseter, temporalis, lateral pterygoid, medial pterygoid (muscles of mastication).
4. Nerves: Inferior alveolar, lingual, auriculotemporal, chorda tympani, mylohyoid.
5. Vessels: External carotid, superficial temporal, maxillary, inferior alveolar, middle meningeal,
infraorbital, posterior superior alveolar, sphenopalatine, and the descending palatine arteries.
YOU SHOULD ALSO BE ABLE TO DO THE FOLLOWING THINGS:
1. Draw and label a diagram of the temporomandibular joint.
2. Name the muscles of mastication, give their nerve supply, and state their actions.
3. List the movements of the mandible and tell which muscles produce each movement.
4. List the types of nerve fibers found in each branch of the mandibular division of the trigeminal nerve
and give the location of their cell bodies.
5. List the types and sources of the nerve fibers in the chorda tympani nerve.
6. State the distribution and be able to label a diagram of the maxillary artery and its branches.
Before beginning the dissection, identify on a
skull the bones and bony features listed above.
Then, clean the lateral surface of the MASSETER
MUSCLE and define its borders (A731; G7.46;
N50; N54). The parotid duct may be cut and
pulled out of the way. Use a saw to divide the
zygomatic arch just in front of and just behind the
masseter muscle as in Figure 1 on the next page.
Pull the masseter and the attached zygomatic arch
outward and downward after cutting the nerve and
blood supply to the muscle. The masseter is one
of the four muscles of mastication, all of which
are innervated by branches of the mandibular
division of the trigeminal nerve. Where are the
cell bodies of the efferent fibers to these muscles
located? Strip the masseter from the surface of
the RAMUS OF THE MANDIBLE, leaving it
attached only to the angle and inferior border of
the mandible.
Dissection 8, The Infratemporal Region
Figure 1
Next, use a saw to make a parasagittal cut
through the TEMPOROMANDIBULAR JOINT.
Identify the ARTICULAR DISC and the TWO
SYNOVIAL CAVITIES (A738, 742; G7.51A; N14;
N16).
Three additional saw cuts will now be made
in the mandible, as indicated in Figure 2.
Figure 2
First, the CORONOID PROCESS will be
detached by making a saw cut from the deepest
part of the MANDIBULAR NOTCH to the superior
part of the BODY OF THE MANDIBLE (Cut #1 in
drawing). Pull the coronoid process and the
TEMPORALIS MUSCLE upward, taking note of the
nerve supply to the temporalis. Then make a
horizontal saw cut through the NECK OF THE
MANDIBLE (Cut #2 in drawing). The third saw
cut (Cut #3 in drawing) requires great care or the
inferior alveolar vessels and nerve will be cut. It
is made just above the MANDIBULAR FORAMEN,
which is located by placing a probe or scalpel
Page 2
handle deep to the remaining portion of the ramus
of the mandible and pushing it inferiorly until it is
stopped by the inferior alveolar nerve and vessels
entering the mandibular foramen. Leave the
probe or scalpel handle in this position to protect
these structures and make a saw cut across the
mandibular ramus at the same level. Be very
careful or you will cut the inferior alveolar
vessels and nerve. After removing the detached
part of the ramus, identify the INFERIOR
ALVEOLAR NERVE and ARTERY (A746, 749;
G7.10A; N65, 67, 125; N69, 71, 131). You may
be able to identify the MYLOHYOID NERVE,
which is a posterior branch of the inferior alveolar
nerve that comes off just above the mandibular
foramen (A750, 751, G7.47A; N67; N71). Just
anterior to the inferior alveolar nerve, identify the
LINGUAL NERVE (N67; N71). Clean the inferior
alveolar and lingual nerves proximally until they
pass beneath the inferior border of the LATERAL
PTERYGOID MUSCLE (N51; N55). Move the
HEAD OF THE MANDIBLE and articular disc
anteriorly and posteriorly, noting the effect of
these movements on the lateral pterygoid.
Identify the MEDIAL PTERYGOID MUSCLE (N51,
67; N55, 71), across the surface of which the
inferior alveolar and lingual nerves pass.
Cut the head of the mandible and the articular
disc free from the capsule of the
temporomandibular joint. Then carefully detach
the lateral pterygoid muscle from its origin and
remove it along with the head of the mandible and
the articular disc to which it should still be
attached. The MAXILLARY ARTERY and its major
branches, as well as the remaining branches of the
mandibular division of the trigeminal nerve may
now be identified. In particular, identify the
MIDDLE MENINGEAL ARTERY and trace it to the
base of the skull (A751; G7.47B; N65; N69).
Through what foramen does the middle meningeal
artery enter the cranial cavity? As you clean the
middle meningeal artery, look for the
AURICULOTEMPORAL NERVE, which arises from
the mandibular division by two roots passing on
either side of the middle meningeal artery. This
relationship is a useful clue to the identification of
either the artery or the nerve.
The
Dissection 8, The Infratemporal Region
Page 3
auriculotemporal nerve is a cutaneous branch of
Again, identify the LINGUAL NERVE and trace
the mandibular division of the trigeminal nerve,
it proximally until it is joined by the CHORDA
supplying the skin anterior and superior to the
TYMPANI NERVE (A751, 834, 835; G7.47A, p806,
external ear. What other cutaneous branch of the
p812; N67; N71). You should learn from what
mandibular division have you already identified
nerve the chorda tympani branches and what
in the dissection of the face? Identify the
types of fibers it contains. (See M1 Fig. 7-74,
INFRAORBITAL ARTERY and the POSTERIOR
Fig. 7.91 and p 943 and N117; N123.)
SUPERIOR ALVEOLAR ARTERY. Deep within the
PTERYGOPALATINE FOSSA look for the origins of
Follow the MAXILLARY ARTERY back to its
the SPHENOPALATINE ARTERY and the
origin from the EXTERNAL CAROTID, and identify
DESCENDING PALATINE ARTERY (A750, 751;
the beginning of the SUPERFICIAL TEMPORAL
G7.48; N65; N69). Note that the origins of these
ARTERY (A746, 749-751; G7.47A; N65; N69).
last two arteries maybe better visualized in the
What cutaneous nerve accompanies the
next dissection. Know in general terms the
superficial temporal artery?
distribution of the branches of the maxillary
artery.
_____________________________________________________________________________________
STUDY QUESTIONS
1. Draw and label a diagram showing
the essential features of the
temporomandibular joint.
Note: Dark regions above and below the articular disk
indicate the upper and lower synovial cavities.
2. Name the muscles of mastication.
2. The temporalis, the masseter, the lateral pterygoid,
the medial pterygoid.
3. What is the nerve supply to the
muscles of mastication?
3. The muscles of mastication are innervated by
branches from the mandibular division of the
trigeminal nerve.
Dissection 8, The Infratemporal Region
Page 4
4. Locate the cell bodies of the nerve
fibers in any muscular branch of
the mandibular division.
4. Motor nucleus of the trigeminal nerve.
Mesencephalic nucleus of the trigeminal nerve.
5. What muscle or muscles
5.
a) elevate the mandible?
a)
the masseter, the temporalis, and the
medial pterygoid
b) depress the mandible?
b)
the lateral pterygoid (along with the
suprahyoid muscles, particularly the digastric)
c) protract the mandible?
c)
the lateral pterygoid
d) retract the mandible?
d)
the posterior fibers of the temporalis
e) deviate the mandible to the left?
e)
the right lateral pterygoid (also the right
medial pterygoid)
6. What are the names of the cutaneous
branches of the mandibular division
that you have studied?
6. The mental nerve and the auriculotemporal nerve.
7
7. In the trigeminal (semilunar) ganglion.
Where are the cell bodies of the
afferent fibers in the cutaneous
branches of the mandibular division?
8. Are there other cutaneous branches
of the mandibular division that you
have not been asked to identify?
8. Yes. The buccal branch of the mandibular division
supplies the skin of the cheek and the mucous
membrane lining the cheek.
9. Does the buccal branch of the
trigeminal nerve supply the buccinator
muscle?
9. No, the buccinator, like the other muscles of facial
expression, is supplied by the facial nerve.
10. List all the types of nerve fibers
found in the lingual nerve distal
to its union with the chorda
tympani and for each type give
the location of its cell bodies.
10. Type of Fiber
Afferent
Afferent (taste)
Preganglionic
efferent
Location of Cell Body
Trigeminal ganglion
Geniculate ganglion
Superior salivatory nucleus
11. List the types of nerve fibers
found in the chorda tympani
nerve and give the locations
of their cell bodies.
11. Type of Fiber
Afferent (taste)
Preganglionic
efferent
Location of Cell Body
Geniculate ganglion
Superior salivatory nucleus
12. Where do the preganglionic fibers in the
chorda tympani nerve terminate?
12. In the submandibular ganglion.
Dissection 8, The Infratemporal Region
Page 5
13. Where do the postganglionic
fibers that arise from cells in
the submandibular ganglion
terminate?
13. Postganglionic fibers from the submandibular
ganglion supply the submandibular and sublingual
salivary glands.
14. Where do the afferent fibers
which the lingual nerve receives
from the chorda tympani nerve
terminate peripherally?
14
15. If the submandibular ganglion
supplies the submandibular and
sublingual salivary glands with
post-ganglionic fibers, then how
is the parotid gland supplied with
secretory fibers?
15. The parotid gland receives post-ganglionic efferent
fibers from the otic ganglion, which is located very
close to the mandibular division of the trigeminal
nerve just below the base of the skull. These
postganglionic fibers travel through the
auriculotemporal nerve to reach the parotid gland.
16. Locate the cell bodies of the
preganglionic efferent fibers
which synapse in the otic ganglion.
In which cranial nerve do these
fibers leave the brain?
16. The preganglionic efferent fibers which supply the
otic ganglion arise in the inferior salivatory nucleus
and leave the brain through the glossopharyngeal
nerve.
17. What does the mylohyoid
nerve supply?
17. The mylohyoid nerve supplies two muscles: the
mylohyoid and the anterior belly of the digastric.
These fibers are afferent for taste, and they terminate
in taste buds on the anterior 2/3 of the tongue.
18. What nerve or nerves are most subject to injury during the removal of an impacted mandibular third molar?
19. What anatomical landmarks are used in injecting local anesthetic preparatory to working on the lower teeth?
What nerve or nerves are anesthetized and what are the resulting regions of anesthesia?
20. What is the significance of the pterygoid plexus?
Dissection 8, The Infratemporal Region
21. Label as indicated:
Page 6
21. a. Superficial temporal artery
b. Deep temporal artery
c. Infraorbital artery
d. Middle meningeal artery
e. Maxillary artery
f. External carotid artery
g. Inferior alveolar artery
LJ:bh
revised
06/18/09