S9 Infratemporal Fossa - LabLink

Click here for a condensed, step-by-step dissection summary.

Locate and identify the relevant osteological features

Find these structures:

  • Sphenoid bone
    • Greater wing
      • Infratemporal surface
    • Pterygoid process
      • Lateral plate
    • Pterygomaxillary fissure
    • Foramen ovale
    • Foramen spinosum
  • Mandible
    • Ramus
      • Neck
    • Mandibular foramen
    • Temporal bone
    • Petrotympanic fissure

Examine the boundaries of the infratemporal fossa

Find these structures:

  • Maxillary vein (and pterygoid plexus)
  • Maxillary artery
    • First (mandibular) part
      • Deep auricular a.
      • Anterior tympanic a.
      • Middle meningeal a.
      • Inferior alveolar a.

1.) Review the boundaries and contents of the infratemporal fossa.

Note: The medial and lateral pterygoid mm. discussed in the previous lab are found within the infratemporal fossa, but the focus of this session is the neurovasculature of the infratemporal fossa: the maxillary a. & v. (& branches) and the mandibular n. (V3).

Note: The infratemporal fossa is a region deep to the ramus of the mandible that contains numerous structures, chiefly the: maxillary artery (& branches), the mandibular n. (& branches), and lateral and medial pterygoid mm. The infratemporal fossa is bounded:

  • superiorly by the infratemporal surfaces of both the greater wing of the sphenoid and temporal bones,
  • medially by the lateral plate of the pterygoid process (sphenoid),
  • laterally by the ramus of the mandible, and
  • anteriorly by the posterior margin of the maxilla.

There is no floor to the infratemporal fossa.

Photo 1. Infratemporal fossa

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Photo 2. Infratemporal fossa

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Note: Within the infratemporal fossa, the maxillary artery is typically superficial (lateral) to the lateral pterygoid m. Deep to the lateral pterygoid m. is the mandibular n. (V3) and its major components: the main trunk, anterior divisions, and posterior divisions.

2.) If remaining, locate the maxillary v. and pterygoid (venous) plexus.

Note: The pterygoid (venous) plexus returns blood from the infratemporal fossa and communicating areas. The pterygoid plexus communicates with the facial vein, the pharyngeal plexus, and the cavernous sinus. The pterygoid plexus coalesces into the maxillary v., which then joins the superficial temporal v. to form the retromandibular v. It is very likely that the pterygoid plexus has been removed in a previous lab, but you may notice remains of it associated with the maxillary v.

Photo 3. Maxillary v. and pterygoid plexus

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3.) On the external carotid a., find the branching point for the maxillary a., and follow the artery into the infratemporal fossa.

Note: The maxillary a. and the superficial temporal a. are the terminal branches of the external carotid a. The maxillary a. supplies the structures within the infratemporal fossa, muscles of mastication, the middle ear, and areas of the deep face with blood. The maxillary a. may be conceptually divided in three parts. The first (mandibular) part of the maxillary a. lies posterior to the lateral pterygoid m., the second (pterygoid) part lies adjacent (either superficial or deep) to the lateral pterygoid m. The third (pterygopalatine) part of the maxillary a. lies anteromedial to the lateral pterygoid m. and passes through the pterygomaxillary fissure to enter the pterygopalatine fossa. Branches of the maxillary a. will often accompany similarly named branches of the mandibular n. (V3), and may be located concurrently.

Note: The maxillary a. may take two different courses in the infratemporal fossa relative to the lateral pterygoid m. Typically, the maxillary a. runs most of its proximal course superficial (lateral) to the inferior head of the lateral pterygoid m. before diving deep to the muscle to terminate in the pterygomaxillary fissure. Another variation is the proximal maxillary a. courses deep (medial) to the lateral pterygoid m.

Photo 4. Maxillary a., first (mandibular) part

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4.) Locate the following branches of the first (mandibular) part of the maxillary a.: deep auricular a., anterior tympanic a., middle meningeal a., and inferior alveolar a.

Note: The first (mandibular) part of the maxillary a. branches from the external carotid a. deep to the neck of the mandible, and travels between the ramus and the sphenomandibular ligament. The course of the first (mandibular) part is horizontal, and all of its branches traverse bone. Some of these branches may accompany mandibular (V3) n. branches.

Note: The deep auricular a. pierces the wall of the external acoustic meatus to supply a portion of the skin of the tympanic membrane and lining of the external acoustic meatus with blood. The deep auricular a. sometimes contributes minor contributions to the TMJ.

Note: The anterior tympanic a. typically arises from the maxillary a. adjacent to the deep auricular a., then passes through the petrotympanic fissure to enter (and supply) the middle ear. The chorda tympani exits the middle ear to enter the infratemporal fossa via the petrotympanic fissure.

Photo 5. Maxillary a., first (mandibular) part

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Note: The middle meningeal a. arises from the maxillary a. and travels superiorly through the foramen spinosum to enter the cranial vault where it supplies the dura mater and most of the bones of the neurocranium. The auriculotemporal n. divides as it exits the posterior division of V3, encircles the middle meningeal a. proximally, and then the middle meningeal a. enters the foramen spinosum. The middle meningeal a. may also arise from a common trunk with the inferior alveolar a.

Note: An accessory meningeal a. may also arise from either the maxillary a., or the middle meningeal a. before ascending to (and through) the foramen ovale to enter the cranial vault.

Note: The inferior alveolar a. branches inferiorly from the maxillary a. and accompanies the inferior alveolar n. into the mandibular foramen of the mandible. The inferior alveolar a. supplies the mandible, mandibular teeth & gingiva, and the mylohyoid m.

Photo 6. Maxillary a., first (mandibular) part

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Find these structures:

  • Maxillary artery
    • Second (pterygoid) part
      • Masseteric a.
      • Posterior deep temporal a.
        • Pterygoid brs.
      • Anterior deep temporal a.
      • Buccal a.

5.) Examine the relationship of the donor’s maxillary aa. to the lateral pterygoid muscles. If the second part of the donor’s maxillary aa. run deep to the lateral pterygoid muscles, bilaterally remove the lateral pterygoid muscles. If the second part of the maxillary arteries are superficial to the lateral pterygoid muscles, find the branches of the second part on both sides, and then remove the lateral pterygoid m. of the side with the poorest examples of maxillary artery branches. Thus, you are establishing superficial and deep dissections of the infratemporal fossa.

Dissection plan for donors with second part of maxillary a. deep to lateral pterygoid m. You will not be able to further study the lateral pterygoid mm. on your donor, but this is necessary to see the details of both the maxillary a. and the mandibular n. (V3).

D1 S9 Dissection Plan (1)

Dissection plan for donors with second part of maxillary a. superficial to lateral pterygoid m.

D1 S9 Dissection Plan (2)

Photo 7. Procedural: reflected lateral pterygoid m.

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6.) Locate the branches of the second (pterygoid) part of the maxillary a., the: masseteric a., posterior deep temporal a. (& pterygoid brs), anterior deep temporal a., and the buccal a. Depending on the course of the maxillary a. (if the maxillary a. runs deep to the lateral pterygoid m.), you may need to reflect the lateral pterygoid m.

Note: The second (pterygoid) part of the maxillary a. is the continuation of the maxillary a. adjacent to the lateral pterygoid m. As the course of the maxillary a. is variable, the second part may either be superficial or deep to the lateral pterygoid m. All branches of the second part supply muscles of mastication and supporting tissues and structures.

Photo 8. Maxillary a., second (pterygoid) part

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Note: The masseteric a. accompanies the masseteric n. through the mandibular notch to serve the masseter m. The masseteric a. is relatively small and may also serve the TMJ. It is common for neurovasculature that serve muscles to also serve the joints affected by those muscles.

Note: The anterior & posterior deep temporal aa. rise from the second part of the maxillary a. between the temporalis m. and the temporal bone to serve the temporalis m., and to a lesser extent the temporal bone. The posterior deep temporal a. arises first and typically also supplies a variable number of smaller pterygoid brs. to the pterygoid mm., although the pterygoid brs. may arise from other maxillary a. branches.

Photo 9. Maxillary a., second (pterygoid) part

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Note: The buccal a. accompanies the buccal n. (of V3) into the buccal fascial space to serve the buccinator m., the buccal fat pad, and the buccal oral mucosa. The buccal a. frequently anastomosis with the facial a. (& its brs.).

Note: The third (pterygopalatine) part of the maxillary a. may be seen anteromedial to the lateral pterygoid m., but it (& its brs.) will be studied in a later lab.

Photo 10. Maxillary a., second (pterygoid) part

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Find these structures:

  • Mandibular n. (V3)
    • Branches of the trunk
      • Meningeal br.
      • Nerve to medial pterygoid
      • Nerve to tensor veli palatini
      • Nerve to tensor tympani
    • Anterior division
      • Masseteric n.
      • Deep temporal nn.
      • Buccal n.
        • Nerve to lateral pterygoid
    • Posterior division
      • Auriculotemporal n.
      • Lingual n.
      • Inferior alveolar n.
        • Nerve to mylohyoid
        • Mental n.
  • Otic ganglion
  • Chorda tympani
  • Submandibular ganglion

7.) For the deep dissection, if the lateral pterygoid m. is still present, remove the muscle in its entirety. Examine the maxillary a. to determine how much of V3 it obscures. Use your best judgment to either remove or reflect the maxillary a. to visualize V3 and its divisions.

Note: The mandibular n. (V3) is a division of the trigeminal n. (CN V) and exits the cranial cavity through the foramen ovale of the sphenoid bone into the infratemporal fossa. It consists of a main trunk, an anterior division, and a larger posterior division. V3 serves several important functions, chiefly: efferent to muscles of mastication and afferent to mandible, mandibular teeth & gingiva, and skin superficial to a portion of the temporal region. V3 is the deepest structure in the infratemporal fossa. Branches of V3 will often accompany similarly named branches of the maxillary a., and may be located concurrently.

Photo 11. Mandibular n. (V3)

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8.) Locate branches of the posterior division of the V3.

Note: The posterior division of V3 is the largest portion of the nerve. The posterior division gives rise to the following nerves:

  • auriculotemporal n.
  • inferior alveolar n.
  • lingual n.

Note: The auriculotemporal n. typically encircles the middle meningeal a., then ascends from the infratemporal fossa posterior to the TMJ. The auriculotemporal n. is part of the parasympathetic secretomotor pathway to the parotid gland (see below). The auriculotemporal n. is afferent (sensory) to the TMJ, to a portion of the skin of external acoustic meatus, to the skin of the anterior auricle of the ear, and to the skin of the superior V3 dermatome (anterior and anterosuperior to the ear).

Photo 12. Mandibular n. (V3), posterior division, auriculotemporal n.

Note: The inferior alveolar n. (IAN) typically descends posterior to the lateral pterygoid m. and gives off a small branch, the nerve to mylohyoid, near the lingula of the mandible before entering the mandibular foramen. The nerve to mylohyoid efferently (motor) serves the mylohyoid m. and the anterior belly of the digastric m. In the mandibular canal, the IAN forms the inferior dental plexus, just inferior to the apices of the mandibular teeth. The inferior dental plexus afferently (sensory) serves the mandible and mandibular teeth and gingiva. Deep to the premolars, the inferior dental plexus separates into two terminal divisions: the incisive br. (to serve the incisors) and the mental n. (to serve the skin of the chin and lower lip). The mental n. exits the mandible through the mental foramen.

Photo 13. Mandibular n. (V3), posterior division, inferior alveolar n.

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Note: The lingual n. lies anterior to the IAN for most of its course in the infratemporal fossa. The lingual n. afferently (sensory) serves the presulcal part (anterior 2/3rds, excepting vallate papillae) of the tongue and the mucosa of the floor of the oral cavity. The lingual n. is joined by the much smaller chorda tympani, a relationship that includes the lingual n. as part of the parasympathetic secretomotor pathway to the submandibular and sublingual glands, as well as taste for the presulcal part of the tongue (see below).

Note: The chorda tympani is a branch of the facial n. (CN VII) that enters the infratemporal fossa via the petrotympanic fissure. Its fibers join the lingual n. en route to the submandibular ganglion. Postganglionic fibers from the submandibular ganglion innervate the submandibular and sublingual glands. Chorda tympani also conducts special sensation (taste) from the presulcal part (anterior 2/3rds) of the tongue.

Photo 14. Mandibular n. (V3), posterior division, lingual n.

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9.) Locate branches of the anterior division of the V3.

Note: The anterior division of V3 includes three major nerves:

  • masseteric n.
  • deep temporal nn.
  • buccal n.
    • nerve to lateral pterygoid

Note: The buccal n. emerges between the heads of the lateral pterygoid m. and afferently (sensory) serves the regions adjacent to the buccinator m. (the buccal mucous membrane & posterior gingiva, and skin). The buccal n. typically gives rise to the nerve to the lateral pterygoid to serve the lateral pterygoid m. The buccal n. must not be confused with the buccal brs. of the facial n. (CN VII), although these nerves frequently anastomose. The buccal n. accompanies the buccal a. Clinicians often refer to this nerve as the long buccal n.

Note: The masseteric n. courses laterally, posterior to the tendon of the temporalis m. to serve the masseter m. and to a lesser extent the TMJ. The masseteric n. accompanies the masseteric a.

Photo 15. Mandibular n. (V3), anterior division

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Note: The deep temporal nn. are variable in number. Typically, there are two nn. (anterior and posterior) that accompany the deep temporal aa. to serve the temporal m. The posterior n. is generally larger than the anterior n. In some cases, a middle n. may be present. These nerves may arise from other brs of V3. For instance, the anterior deep temporal n. may arise from the buccal n., and the posterior deep temporal n. may arise from the masseteric n. The deep temporal nn. accompany the deep temporal aa.

Photo 16. Mandibular n. (V3), anterior division

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Note: The trunk of V3 includes four nerves:

  • meningeal br.
  • nerve to medial pterygoid
  • nerve to tensor tympani
  • nerve to tensor veli palatini

These nerves are typically very small and are difficult to locate.

Note: The meningeal br. of V3 accompanies the middle meningeal a. through the foramen spinosum, and thereafter branches to accompany brs. of the middle meningeal a. The meningeal br. afferently serve the dura mater and bones of the middle cranial fossa.

Note: The nerve to medial pterygoid is very gracile and serves the medial pterygoid m. Typically, the nerve to medial pterygoid also produces even smaller branches:

  • nerve to tensor tympani, and the
  • nerve to tensor veli palatini,

which pass from the nerve to medial pterygoid through the otic ganglion (without synapsing) to reach their namesake target muscles.

Photo 17. Mandibular n. (V3), trunk brs.

10.) With fine forceps, gently reflect the posterior trunk of V3 to reveal the otic ganglion.

Note: The otic ganglion is a parasympathetic ganglion associated in location with the deep portion of the mandibular n. (V3) trunk, just inferior to the foramen ovale. The otic ganglion receives preganglionic parasympathetic fibers from the lesser petrosal n. (glossopharyngeal n. → tympanic n. → lesser petrosal n.). Postganglionic fibers are transmitted to the parotid gland via the auriculotemporal n. (of V3).

Photo 18. Mandibular n. (V3), posterior division, otic ganglion