S9 Infratemporal Fossa - Learning Objectives
1. What bony opening(s) do fibers of V3 exit from the skull?
The large sensory root of the mandibular n. (V3) emerges from the lateral part of the trigeminal ganglion and exits the skull via the foramen ovale. The small motor root passes under the ganglion and through the foramen ovale to unite with the sensory root just inferior to the skull.
Mandibular n. immediately passes between tensor veli palatini m. (medial) and the lateral pterygoid m. (lateral), and gives off a meningeal branch and several motor branches. The nerve then divides into a small anterior and large posterior trunk.
2. What bony structures & landmarks delineate the temporal fossa and infratemporal fossa?
A lateral view of the temporal region can be divided into 2 main parts: temporal fossa (superior) & infratemporal fossa (inferior). These fossae are demarcated by the zygomatic arch, and are continuous with one another.
- Medial: frontal, parietal, temporal, and sphenoid bones
- Pterion: junction of these 4 bones; middle meningeal a., anterior branch typically lies deep to pterion
- Lateral: temporal fascia
- Anterior: posterior surface of frontal process of zygomatic & posterior surface of the zygomatic process of frontal
- Superior: superior and inferior temporal lines
- Inferior: zygomatic arch (laterally) & infratemporal crest of greater wing of sphenoid (medially)
- Temporalis m.
- Deep temporal aa. & nn.
- Superficial temporal a.
- Zygomaticotemporal n.
The infratemporal fossa can be visualized as having a wedge shape. It is located deep to the masseter muscle and zygomatic arch (to which the masseter attaches).
The infratemporal fossa communicates with:
- Temporal fossa (superiorly)
- Pterygopalatine fossa (medially) through the pterygomaxillary fissure
- Orbit (anteriorly) through inferior orbital fissue
- Middle cranial fossa through foramen ovale and spinosum
- Lateral: Ramus of mandible
- Medial: Lateral pterygoid plate of sphenoid
- Anterior: Posterior surface of maxilla
- Posterior: Mastoid & styloid processes and tympanic plate of temporal bone
- Inferior: Medial pterygoid m. at attachment site (angle of mandible)
- Superior (roof): Greater wing of sphenoid
- Distal end of temporalis m.
- Pterygoid mm.
- Maxillary a.
- Pterygoid venous plexus
- Nervous tissue:
- Otic ganglion
- Mandibular n. (V3) & branches
- Chorda tympani
3. What muscles comprise the masticatory (pterygomasseteric) sling?
The masseter and medial pterygoid are associated as a sling (“masticatory sling”) and for the most part they pull in an upward (elevation) and forward (protrusion) direction.
4. What are the three divisions of the maxillary artery?
The maxillary a. is one of the two terminal divisions of the external carotid a., and distributes blood flow to the upper maxilla and lower mandible, deep facial areas, the middle ear, cerebral dura mater, and the nasal cavity. It is considered a blood vessel which supports both hard and soft tissue in the maxillofacial region.
The main trunk of the maxillary a. is divided into three parts, which are named according to related structures along the artery’s course (path of travel).
5. What are the divisions of the mandibular n. (V3)?
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, and 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 will often accompany similarly named branches of the maxillary a., and may be located concurrently.
From the main trunk (proximal to the divisions):
- Muscular branches (motor)
- Nerve to medial pterygoid
- Nerve to tensor tympani
- Nerve to tensor veli palatini
- Meningeal br. (sensory)
From the anterior division:
- Massetetic n. (motor)
- Deep temporal nn., anterior & posterior (motor)
- Nerve to lateral pterygoid (motor)
- (Long) buccal n. (sensory)
From the posterior division:
- Auriculotemporal n. (sensory)
- Lingual n. (sensory)
- Inferior alveolar n. (both)
- Nerve to mylohyoid (motor) - before entering mandibular foramen
6. Describe the pterygoid plexus of veins (what areas does the plexus drain? with which veins does the plexus communicate?).
The pterygoid (venous) plexus returns blood from the infratemporal fossa and communicating areas. The pterygoid plexus communicates with the facial v., 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.
7. What are the pterygoid plates, which muscles attach here, and what function does the pterygoid hamulus serve?
Functionally, the medial pterygoid plate is related to the pharyngeal region, and the lateral pterygoid plate is related to the infratemporal fossa.
The lateral pterygoid plate is a thin plate of bone, which forms the lateral part of a horseshoe-like process that extends from the inferior aspect of the sphenoid bone.
Lateral surface of lateral pterygoid plate:
- Attachment of lateral pterygoid m.
- Forms medial wall of infratemporal fossa
Medial surface of lateral pterygoid plate:
- Attachment of medial pterygoid m.
- Forms part of pterygoid fossa
The medial pterygoid plate is comparably longer than the lateral pterygoid plate, and has a distinctive process (the pterygoid hamulus) which extends inferolaterally. This plate of bone serves as an attachment point for the pterygomandibular raphe (the condensation of the pharyngobasilar fascia) and the superior pharyngeal constrictor m.
The pterygoid hamulus is a hook-like process at the lower aspect of the medial pterygoid plate. The tendon of the tensor veli palatini m. glides around the hamulus, and it serves as the superior attachment of the pterygomandibular raphe.
8. What nerve fibers relay taste (special sensory) and general sensory information from the tongue to the brain?
Afferently, the tongue has both general somatic and special visceral (taste) afferent innervations. An important landmark for the afferent innervation of the tongue are the vallate papilla (not the terminal sulci). In terms of somatic afferents:
- areas anterior to the vallate papillae are innervated by the lingual n. (V3), whereas
- areas posterior to the vallate papillae are innervated by the glossopharyngeal n.
There is a slight overlap of somatic afferent innervation in the posteromedial root of the tongue, which is innervated by both the glossopharyngeal n. and vagus n (via the internal br. of the superior laryngeal n.). The vallate papillae also demarcate the two sources of special visceral afferent (taste) serving the taste buds:
- anterior to the vallate papillae, taste is modulated via the facial n. (chorda tympani ← lingual n.), whereas
- posterior to the vallate papillae, taste is modulated via the glossopharyngeal n.