Anatomy of Infratemporal fossa in a Nutshell

Anatomy of Infratemporal fossa

Walls of Infratemporal fossa (not on exam)

• Infratemporal fossa is deep to zygomatic arch and ramus of mandible
• Anterior wall is the posterior maxilla
• Posterior wall is open, no clear boundary
• Superiorly, fossa extends along greater wing of sphenoid and temporal bone
• Inferiorly, is open, no clear boundary
• Laterally, find the zygomatic arch
• Medially, the lateral pterygoid plate

Contents of infratemporal fossa:

• Parts of the muscles of mastication (not all of muscles)
• Maxillary artery (plus 10 of its 17 branches)
• Pterygoid plexus of veins
• Branches of mandibular division of trigeminal nerve

Muscles of mastication: all innervated by third division of Trigeminal nerve (mandibular division)

• Actions:
  • Protrusion of the mandible:

1. 1. • Go forward, stick out chin.
      • Is for grinding teeth- requires alternation of motion between retraction / protrusion.

1. • Retraction of the mandible: opposite of protrusion
   • Depress the mandible:

1. 1. • Open mouth
      • Suprahyoid muscles aid in depression

• • • Gravity is responsible as well

• • Elevate the mandible: close mouth
• Temporalis muscle:
  • Origin: Temporal lines (both superior / inferior)
  • Inserts: Coronoid process / anterior margin of the ramus of the mandible.
  • Runs deep to zygomatic arch, thus found both in temporal and infratemporal regions
  • Action: Retraction, Elevation
• Masseter:
  • 2 heads (superficial / deep)
  • Origin: Superficial / Deep aspect of zygomatic arch
  • Inserts: on the lateral (external) surface of the ramus of the mandible (ramus OTM) (from coronoid process to the angle of the mandible)
  • Action: protraction, elevation
• Medial Pterygoid:
  • 2 heads
  • Origin: from medial surface of the lateral pterygoid plate and from adjacent portion of maxilla
  • Insert: on the internal aspect of the ramus of the mandible similar to masseter (from coronoid process to the angle)
  • Action: protraction, elevation
  • Along with the masseter, the medial pterygoid forms a sling for the mandible at the angle OTM which acts to hold it to the skull.
• Lateral Pterygoid:
  • Deepest of the muscles
  • 2 heads
  • Origin: (common) lateral surface of the lateral pterygoid plate and the adjacent portion of the sphenoid bone
  • Insert:

1. 1. • 1^st head attaches to the mandibular head
      • 2^nd head attaches articular disk inside the TMJ

• • • Action: major protractor, minor depressor

Maxillary artery:

• Larger of the two terminal branches of external carotid
• Supplies muscles of mastication
• External carotid passes posterior to mandibular head where the maxillary artery is given off (and external carotid becomes superficial temporal artery)
  • It then enters the infratemporal fossa deep (posterior) to the mandibular head (enters fossa superficial to lateral pterygoid muscle)
  • Exits the fossa to enter the nasal cavity
• Have 3 parts
  • 2 are in the infratemporal fossa
  • 1 is in the nasal cavity (is where it terminates)
• Has 17 branches, 10 are in infratemporal fossa- 4 are important:
  • Middle meningeal artery

1. 1. • Given off deep in infratemporal fossa (see short part of it)
      • Goes through foramen spinosum à enters middle cranial fossa to take epidural position to supply the dura mater.

• • • Sometimes have an accessory meningeal artery which has the exact same function (supply dura mater) but traverses through Foramen Ovale (where mandibular nerve is entering)

1. • Inferior alveolar artery

1. 1. • Enters the mandibular canal
      • Gives off blood supply to lower teeth

• • • Exits canal via mental foramen and thus becomes mental artery→ goes on to supply skin of the chin.

1. 1. Deep temporal arteries

1. 1. • Arteries to the temporalis muscle
      • Travel superiorly (2 or more)

1. 1. Posterior superior alveolar artery

1. 1. • Supplies the teeth of the upper jaw
      • Maxilla lacks canal, thus this artery goes into posterior aspect of the maxilla

• • • Sometimes, this artery is more given off from the nasal cavity

• Potential Paths of maxillary artery:
  • Normal pathway: (most)

1. 1. • Maxillary artery is on superficial side of the lateral pterygoid muscle.
      • Middle meningeal artery goes behind the muscle

1. • Aberrant pathway:

1. 1. • Maxillary artery goes deep to lateral pterygoid
      • Middle meningeal artery is still deep

• • • May confuse deep temporal artery as being maxillary

 Pterygoid plexus of veins

• Between temporalis muscle (superficial) and the pterygoid muscles.
• Receives blood from
  • The muscles of mastication
  • The superficial face (facial vein)
  • The orbits
  • The cavernous sinus
  • From the pharynx
• This plexus coalesces to form 1 or 2 maxillary veins which joint superficial temporal vein
• This will be in the area of the maxillary artery. Has an appearance of fascia due to dense network.

Nerves of infratemporal fossa

• Mandibular division of the Trigeminal nerve has many branches
• Nerve has 2 components
  • Motor component: to skeletal muscles derived from 1^st pharyngeal arch
  • Sensory component: to skin of the chin/cheek/temple, lower teeth, innervation to lower teeth, gums, tongue.
• Enters into infratemporal fossa using the Foramen Ovale
• Motor Branches:
  • Muscular branches: for mastication

1. 1. • To temporalis
      • To masseter
      • To medial pterygoid

• • • To lateral pterygoid

1. • Muscular branches: tensors

1. 1. • To Tensor Veli Palatini– a muscle of the soft palate
      • To Tensor Tympani (tympanic membrane of middle ear)

1. • Nerve to mylohydoid supplies:

1. 1. • Mylohyoid muscle
      • Anterior belly of Digastric muscle (posterior belly is by facial nerve)

• Sensory Branches:
  • Auriculotemporal nerve:

1. 1. • Supplies skin of anterior ear and temple
      • In infratemporal fossa, it normally encircles the middle meningeal artery (splits to go around it)
      • When it leaves the fossa, it travels with the superficial temporal artery anterior to ear / on temple.

1. • Inferior Alveolar nerve:

1. 1. • Supplies lower teeth→enters mandibular foramen
      • Becomes mental nerve when exits the mental foramen to supply skin of chin and lower jaw

1. • Lingual nerve:

1. 1. • Supplies the anterior 2/3 of the tongue
      • Note: this is general sensation for pain, touch, temperature

1. 1. Buccal nerve:

1. 1. • Supplies skin of the cheek
      • Pierces the buccinator muscle and supplies mucous membrane on the inside of the cheek

• Other structures in Fossa
  • Otic Ganglion

1. 1. • Parasympathetic ganglion
      • Preganglionic neuron is a branch of the Glossopharyngeal nerve (CN IX) and is called the Lesser Petrosal nerve.

• • • Lesser petrosal nerve synapses in Otic Ganglion with postganglionic fibers→go to Parotid gland (is the effector)

• • • The Auriculotemporal nerve is a branch of the mandibular nerve (third division of Trigeminal) is going along the same path:
      1. Goes through the parotid to supply target skin.
      2. Post ganglionic fibers are in the same fascial sheath as the auriculotemporal nerve until reach the parotid gland.
    • A patient with a lesion of the trigeminal nerve will have a fully functional parotid gland (because it is not innervated by it, it only supplies a means of travel for the post ganglionic fibers).
    • This ganglion is suspended from the trigeminal nerve, but is not a part of it.

1. • Chorda Tympani

• • • Note: the Lingual nerve is a branch of the trigeminal nerve V3 which supplies anterior 2/3 of the tongue.
    • Chorda Tympani is a branch of facial nerve, it goes through the tongue to end in taste buds in the tongue.
      1. Carries taste sensation for anterior 2/3 of the tongue
      2. hitches a ride with the lingual nerve to the anterior 2/3 of the tongue where it leaves to go to the taste buds.

• • • Chorda Tympani and Lingual nerve are tightly bound together in the tongue: lesions in 3 areas have different effects
      1. Lesion in facial nerve = loss of taste
      2. Lesion in Lingual = loss of touch
      3. Lesion in lingual nerve after synapse = loss of both.

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