The pterygoid canal (Fig. 8.154A) is a bony canal running horizontally through the root of the pterygoid process of the sphenoid bone. It opens anteriorly into the pterygopalatine fossa. Posteriorly it continues through the cartilage filling the foramen lacerum and opens into the middle cranial fossa just anteroinferior to the internal carotid artery as the vessel enters the cranial cavity through the carotid canal (Fig. 8.154B).
Seven foramina and fissures provide apertures through which structures enter and leave the pterygopalatine fossa (Fig. 8.155):
The foramen rotundum and pterygoid canal communicate with the middle cranial fossa and open onto the posterior wall.
A small palatovaginal canal opens onto the posterior wall and leads to the nasopharynx.
The palatine canal leads to the roof of the oral cavity (hard palate) and opens inferiorly.
The sphenopalatine foramen opens onto the lateral wall of the nasal cavity and is in the medial wall.
The lateral aspect of the pterygopalatine fossa is continuous with the infratemporal fossa via a large gap (the pterygomaxillary fissure) between the posterior surface of the maxilla and pterygoid process of the sphenoid bone.
The superior aspect of the anterior wall of the fossa opens into the floor of the orbit via the inferior orbital fissure.
The maxillary nerve [V2] and terminal part of the maxillary artery enter and branch within the pterygopalatine fossa. In addition, the nerve of the pterygoid canal enters the fossa carrying: preganglionic parasympathetic fibers from the greater petrosal branch of the facial nerve [VII], and postganglionic sympathetic fibers from the deep petrosal branch of the carotid plexus.
The preganglionic parasympathetic fibers synapse in the pterygopalatine ganglion and both the sympathetic and postganglionic parasympathetic fibers pass with branches of the maxillary nerve [V2] out of the fossa and into adjacent regions.
In addition to nerves and arteries, veins and lymphatics also pass through the pterygopalatine fossa.
The maxillary nerve [V2] is purely sensory. It originates from the trigeminal ganglion in the cranial cavity, exits the middle cranial fossa, and enters the pterygopalatine fossa through the foramen rotundum (Fig. 8.156). It passes anteriorly through the fossa and exits as the infra-orbital nerve through the inferior orbital fissure.
While passing through the pterygopalatine fossa, the maxillary nerve [V2] gives rise to the zygomatic nerve, the posterior superior alveolar nerve, and two ganglionic branches (Fig. 8.156). The two ganglionic branches originate from its inferior surface and pass through the pterygopalatine ganglion.
Postganglionic parasympathetic fibers, arising in the pterygopalatine ganglion, join the general sensory branches of the maxillary nerve [V2] in the pterygopalatine ganglion, as do postganglionic sympathetic fibers from the carotid plexus. The three types of fibers leave the ganglion as orbital, palatine, nasal, and pharyngeal branches.
Orbital branches. The orbital branches are small and pass through the inferior orbital fissure to contribute to the supply of the orbital wall and of the sphenoidal and ethmoidal sinuses.
Greater and lesser palatine nerves. The greater and lesser palatine nerves (Fig. 8.156) pass inferiorly from the pterygopalatine ganglion, enter and pass through the palatine canal, and enter the oral surface of the palate through the greater and lesser palatine foramina.