The anterior superior alveolar nerve also gives origin to a small nasal branch, which passes medially through the lateral wall of the nasal cavity to supply parts of the areas of the nasal floor and walls.
The infra-orbital nerve exits the infra-orbital canal through the infra-orbital foramen inferior to the orbital margin and divides into nasal, palpebral, and superior labial branches:
Nasal branches supply skin over the lateral aspect of the external nose and part of the nasal septum.
Palpebral branches supply skin of the lower eyelid.
Superior labial branches supply skin over the cheek and upper lip, and the related oral mucosa.
Nerve of the pterygoid canal and the pterygopalatine ganglion
The nerve of the pterygoid canal (Fig. 8.157) is formed in the middle cranial fossa by the union of: the greater petrosal nerve (a branch of the facial nerve [VII]), and the deep petrosal nerve (a branch of the internal carotid plexus).
The nerve of the pterygoid canal passes into the pterygopalatine fossa and joins the pterygopalatine ganglion. It carries mainly preganglionic parasympathetic and postganglionic sympathetic fibers.
The greater petrosal nerve, which originates from the geniculate ganglion of the facial nerve [VII] in the temporal bone, exits the temporal bone through a small canal that opens via a fissure onto the anterior surface of the petrous part of the temporal bone. It passes anteromedially along the posterior margin of the middle cranial fossa and then under the internal carotid artery to reach the superior surface of the cartilage filling the foramen lacerum.
As the greater petrosal nerve passes under the internal carotid artery, it is joined by the deep petrosal nerve to form the nerve of the pterygoid canal.
The greater petrosal nerve carries parasympathetic innervation to all glands above the oral fissure, including: mucous glands in the nasal cavity, salivary glands in the upper half of the oral cavity, and the lacrimal gland in the orbit.
The greater petrosal nerve also carries some taste (SA) fibers from the soft palate in the lesser palatine nerve.
The deep petrosal nerve is formed by postganglionic sympathetic fibers that originate in the superior cervical sympathetic ganglion in the neck and leave the ganglion as the internal carotid nerve.
Preganglionic fibers that synapse in the ganglion are from the T1 spinal nerve.
The internal carotid nerve forms the internal carotid plexus around the internal carotid artery as the internal carotid artery passes through the skull and into the cranial cavity. Some of the fibers from the internal carotid plexus converge to form the deep petrosal nerve, which leaves the internal carotid plexus in the middle cranial fossa and joins the greater petrosal branch of the facial nerve [VII].
The deep petrosal nerve carries postganglionic sympathetic fibers destined mainly for blood vessels.
The nerve of the pterygoid canal enters the superior surface of the cartilage that fills the foramen lacerum and passes anteriorly through the cartilage to enter the pterygoid canal in the root of the pterygoid process of the sphenoid bone. It passes through the canal and into the pterygopalatine fossa where it joins the pterygopalatine ganglion formed around the branches of the maxillary nerve [V2] (Fig. 8.157).
The pterygopalatine ganglion is the largest of the four parasympathetic ganglia in the head and is formed by the cell bodies of the postganglionic neurons associated with preganglionic parasympathetic fibers of the facial nerve [VII] carried by the greater petrosal nerve and the nerve of the pterygoid canal.