Pterygopalatine Fossa Anatomy
The pterygopalatine fossa lies between
the pterygoid process of the sphenoid bone posteriorly, the palatine bone
medially and the maxilla anteriorly (Fig. 7.43). It is
slit-like and opens laterally through the pterygomaxillary fissure into
the infratemporal fossa.
It contains part of the maxillary (V2) division of the
trigeminal nerve, the pterygopalatine ganglion and its branches and the
termination of the maxillary artery, together with accompanying veins and
lymphatics. The pterygopalatine fossa communicates with the middle cranial fossa
through the foramen rotundum, with the foramen lacerum through the pterygoid
canal, with the orbit through the inferior orbital fissure, with the walls of
the nasal cavity through the sphenopalatine foramen and with the palate via the
greater and lesser palatine canals.
Maxillary
(V2) division of the trigeminal nerve
The
maxillary division (Fig. 7.44) leaves
the cranial cavity through the foramen rotun- dum, crosses the pterygopalatine
fossa and continues forwards through the inferior orbital fissure into the
orbit. It terminates as the infraorbital nerve, which traverses the
infraorbital canal to reach the face. The maxillary division has several
branches arising in the pterygopalatine fossa and the floor of the orbit. In
the pterygopalatine fossa (Fig. 7.45), two branches suspend the pterygopalatine
ganglion from the parent nerve. Also arising in the fossa are the posterior superior
alveolar nerves (Figs 7.44 & 7.45), which descend in the posterior wall of the
maxillary air sinus to reach the upper molar teeth. In the floor of the orbit,
the middle and anterior superior alveolar nerves (Fig. 7.44) arise
and descend in the lateral and anterior walls of the maxilla. Collectively, the
superior alveolar nerves supply the
maxilla and its air sinus, the alveolar ridge and all the upper teeth. The zygomatic
nerve (Fig. 7.44) also arises in the floor of the orbit and ascends on the
lateral wall, dividing into zygomaticotemporal and zygomaticofacial nerves.
These branches pierce the zygomatic bone to supply the overlying facial skin. A
branch from the zygomaticotemporal nerve conveys postganglionic parasympathetic
fibres from the pterygopalatine ganglion to the lacrimal gland. The
infraorbital nerve (Fig. 7.44) emerges onto the face through the infraorbital
foramen and supplies the skin of the cheek, lower eyelid, upper lip and lateral
surface of the external nose.
Pterygopalatine
ganglion
The
pterygopalatine ganglion (Fig. 7.45) is
suspended from the maxillary division in the pterygopalatine fossa and
transmits sensory, parasympathetic and sympathetic nerve fibres. Sensory fibres
originating in the palate, nose and nasopharynx pass through the ganglion
without synapsing to enter the maxillary division. Preganglionic
parasympathetic fibres destined for the ganglion leave the brain in the facial
(VII) nerve and travel via the greater petrosal nerve. These fibres emerge from
the petrous temporal bone and pass along the floor of the middle cranial fossa
to enter the foramen lacerum, where they accompany postganglionic vasomotor sympathetic
fibres from the carotid plexus as the nerve of the pterygoid canal to reach the
pterygopalatine ganglion. In the ganglion the parasympathetic fibres synapse,
and postganglionic fibres are distributed through the appropriate branches of
the ganglion to the mucous glands in the nose and palate. Secretomotor
parasympathetic fibres destined for the lacrimal gland enter the maxillary
division and travel in its zygomatic branch. The ganglion earns its nickname,
the ‘hay fever ganglion’, by virtue of its parasympathetic component.
Sympathetic fibres are also distributed in the branches of the ganglion.
There
are five groups of branches from the pterygopalatine ganglion (Fig. 7.45): posterior lateral nasal, pharyngeal, nasopalatine,
and greater and lesser palatine. Posterior lateral nasal nerves, entering via
the sphenopalatine foramen, supply the lateral wall of the nasal cavity. The
pharyngeal branch innervates the nasopharynx. The nasopalatine nerve (Fig. 7.46) crosses the anterior surface of the body of
the sphenoid bone to enter the nasal septum, then angles
anteroinferiorly in a groove on the upper edge of the vomer, eventually passing
through the incisive canal onto the lower surface of the anterior part of the
hard palate. The nerve conveys sensation from the front of the palate and the
inferior part of the nasal septum. The greater and lesser palatine nerves
traverse the palatine canal to emerge from the appropriate palatine foramina on
the lower surface of the hard palate. The greater palatine nerve supplies the
hard palate, while the lesser innervates the soft palate.
Vessels
The
maxillary artery (Figs 7.44 & 7.45) enters the pterygopalatine fossa from
the infratemporal fossa and divides into its terminal branches which accompany
the branches of the ganglion and bear corresponding names. Venous blood drains
into the pterygoid plexus, which continues into the infratemporal fossa and
communicates with the cavernous sinus via the inferior and superior orbital
fissures.
