Pterygopalatine ganglion

The pterygopalatine ganglion (or sphenopalatine ganglion) is a parasympathetic ganglion found in the pterygopalatine fossa.

Structure
The pterygopalatine ganglion (of Meckel), the largest of the parasympathetic ganglia associated with the branches of the trigeminal nerve, is deeply placed in the pterygopalatine fossa, close to the sphenopalatine foramen. It is triangular or heart-shaped, of a reddish-gray color, and is situated just below the maxillary nerve as it crosses the fossa.

The pterygopalatine ganglion supplies the lacrimal gland, paranasal sinuses, glands of the mucosa of the nasal cavity and pharynx, the gingiva, and the mucous membrane and glands of the hard palate. It communicates anteriorly with the nasopalatine nerve.

Roots
It receives a sensory, a motor, and a sympathetic root.

Sensory root
Its sensory root is derived from two sphenopalatine branches of the maxillary nerve; their fibers, for the most part, pass directly into the palatine nerves; a few, however, enter the ganglion, constituting its sensory root.

Motor root
Its motor root is derived from the nervus intermedius (a part of the facial nerve) through the greater petrosal nerve.

In the pterygopalatine ganglion, the parasympathetic fibers they form synapses with neurons whose postganglionic axons, vasodilator and secretory fibers, are distributed with the deep branches of the trigeminal nerve to the mucous membrane of the nose, soft palate, tonsils, uvula, roof of the mouth, upper lip and gums, and to the upper part of the pharynx. It also sends postganglionic parasympathetic fibers to the lacrimal gland via the zygomatic nerve, a branch of the maxillary nerve (from the trigeminal nerve) which then connects with the lacrimal nerve (a branch of the ophthalmic nerve, also part of the trigeminal nerve) to arrive at the lacrimal gland.

Sympathetic root
The ganglion also consists of sympathetic efferent (postganglionic) fibers from the superior cervical ganglion. These fibers, from the superior cervical ganglion, travel through the carotid plexus, and then through the deep petrosal nerve. The deep petrosal nerve joins with the greater petrosal nerve to form the nerve of the pterygoid canal, which enters the ganglion.