Postganglionic sympathetic fibres ascend from the
superior cervical ganglion, along the walls of the internal carotid artery, to enter the internal carotid plexus. These fibres are then distributed to deep structures, including the
superior tarsal muscle and
pupillary dilator muscle. It includes fibres destined for the
pupillary dilator muscle as part of a neural circuit regulating
pupillary dilatation component of the
pupillary reflex. Some fibres of the plexus converge to form the
deep petrosal nerve. The internal carotid plexus communicates with the
trigeminal ganglion, the
abducent nerve, and the
pterygopalatine ganglion (also named sphenopalatine); it distributes filaments to the wall of the
internal carotid artery, and also communicates with the
tympanic branch of the
glossopharyngeal nerve. The plexus there occasionally presents a small gangliform swelling - the
carotid ganglion - on the under surface of the artery. ==Additional images==