This is the largest of the sympathetic ganglia, being about one inch in length. It is fusiform in outline and lies opposite the second and third cervical vertebrae, between the internal jugular vein and the internal carotid artery.

Branches

(a) Central. (1) Grey rami communicantes to the anterior primary divisions of the first four cervical nerves.

(2) To the petrous ganglion of the glossopharyngeal,

(3) To the jugular ganglion of the vagus.

(4) To the hypoglossal.

(b) Peripheral. (1) Pharyngeal to the pharyngeal plexus (see below).

(2) Superior cardiac. This descends behind the carotid sheath to the thorax, and on the right side enters the deep cardiac plexus. The left nerve crosses the arch of the aorta to reach the superficial cardiac plexus.

(3) External carotid branches which form the external carotid plexus.

(4) Ascending, which accompanies the internal carotid artery through the carotid canal and divides into a lateral portion, the carotid plexus, and a medial portion, the cavernous plexus, The carotid plexus communicates with the abducens and the Gasserian ganglion of the trigeminal.

It gives off the great deep petrosal and the carotico-tympanic. The former unites with the large superficial petrosal from the geniculate ganglion of the facial to form the Vidian, which passes to Meckel's ganglion. The caroticotympanic proceeds to the tympanic plexus in the middle ear. This plexus is made up of the caroticotympanic branch of the glossopharyngeal, and a filament from the geniculate ganglion of the facial. The small superficial petrosal links the plexus to the otic ganglion. The cavernous plexus communicates with the oculo-motor, trochlear, and ophthalmic division of the trigeminal.

It gives twigs to the pituitary body and furnishes the sympathetic root to the ciliary ganglion.