Saturday, November 12, 2011

Otic Ganglion

The otic ganglion is a flat mass of nerve cell bodies lying below the oval foramen on the medial side of the mandibular nerve, from where sensory and motor fibers (sensorimotor roots) enter the ganglion and pass through without synapsing. Apart from the parotid gland, the fibers of the otic ganglion also supply the buccal and labial glands via the buccal nerve and the inferior alveolar nerve. The preganglionic parasympathetic fibers originate from the inferior salivatory nucleus. They run in the glossopharyngeal nerve and branch off, together with the tympanic nerve, from the inferior ganglion of the glossopharyngeal nerve in the petrous fossula to the tympanic cavity. The fibers leave the tympanic cavity through the hiatus for the lesser petrosal nerve as a fine branch, the lesser petrosal nerve (parasympathetic root). The nerve runs beneath the dura mater along the surface of the petrous bone and reaches the otic ganglion after passing through the foramen lacerum. The fibers of the sympathetic root originate from the plexus of the middle meningeal artery.

The motor fibers from the motor root of the trigeminal nerve pass through the otic ganglion and leave it in the nerve to tensor veli palatini (soft palate) and in the nerve to tensor tympani (for the muscle that tightens the tympanic membrane). Motor fibers for the levator veli palatini from the facial nerve (VII) are thought to run in the chorda tympani and cross over into the ganglion via the communicating branch with chorda tympani. They pass through without synapsing and enter via a communicating branch the greater petrosal nerve, in which they reach the pterygopalatine ganglion. They pass to the palate in the palatine nerves. The postganglionic secretory (parasympathetic) fibers together with sympathetic fibers enter the auriculotemporal nerve via a communicating branch and from here into the facial nerve via another anastomosis. The fibers then ramify in the parotid gland together with branches of the facial nerve.