The fibers of the motor root of the trigeminal nerve arise from two nuclei, a superior and an inferior. The superior nucleus consists of a strand of cells occupying the whole length of the lateral portion of the gray substance of the cerebral aqueduct. The inferior or chief nucleus is situated in the upper part of the pons, close to its dorsal surface, and along the line of the lateral margin of the rhomboid fossa. The fibers from the superior nucleus constitute the mesencephalic root: they descend through the mid-brain, and, entering the pons, join with the fibers from the lower nucleus, and the motor root, thus formed, passes forward through the pons to its point of emergence. It is uncertain whether the mesencephalic root is motor or sensory.

This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from


Download e-Anatomy

Mobile and tablet users, you can download e-Anatomy on Appstore or GooglePlay.

e-Anatomy on Appstore e-Anatomy on Googleplay