Anatomical junction where subdivisions of two or more neural trees interconnect with one another to form a network through which nerve fibers of the constituent nerve trees become regrouped; together with other nerve plexuses, nerves and ganglia, it constitutes the peripheral nervous system. Examples: cervical nerve plexus, brachial nerve plexus, sacral nerve plexus[FMA]. [ http://en.wikipedia.org/wiki/Nervous_system_plexus ]