"sexus" is not in the dictionary.

plexus
noun
°A network or interwoven mass, especially of nerves, blood vessels, or lymphatic vessels.
"1934: I have the sensation of being immersed in the very plexus of life, focal from whatever place, position or attitude I take my stance. — Henry Miller, Tropic of Cancer"
synonyms: rete
nexus
noun
°a form of connection.
°a connected group.
synonyms: bond, link, tie