Cortex

Noun

 * 1)  The outer layer of an internal organ or body structure, such as the kidney or the brain.
 * 2)  The tissue of a stem or root that lies inward from the epidermis, but exterior to the vascular tissue.

Derived terms

 * cortical
 * cerebral cortex
 * prefrontal cortex

Thesaurus
armature, armor, armor plate, bark, body armor, border, buckler, bulletproof vest, chain armor, chain mail, chitin, circumference, coat of mail, cork, covering, crust, elytron, envelope, epicarp, epidermis, episperm, exterior, external, facade, face, facet, fringe, front, habergeon, harness, hauberk, integument, lineaments, lorica, lorication, mail, needles, outer face, outer layer, outer side, outer skin, outline, outside, panoply, peel, peeling, pericarp, periphery, phellum, plate, plate armor, protective covering, rind, scute, scutum, shell, shield, skin, spines, suit of armor, superficies, superstratum, surface, test, testa, thick skin, top