cortex
noun /ˈkɔːteks/
  /ˈkɔːrteks/
(plural cortices 
 (anatomy) /ˈkɔːtɪsiːz/
  /ˈkɔːrtɪsiːz/
)- the outer layer of an organ in the body, especially the brain- the cerebral/renal cortex (= around the brain/ kidney)
 Word Originlate Middle English: from Latin, literally ‘bark’.