Blood vessel
From Memory Alpha, the free Star Trek reference
Blood vessels are part of the circulatory system and function to transport blood throughout humanoid bodies.
In 2373, a Pah-wraith possessing Keiko O'Brien threatened Miles O'Brien, that even by destroying a tiny blood vessel in her brain she would destroy all of Keiko's memories and emotions, if he didn't cooperate. (DS9: "The Assignment")
