aorta

noun2

1. •
   The great artery which carries the blood from the heart to all parts of the body except the lungs; the main trunk of the arterial system.
2. •
   (figurative) The liveliest part of something.

   • Tracing their battles, I had many occasions to walk along Second Avenue, the aorta of the Lower East Side, exploring places that were once as vibrant and tumultuous as Midtown Manhattan. — 2007