Source : Webster's Revised Unabridged Dictionary (1913)

Vitals \Vi"tals\, n. pl.
   1. Organs that are necessary for life; more especially, the
      heart, lungs, and brain.

   2. Fig.: The part essential to the life or health of
      anything; as, the vitals of a state. ``The vitals of the
      public body.'' --Glanvill.

Source : WordNet®

vitals
     n : a bodily organ that is essential for life [syn: {vital organ}]