Dictionary
si'no•a'tri•al node'
Pronunciation: (sī'nō-ā'trē-ul, sī"-), [key] Anat.
a small mass of tissue in the right atrium functioning as pacemaker of the heart by giving rise to the electric impulses that initiate heart contractions. Also called
sinus node. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.