sino-atrial

sino-atrial |ˌsʌɪnəʊˈeɪtrɪəl | ▶adjective Anatomy relating to or denoting a small body of specialized muscle tissue (the sino-atrial node ) in the wall of the right atrium of the heart, whose contractions regulate the heartbeat. ORIGIN early 20th cent.: from sinus + atrial (see atrium ).