literal. The base of the heart (as a bodily organ). Obsolete.
The apex of the heart. Obsolete.
a part of some vertebrate hearts into which the veins lead and which empties into the atrium.
The right auricle and right ventricle considered together. Obsolete.
Physiology. A part of the heart that determines the rate at which it beats and where the contractions begin (normally, in humans and other mammals…