n.天井；前庭；门廊；[解]心房
Both atria are thinwalled muscular chambers. 两心房是由薄壁构成的空腔。
Yet on maximal vagal stimulation, both atria and ventricles come to a standstill. 然而，以最大刺激作用于迷走神经时，心房和心室都停搏。
