atrial sphincter

例句：

1. 1. The atrial sphincter is responsible for preventing blood from flowing backward during the heartbeat.
   心房括约肌负责在心脏跳动时防止血液回流。
2. 2. The atrial septum acts as a barrier between the atria and ventricles, helping to control the flow of blood.
   心房分隔物作为心房和心室之间的屏障，帮助控制血流。
3. 3. Cardiac septum is an important structure in the heart that helps maintain proper functioning.
   心肌分隔物是心脏中的一个重要结构，有助于保持正常的功能。