Sinoatrial (SA) node
窦房结si-no-A-tre-al 
 
        
        释义:
A small mass in the upper part of the right atrium that initiates the impulse for each heartbeat; the pacemaker
Sinoatrial (SA) node
窦房结释义:
A small mass in the upper part of the right atrium that initiates the impulse for each heartbeat; the pacemaker