As it does that it changes the volume of the heart and gives the - creates the pressure that moves blood around your body, so it has that muscular system.

这使心脏的体积发生变化,产生了足以使血液流遍全身的压力,这就是心脏中有肌肉系统的原因

耶鲁公开课 - 生物医学工程探索课程节选