As long as the beating cells do not touch one another, their beats are independent - some are faster, some are slower. But after two or three days, the myocytes form interconnected sheets of cells that beat in unison. Pores open between adjacent touching cells, making their cytoplasms interconnected. It is these gap junctions that ensure that the connected cells work as one. Thus occurs the "ventricle orgasm", or in lamens terms -- the heart beat.

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