The authors continued, stating that “by 143 DGA, the developing heart has the classical helical organization observed in mature mammalian tissue. This was accompanied by an increase in connexin 43 and connexin 40 expression levels, suggesting their role in the development of the ventricular conduction system and that electrical propagation across the heart is facilitated in later gestation.”
Remarkably, the research team found that the most dramatic changes occurred over a four-day period 124 days into the pregnancy. Within this brief period, the muscle tissue of the heart rapidly organizes. Cardiac fibers were laid down to form the helix shape of the heart, within which the four chambers of the heart form. Without this essential architecture in place, the fetal heart cannot survive outside the womb.
