when does the embryonic heart begin to beat
Heart development Heart development refers to the prenatal development of the human heart. This begins with the formation of two endocardial tubes which merge to form the tubular heart, also called the primitive heart tube, that loops and septates into the four chambers and paired arterial trunks that form the adult heart. The heart is the first functional organ in vertebrate embryos, and in the human, beats spontaneously by week 4 of development.[2]
When Calls the Heart On April 24, 2017, Krakow announced via the Hallmark Channel website that the show would return for a fifth season in February 2018.[6] The season will premiere with a 2-hour Christmas special, to be broadcast as part of Hallmark's Countdown to Christmas season, and continue for a 10-episode season, beginning in February 2018.[7]