Heart Development
Main articles: Heart development and Human embryogenesis
The heart is the first functional organ to develop and starts to beat and pump blood at about three weeks intoembryogenesis. This early start is crucial for subsequent embryonic and prenatal development.
The heart derives from splanchnopleuric mesenchyme in the neural plate which forms the cardiogenic region. Twoendocardial tubes form here that fuse to form a primitive heart tube known as the tubular heart.[20] Between the third and fourth week, the heart tube lengthens, and begins to fold to form an S-shape within the pericardium. This places the chambers and major vessels into the correct alignment for the developed heart. Further development will include the septa and valves formation and remodelling of the heart chambers. By the end of the fifth week the septa are complete and the heart valves are completed by the ninth week.[7]
The embryonic heart begins beating at around 22 days after conception (5 weeks after the last normal menstrual period, LMP). It starts to beat at a rate near to the mother’s which is about 75–80 beats per minute (bpm). The embryonic heart rate then accelerates and reaches a peak rate of 165–185 bpm early in the early 7th week (early 9th week after the LMP).[21][22] After 9 weeks (start of the fetal stage) it starts to decelerate, slowing to around 145 (±25) bpm at birth. There is no difference in female and male heart rates before birth.[23]
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