2007-06-06 18:45:53 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Biology
Human heart beat in the human embyo, starts exactly ath the end of the thirs day of intrauterine life (21 days with 1 day plus or minus) and heart beats are detectable with ultrasound by week 4-5-
At that time, chambers of the heart are not yetdefinite, and the cushions and septa are forming, and developing.
There is not a mature and functional "conduction" systems with atrial node, fascicle of His nor branches of purkinje,,, they are being formed at that time...
The heart of the embryo, works by the stimulus of "returning blood", that is, the volume of returning venous blood, in the four primordial embrionic veins, are the main stimulus for contraction till week 6 in which we can say that a proper tissue or "pacemaker" and conduction systems are formed and working-...
2007-06-10 13:47:21 · answer #1 · answered by Sehr_Klug 50 6 · 0⤊ 0⤋
Foetal heart beat begins spontaneously in the embryonic SA node at 7th week of pregnancy. No other cardiac chamber differentiation occurs at that early time.
2007-06-07 01:56:47 · answer #2 · answered by J.SWAMY I ఇ జ స్వామి 7 · 0⤊ 0⤋