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Help[Opinions] Well, actually
in reply to a message by kappeash
It does have a heartbeat at about 22 days (that's a little over three weeks). You just can't hear it until much later.
The heart is actually the first organ to develop (logically, since cells need blood to grow). It starts off as a few unbeating cells at about 16 or 17 days. At about 22 days, the very primitive heart starts to beat very slowly and very erratically; as the organ starts forming into a recognisable heart, the heartbeats become faster and more and more stable.
Before birth, a valve called the ductus arteriosus is closed in order to shunt most blood away from the lungs (since the lungs are unused in utero, and hence only need a little blood for nutrition). Thus, the heart is not fully developed until after birth, when the infant's first breaths triggers the ductus arteriosus to start closing, thereby allowing blood to access the lungs that are now needed. Full closure may be instantaneous, or it may take a few days. The closure is usually complete enough right after birth to cause the child no problems, though.
If valve doesn't close, it's a birth defect known as Persistent Ductus Arteriosus or Patent Ductus Arteriosus (PDA). It's more common in premature babies, because they're so undeveloped. It is correctable with a relatively minor operation.
More heart development stuff (very fascinating!): http://snipurl.com/ceq4.
Miranda
The heart is actually the first organ to develop (logically, since cells need blood to grow). It starts off as a few unbeating cells at about 16 or 17 days. At about 22 days, the very primitive heart starts to beat very slowly and very erratically; as the organ starts forming into a recognisable heart, the heartbeats become faster and more and more stable.
Before birth, a valve called the ductus arteriosus is closed in order to shunt most blood away from the lungs (since the lungs are unused in utero, and hence only need a little blood for nutrition). Thus, the heart is not fully developed until after birth, when the infant's first breaths triggers the ductus arteriosus to start closing, thereby allowing blood to access the lungs that are now needed. Full closure may be instantaneous, or it may take a few days. The closure is usually complete enough right after birth to cause the child no problems, though.
If valve doesn't close, it's a birth defect known as Persistent Ductus Arteriosus or Patent Ductus Arteriosus (PDA). It's more common in premature babies, because they're so undeveloped. It is correctable with a relatively minor operation.
More heart development stuff (very fascinating!): http://snipurl.com/ceq4.
Miranda
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