A question about our first heart beat?

Discussion in 'Biology & Genetics' started by Quantum Quack, Dec 22, 2005.

  1. Quantum Quack Life's a tease... Valued Senior Member

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    Maybe someone could help me with the terminology for the advent of a foetal heart beat.

    When a foetus heart starts to beat.

    I have heard that this is one of the many aspects of pregnancy that has yet to be understood. How the foetal heart starts to beat.
    If someone can tell me the terminology it would be very helpful for further research. Thanks in advance

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  3. valich Registered Senior Member

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    Foetal is a variant of the word "fetal," meaning "the characteristics of the "fetus." A fetus is an unborn child.

    During pregnancy: "You can hear the foetal heartbeat on sonography with colour Doppler from the 9th week onwards. You can feel the foetal movement in the 18th - 19th week of pregnancy." http://www.indiaparenting.com/faqs/pregnancy_baby/foetal_heartbeat.shtml

    So the question is "Why or how does the human fetus's heart start to beat?"

    "The human heart begins to beat and pump blood through the embryo around day 22 of gestation. The electric stimulus that triggers the muscular portion of the heart, known as the myocardium, to contract is myogenic. This means that the contractions arise spontaneously within the myocardium itself, and propagate from cell to cell. Input from the central nervous system can modify the heart rate (the frequency of heart beats), but it does not initiate beats.

    The ability of cardiac myocytes (the cells that comprise the myocardium) to beat is an intrinsic property of these cells. In fact, myocytes removed from the early heart and grown in culture will beat sporadically, and if they become connected to each other, will then begin to beat rhythmically, in unison. As a functional organ, the heart begins to beat very early, even before it has assumed its final form. Interestingly, the heart begins to beat even before structures such as valves and septa (singular: septum; the muscular walls that divide the chambers) have formed! The initial contractions are peristaltic--that is, they proceed in a wave-like fashion along the length of the heart. Later, once the heart has matured and the conduction system has developed, the contractions proceed in an orderly, timed sequence through the different chambers."
    http://www.madsci.org/posts/archives/sep99/937254975.An.r.html

    Although in technical terminology, I think this explains it:

    "Oxygenated blood from the placenta is transportedto the fetus via the umbilical vein, and with a normal blood flow, most of this oxygenated blood enters the leftatrium via the foramen ovale. This allows oxygenated blood to circulate to the heart and the brain. Blood witha low oxygen content is transported back from the right heart to the aorta via the ductus arteriosus, and thus tothe placenta via the umbilical arteries.The normal fetal metabolism is predominantly aerobic, oxygen-dependent metabolism of glucose. Somecellular glucose is stored as glycogen, reserves which appear mainly during the 3rdtrimester. The energyproduced during aerobic metabolism is utilised for fetal activity and for growth....Beat-to-beat variability indicates the ability of the central nervous system to control and adapt thecardiovascular system."
    Source: "HEART RATE TRACINGS:WHAT SHOULD THE ANAESTHESIOLOGIST KNOW?," by RUTH LANDA, Eurpean Society of Anaesthesiologists, June 5, 2004.
    http://www.euroanesthesia.org/education/rc2004lisbon/11RC1.pdf
     
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  5. Quantum Quack Life's a tease... Valued Senior Member

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    Wow, thanks so very much.
    Does this mean that even in an adult the hearts beats are initiated by the myocardium and regulated by the nervous system?
     
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  7. Enigma'07 Who turned out the lights?!?! Registered Senior Member

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    Why is the SA node the pacemaker of the heart?
    a. Highest rate of depolarization
    b. Takes the lead, the rest of the heart responds to it
     
  8. Quantum Quack Life's a tease... Valued Senior Member

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    I'll be upfront about my motive for the question.
    I am exploring the "notion" that the pheno of SIDS and SADS may be related to the failure of what I have now been informed as the beat initiation of the myocardium.
    That Sudden Infant Death syndrome may in some way be the outcome of this failure.
    I am sure that this has been the subject of much research and wonder what the outcome of that research [ myocardium ] may be regarding SIDS?
    It does seem logical that if the hearts beats initiation system was interupted sudden and seemingly unexplainable death would be the result.
    As is obvious by now, my knowledge of this pheno [ SIDS ] is very limited, hence this thread.
     
  9. valich Registered Senior Member

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    It's genetically engineered that way in humans: not in all life forms. The SA node in humans generates spontaneous action potentials. Organisms have four chamber, two chamber, one chamber, or some have no heart, thus no beat: evolution in action.
     
  10. Enigma'07 Who turned out the lights?!?! Registered Senior Member

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    true, but i figured that the term 'our' in the title refered to humans
     
  11. valich Registered Senior Member

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    You're right. I'm out of line by drifting like that. Sorry.
     

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