The sinoatrial node is a part of the electrical system of the heart. The development of the sinoatrial node is from the sinus horn myocardium in fetal development.
when you get done with the first stage
Nerves begin to develop in a fetus during the first trimester of pregnancy, around 5-6 weeks gestation.
Nerves begin to develop in a fetus during the first trimester of pregnancy, around the 3rd to 4th week after conception.
In the first trimester it's usually because there's something wrong with the embryo/fetus and it wouldn't survive.
The embryonic period extends to the end of the eight week. After the embryonic period (8weeks), the developing human is called a fetus.
For the first 8 weeks the developing human is called an embryo after that it is called a fetus.
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The fetus gets all the oxygen he needs from the mother's blood by way of the umbilical cord. After birth, he must take his first breath and he will cry at the same time. This crying causes him to take in more air. The lungs will begin to work just as they do now in you.
The heart is the first organ to develop in a fetus. Together, blood and the circulatory system, that is powered by the heart, form the first organ system.
The p wave represents the first electrical impulse to the atria (from Bachmann's Bundle in the sinoatrial node).
Embryo
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