Prenatal Development
Over the course of nine months the beginnings of a new human life starts as a singled celled zygote that with nourishment, care and an ideal set of various factors develops into a complex system of cells that allows for the fetus to maintain homeostasis and function in the world independent from it’s prenatal life source. The fetus transitions through three distinct periods of prenatal development, germinal, embryonic, and fetal arriving at the end of the third trimester with organized systems that allows for regulated functioning. During the course of prenatal periods the introduction of teratogens has the potential to disrupt the natural course of progress, factors associated with the impact of teratogens on the developing fetus include timing, frequency of exposure and additive impact, and the health of the mother during the course of pregnancy. The germinal stage of pregnancy occurs begins with fertilization (day 0) and continues through the second week. In that time the one-celled zygote travels slowly down the fallopian tube towards the uterus while multiplying and dividing (Berger, 2012, p. 90). Cells begin to differentiate into the placenta and the early embryonic mass and prepare to take on various functions. While that occurs, the first task at hand for the blastocyst is implanting itself to the uterine wall where it will take root and continue it’s development. Days 14 through 56 constitute the embryonic stage of development, beginning with implantation. It is in this stage that the most rapid prenatal changes occur as the embryo lays the groundwork for the complex systems it will come to develop (Berk, 2012, 98). It is for this reason that during this stage of pregnancy the embryo is most susceptible to the various teratogens, ranging from maternal illness, drugs, and various other toxins, that find their way across the placenta (Weng, Odouli, & Li, 2008). The first weeks of this period begin with the development of three distinct layers of the
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