Journey From Zygote To Embryo To Fetus example essay topic

"From the very moment that the sperm hits the egg, a precarious trip on the thin edge of biological extinction has begun" (Ralph Blair, Nevertheless Joy! ). The developing person is no less a wonder after birth than in the womb. The time spent in the womb, before birth, is so amazing. The journey from zygote to embryo to fetus is a beautiful trip. From the union of sperm and egg to birth of the newborn, development progresses in an orderly, though fragile, sequence.

Fewer than half of fertilized eggs, called zygotes, survive beyond the first two weeks (Grob stein, 1979). But for you and me, good fortune prevailed. Beginning as one cell, each of us became two cells, then four- each cell just like the first. Then, within the first week, when this cell division had produced a zygote of some one hundred cells, the cells began to specialize in structure and function. Around ten days after conception, the increasingly diverse cells attach to the mother's uterine wall, beginning approximately thirty-seven seeks of the closest human relationship.

When the zygote's outer part attaches to the uterine wall, it becomes the placenta, through which nourishment passes. In this second prenatal stage, the inner cells become the embryo. The embryo grows and develops rapidly. During the next six weeks, the embryo's body organs begin to form and function.

At forty days, the spine is visible and the arms and legs are beginning to grow. The heart begins to beat and the liver begins to make red blood cells. Five days later, the inch-long embryo's proportions have begun to change. The rest of the body is now bigger than the head, and the arms and legs have grown noticeably. By two months after conception, the embryo looks unmistakably human and is now a fetus. By the end of the second month, when the fetal period begins, facial features, hands, and feet have formed.

By the end of the sixth month, internal organs suc as the stomach have become sufficiently formed and functional to allow a prematurely born fetus a chance of survival. By that time, the developing fetus also becomes responsive to sound. As the fetus enters the fourth month, its three ounces could fir in the palm of one's hand. Immediately after birth, infants prefer this familiar voice to another woman's voice or their father's voice (Bushel & others, 1992). This "precarious trip" of prenatal development is one of life's most amazing trips. From conception and the formation of the zygote to the embryo stage to the fetus, life is an incredible journey.

I hope you take a step back and look at your life and realize how extremely lucky you are to live in the world around you.