Establishing New Life
At birth, a female newborn has about two million oocytes; by the time she reaches puberty, this number is reduced to about 400,000. Of these, only a tiny fraction, some 400 or so, undergo ovulation as the woman’s body prepares for potential pregnancy each month.
“At the moment of ejaculation, about 300 million sperm enter the vagina,” explains Deepak Chopra. “Of these, only 1% enter the uterus. By the time sperm reach the surface of the egg in the fallopian tube, it’s about 300-500 that actually make contact. Of these, one penetrates the cell membrane by releasing an enzyme that allows it to enter; as soon as it does, the egg, in turn, prevents any other sperm from entering.”
Within hours, the nuclei of the egg and sperm merge, combining the 23 maternal chromosomes and 23 paternal chromosomes into the set of blueprints that will allow this cellular union to create the trillions of cells that will constitute a unique human being. In one tiny fell swoop, your baby’s gender, eye color, hair color, and much more have been determined. Cell division begins, and when the fertilized egg, or zygote, has divided into 16 cells, it is referred to as the morula (“mulberry” in Latin).
The morula travels down the fallopian tube and arrives in the uterus. It now forms a hollow ball called a blastocyst, consisting of 70-100 cells, which then securely anchors itself to the blood-rich lining of the uterus. “At that moment,” explains Chopra, “a whole cascade of events occurs.”
Fewer than one in four fertilized eggs successfully implant as embryos; the odds can worsen depending on maternal health, nutrition, and stress. But once the blastocyst is securely implanted, a precisely choreographed sequence of changes begins to unfold. The cells divide into two types, those that will form the fetus and those that will develop into the placenta and other structures that will protect and nourish the developing fetus while intimately connecting it to its mother.
Chopra explains that “by the time the developing embryo is about 10 days old, it starts to differentiate into three layers,” which resemble a tiny stack of pancakes. “The endoderm will become the liver, lung, and digestive system, the mesoderm will become muscles, bones, kidneys, heart, and the ectoderm will become skin, hair follicles, nails, eyes, central nervous system. So at this very early stage, when the embryo is literally the size of a punctuation point, a period at the end of a sentence, it has already created a plan for the entire architecture of the body.”
Barely 3 weeks after fertilization, a primitive embryonic heart begins to beat. Also forming is the neural tube, which will give rise to the spinal cord, brain, and the rest of the nervous system, which will integrate the actions of all the other systems. Though the embryo is still only the size of a rice grain, it is engaged in a constant and complex two-way conversation with the mother’s body carried out via biochemical messenger molecules.
It has become commonplace to marvel at the astronomical odds against any one sperm joining any given egg to produce a unique individual. And the entire process of conception, growth, and development is indeed a biological marvel. But it is also a marvel that takes place as surely and predictably as sunrise and sunset. Reproduction isn’t a long shot: it’s a sure thing, a force of nature. In fact, it’s the force, in all its extraordinary splendor and complexity, of our natural world.
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Related Health Centers:
Infant Nutrition Health Center, Mother-Baby Bond Health Center, Mother’s Milk Health Center, Monthly Infant Development Calendar Health Center,Weekly Pregnancy Calendar Health Center