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Module 4: Prenatal and Childhood Development . The Beginnings of Life Psych. 12 Ms. Stoski. Genetic and Environmental Marvels . If you are a young woman you were born with all of the egg cells you will ever have, though of course they were immature when you were just a baby.
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Module 4: Prenatal and Childhood Development The Beginnings of Life Psych. 12 Ms. Stoski
Genetic and Environmental Marvels • If you are a young woman you were born with all of the egg cells you will ever have, though of course they were immature when you were just a baby. If you are a young man you did not begin producing sperm until you reached puberty. You will keep producing sperm until you die. Although the growth rates slow with age, you will produce more than 1.5 million sperm cells in 30 minutes, a rate of about 1000 per second.
So how exactly did these young women and men get to be here in the first place????? • It all started when . . . ..
When the sperm penetrates the egg, the egg immediately releases a chemical creating a hard “shell” around it to keep all other sperm out
Zygote Begins to Develop (Germinal Stage) Fertlization to 2 weeks
Zygote • A newly fertilized egg is called a zygote. It enters a 2 week period or rapid cell division and development into an embryo. • Not even one in two zygotes make it past the first 14 days. Luckily, we all survived that risky period! • As you saw the single cell zygote divides into identical cells. One becomes 2 and 2 becomes 4. • After dividing about 7 times in the first week, the cells start to differentiate to specialize in function. • Our genes direct this process and lead some cells to develop into a brain, into lungs, or a heart. • Around the 10th day the zygote enters into the uterine wall, where it will then stay for about 37 weeks. • However, once the zygote passes a 14 day milestone, it is now no longer a zygote, it is an embryo.
Embryo (Embryonic Stage) • Now the baby has a noticeable heart-beat and red blood cells produced by it’s own liver. • The embryonic stage that started at 2 weeks will last until about 8 weeks. • At this time the body’s major organs have been formed. • At 9 weeks the developing organism enters the fetal period.
Fetus • The developing human organism from nine • weeks after conception to birth. • Fetuses born prematurely at the end of 6 • months have organs that are well enough developed to have a chance at survival. • While in the fetus the baby receives oxygen and nutrients from the placenta (a cushion of cells that serves to screen out substances that could harm the fetus). • The placenta is the lining of the uterus that the umbilical cord will attach to. While nutrients and oxygen move across the placental wall, the embryo’s blood and the mother’s blood never mix.
Teratogens • Unfortunately the placenta is not a perfect screen and some viruses, toxins, and drugs do slip through. • Teratogens are substances that cross the placental barrier and prevent the fetus from developing normally. Timing & quantity of the exposure is important Especially problematic during periods of rapid prenatal development Poverty increases the chances of exposure Prescriptions, over the counter drugs, nicotine, alcohol, STD viruses, smoking. RESULTS = Miscarriages, FAS, STDs, physical and mental abnormalities
Newborns • In 40 weeks what was once cell is ready to be born.
Newborns • Within the first ½ hour they will turn their heads to human faces and human voices. They even have a definite taste preference! • Sugar water and mother’s milk? YES please! • Milk with a spoiled taste or smell to it? No thanks! • Rooting reflex: A baby’s tendency, when touched on the cheek, to open the mouth and search for a nipple or something to suck (bottle) for nourishment. This is an automatic, unlearned response.
Newborns don’t have to learn sucking, swallowing, or grasping. These reflexes are survival behaviours, and babies come ‘equipped’ with them. • Even in the first few hours of life a baby’s temperament is evident. Temperament is a stable personality aspect. The most intense pre-schoolers grow up to be intense young adults. Even fearful 2 year olds become shy. • (Think back to the Temperament Survey you took. . . . . ) • In the first few weeks following birth babies display predictable eating and sleeping patterns.
