Developmental Psychology
Chapter 4: Prenatal Development and Birth
4.1 Prenatal Development
LEARNING OBJECTIVES:
Summarize the main events and three phases of the prenatal period.
Explain the major changes in brain development during the prenatal period.
Conception
Females ovulate every 28 days and midway through that the ovum (egg cell) ripens, exits
the ovary, and travels through the fallopian tube to the uterus. Usually the egg disintegrates
and leaves the body as part of the menstrual fow. However, if during sex the seminal fuid
were to enter the woman, about 300 million or so sperm cells race to the fallopian tube
taking about 6 hours in and out of these one penetrates the egg. This fertlized egg then
keeps any other sperms form entering it. This is called a zygote.
Infertility: the ability of being unable to get pregnant which may be because of a man or a
woman.
Artificial Insemination: involves injectng sperm, either from the womanss partner or from a
donor, into her uterus.
In Vitro Fertiliiation (IVF): is in which several eggs are removed from a womanss ovary and
manually combined with the sperm in a laboratory dish before being returned to a womanss
uterus in hopes that one egg will implant on the wall of the uterus.
Prenatal Stages
Embryologists: experts who study early growth and development.
Embryologists divide prenatal development into three stages or periods (more commonly,
parents-to-be organize pregnancy into trimesters):
1. The germinal period
2. The embryonic period
3. The fetal period
, The Germinal Period
Germinal Period: lasts about 2 weeks. The zygote divides many tmes through mitosis,
forming the blastocyst – a hollow ball of about 150 cells. When it reaches the uterus around
day 6, it implants tendrils to form its outer layer into blood vessels of the uterine wall.
Miscarriage is when pregnancies are short lived.
The Embryonic Period
Embryonic Period: from the 3rd week tll the 8th week. Every major organ takes shape, in at
least a primitve form, in a process called organogenesis. The layers of the blastocyst
differentate, forming structures that sustain development. The outer layer becomes both
the:
- Amnion: a watertght membrane that flls with fuid that cushions and protects the
embryo, and the
- Chorion: a membrane that surrounds the amnion and ataches root-like extensions
called villi into the uterine lining to gather nourishment for the embryo.
The chorion eventually becomes the lining of the placenta – a tssue fed by blood vessels
from the mother and connected to the embryo by the umbilical cord. Through the placenta
and umbilical cord, the embryo receives oxygen and nutrients and eliminates waste and
CO2.
Spina bifida: a conditon in which part of the spinal cord during development is not fully
encased in the protectve covering of the spinal column. The neural tube fails to close,
causing children to have neurological problems ranging in intensity. Failure to close at the
top of the neural tube can lead to anencephaly – a lethal defect in which the main porton
of the brain above the brain stem fails to develop. Testosterone is the primary male sex
hormone that stmulates the development of a male internal reproductve system.
The Fetal Period
Fetal Period: lasts from the 9th week untl birth. Critcal period for brain development
involving three processes: proliferaton, migraton, and differentaton.
Proliferation of neurons involves their multplying at a staggering rate during this
period.
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