4. Prenatal Devt and Birth Flashcards
prenatal development
the changes that transform the fertilized egg into a newborn human
how long is prenatal gestation?
38 weeks, +/- 5 weeks (on average)
what are the 3 stages of prenatal devt?
- zygote
- embryo
- fetus
zygote
a fertilized egg
how long is the zygote period?
about 2 weeks. ends when the zygote implants in the uterine wall
implantation
when the zygote burrows into the uterine wall
how long does implantation take? what happens?
about a week.
- the zygote burrows into the uterine wall and connects with the mother’s blood vessels.
- Hormonal changes are triggered that prevent menstruation.
- cells begin to differentiate.
germ disk
a small cluster of cells near the zygote’s centre that develops into a baby
placenta
the organ that exchanges nutrients and wastes between mother and baby
embryo
an embedded zygote (second stage)
what is the period of the embryo? what happens?
weeks 3-8
body structures and internal organs develop
ectoderm
the outer layer of the embryo that will become the hair, outer skin, and nervous system
mesoderm
the middle layer of the embryo that will become the muscles, bones, and circulatory system
endoderm
the inner layer of the embryo that will become the digestive systems and lungs
amniotic sac
the sac in which the baby develops (amnion)
amniotic fluid
the liquid that fills the amniotic sac and cushions the baby and maintain the temperature
umbilical cord
a cord-like structure containing blood vessels that joins the developing baby through the baby’s abdomen to the mother’s placenta
- the mother/baby blood vessels run close to each other but do not actually connect
- nutrients, oxygen, waste are exchanged
how does growth in the embryonic period happen?
cephalocaudal (top-down) and proximodistal (centre-out)
what is the period of the fetus? what happens?
weeks 9-38
baby grows and bodily systems start to work
cerebral cortex
grows during the fetal period.
it is the folded surface of the brain that regulates many human behaviours.
vernix
a thick, greasy coating on the skin that protects the baby during gestation
what is the age of viability? why?
22-28 weeks
the age at which the baby could survive outside the womb.
most of the systems are adequately developed and functioning.
What are the 3 general risk factors for prenatal devt?
nutrition
stress
age
What 3 areas does weight gain happen?
- 1/3 baby, placenta, amniotic fluid
- 1/3 fat stores
- 1/3 increase in blood, breasts, uterus
spina bifida
a disorder in which an embryo’s neural tube does not close properly during development. A result of inadequate folic acid in early preg.
What is the effect of stress on the baby?
- in animals, chronic stress results in smaller babies with more problems
- in humans, stress correlates with smaller, premature babies
- causes greater harm earlier in pregnancy
1. reduce oxygen to the fetus, increase heart rate & activity
2. weaken immune system -> illness
3. stress -> unhealthy lifestyle (e.g. smoking)
How does the mother’s age effect the pregnancy?
- teenage mothers are less likely to get prenatal care
- older age (40s) increases incidence of high-risk birth
teratogen (3 types)
an agent that disrupts normal prenatal development
- diseases
- drugs
- environmental hazards
what are two ways diseases can affect the baby?
- pass directly from the mother through the placenta
2. the virus is present in the birth canal and attacks at birth
fetal alcohol spectrum disorder (FASD)
a developmental disorder caused by maternal consumption of alcohol during preg