Module 4 Flashcards
Prenatal Development, Birth, and the Newborn
what is preformationist?
theory of development in which prenatal life starts with a fully formed individual that gets bigger
- nativist
- false
canalization
- refers to developmental reduction in plasticity
- initially cells can become anything (stem cells); as development progresses, it’s harder to change paths
- studies with frogs: you can change a cell’s path by simply moving it- development influenced by neighboring cells
length of pregnancies
- full term at 40 weeks of pregnancy
- 40 weeks since last period, the time from conception to birth is 38 weeks
- conception happens sometime around 2 weeks after last period, but hard to now when (unless IV)
gametes
- eggs and sperm
- eggs are much bigger (largest cell) and all formed prenatally; sperm much smaller and formed throughout lifespan
haploid
- only half the genetic material found in other diploid cells
- contains 23 chromosomes vs. 23 pairs of chromosomes
fertilization and conception
- while millions of sperm are ejaculated, only 200 reach egg
- takes about 6 hours to go 6-7 inches
- when one penetrates, zona reaction occurs, blocks other sperm from entering
- sperm tail falls off and rest goes into egg
zygote
fertilized egg with 23 chromosomes from mom and 23 from dad
what develops first in prenatal development?
- cephalocaudal= head first
- basic first, then more specialized —> arm buds, then hand paddle, then fingers
- important first -> brain and heart
four major developmental processes transform a zygote into an embryo and then into fetus
- cell division = mitosis results in proliferation of cells
- cell mgiration the movement of cells from point of origin to somewhere else in embryo
- cell differentiation transforms the embryo’s unspecialized stem cells into roughly 350 different types of cells
- the selective death of certain cells (apoptosis), also enable prenatal development
- hand development
germinal period
- begins with conceptions and lasts until zygote becomes implanted in uterine wall, rapid cell division takes place
- conception - 2 weeks
- twins determined in germinal period
embryonic period
- following implantation, major development occurs in all organs and systems of body
- 3rd-8th week
- blastocyst implants into uterine wall- now an embryo!
- placenta and amniotic sac form, chemicals released to preserve pregnancy
- most sensitive period of development
- rapid cell division
- major organ forming
- most miscarriages happen here
fetal period
9th week - birth
- continued development of physical structures and rapid growth of the body
- increasing levels of behavior, sensory experience, and learning
monozygotic
- identical; inner cell mass splits
- siblings share 100% genetic material
- usually share same placenta (with own amniotic sacs)
- not always, if split happens in first 2 days —> environmental difference
- if split happens late, may share same sac- risk of umbilical cord entanglement
- very late- conjoined
dizygotic
- fraternal; 2 eggs released and fertilized by 2 diff sperm
- siblings share 50% genetic material
- i.e. no more related than non-twin sibs
- siblings share 50% genetic material
is identical/ MZ twinning hereditary?
no, but tendency for hyper-ovulation can be passed down
is fraternal/ DZ twinning hereditary?
yes
amniotic sac/ placenta
- amniotic sac: filled with amniotic fluid- protects baby, lets it move unhampered by gravity
- placenta: network of blood vessels that allows for exchanging fluids between fetus and mom
- connected to embryo by umbilical cord
- semipermeable- let good stuff in and bad stuff out
- also lets some bad stuff in
- also produces hormones (estrogen, progesterone)
the embryo layers in weeks 2-3
- top: nervous system, nails teeth, inner ear, lens of eyes, outer surface of skin
- middle: muscles, bones, circulatory system, inner layers fo skin, other intestinal organs
- bottom: digestion, lungs, urinary tract, gland
- top layer folds in on itself and becomes the neural tube
- becomes brain and spinal cord
- spina bifida results from closure errors here (taken folic acid)
4 weeks
- primitive heart begins to pump blood
- neural tube (nearly closed)
5.5-8 weeks
- facial development
- cleft palate happens here
6-8 weeks
- 3/4 inch long
- heart has 4 chambers
- fingers and toes visible
- major organs forming
- movement begins (bending spine)
9 weeks
- a fetus!
- extremely rapid brain growth
- all internal organs present
- rudimentary ears and eyes
- fingers and toes present
11 weeks
- 2.5 inches long
- fetal breathing begins
- heart has 4 chambers
- brain has major divisions
- sleep and awake states
- begin period of lower body growth
- sexual differentiation begins
- most spontaneous abortions occur before this point
sexual differentiation
- androgens (including testosterone), are produced by all fetuses, but genetically male fetus (determined entirely by sperm provided by genetic father) produces a lot more
- causes testes to develop; these eventually produce testosterone themselves
- sex chromosomes abnormalities in 1/500 births
why do sex and gender differ?
- sex is genotype
- gender is the phenotype = what is expressed
- gender identity present from age 2 or 3, both cisgender and transgender children identify gender reliably by age 5
congenital adrenal hyperplasia
testosterone in genetic female (xx) can cause male anatomy and brain differentiation
androgen insensitivity syndrome
lack of sensitivity to testosterone in genetic make (xy) causes no male organs; individuals often raised as female