Studied by 3 people
Zygote divides into 2 parts each containing a full complement of genetic material.
Those 2 divide into 4, 4 into 8, 8 into 16…
The zygote becomes a newborn consisting of trillions of cells.
All of embryo’s initial cells - embryonic stem cells - can develop into any type of body cell.
After several cell divisions, they specialize (how it happens is unknown, but location definitely influences its future development).
Cell suicide (apoptosis) - is genetically programmed cell death.
Formation of fingers is dependent on death of cells in between ridges in hand plate.
Death is preprogrammed for cells that disappear from hand plates.
class of hormones that include testosterone and lead to development of male genitalia.
If there are no androgens, female genitalia develops.
the zygote embeds in uterine lining and becomes dependent on mother for sustenance.
Balls of cells start to differentiate
The inner cell mass becomes an embryo.
The rest of cells become the amniotic sac and placenta that help the embryo to develop.
transparent, fluid-filled membrane that surrounds and protects the fetus
is connected to placenta via umbilical cord which is a tube containing blood vessels that run to the fetus.
Supports organs for the fetus
Keeps the circulatory systems of the fetus and the mother seperate.
The semipermeable membrane permits exchange of some materials between them (oxygen and nutrients from mother to fetus, carbon dioxide and waste products from fetus to mother)
embryo is curved so head and the tail-like structure at the end are almost touching.
The primitive heart is visible, and an arm bud can be seen.
the fetus is covered with fine hair, and greasy coating protects its skin from liquid.
The baby can raise its eyebrows, wrinkle its forehead, move its mouth at this point
the brain and lungs are sufficiently developed .
The eyes can open and move, esp. during REM
The fetus reacts to variety of sounds
5-6 weeks after conception, the fetus moves spontaneously.
It hiccups because fetus may be removing air from stomach to make room for milk
It also swallows amniotic fluid
This promotes normal development of palate, and helps the digestive system mature.
Fetal breathing
The fetus moves its chest wall in and out.
Its breathing is infrequent and irregular, but gets steadier and more regular later.
By the 3rd trimester, they “breathe” about once a second
The fetus grasps its umbilical cord, rubs its face, and sucks its thumbs
It bumps against the walls of the uterus.
It responds to maternal movements, suggesting sensory apparatus in inner ear that provides info about movement and balance works before birth.
The fetus can process visual info by 3rd trimester.
The fetus has visual preferences.
A study suggested that infants like to look toward face-like stimuli before being born.
Amniotic fluid actually has many flavours, and fetuses have preferences.
For example, some fetuses have a sweet tooth.
The odors of amniotic fluid is based on what the mother has eaten.
Smells can be transmitted through liquid, and the fetus can smell when amniotic fluid comes into contact with its odor receptors through fetal breathing.
fetuses learn and have memory
they experinece dishabituation
they remember things after birth which is apparent in their preferring their mother’s voices over others
external agents that can cause damage or death during prenatal development. Many only cause damage if present during a sensitive period.
Teratogens often occur in combination.
Evidence towards whether they’re harmful to fetuses or not is inconclusive.
Many women use behavioural interventions like cognitive behaviour therapy & mindfulness-based cognitive therapy instead of medication.
Opioids have the potential to hurt the developing brain.
They can even cause fetuses to become addicted themselves.
The fetus gets less oxygen and metabolizes some cancer-causing agents in tobacco when exposed to cigarette smoking in the womb.
Effects: slowed fetal growth, low birth weight, increased risk of sudden infant death syndrome (SIDS), lower IQ, hearing deficits, ADHD, and cancer.
Alcohol is the leading cause of fetal brain injury.
Alcohol in blood crosses placenta into fetus’s bloodstream and amniotic fluid.
The fetus gets alcohol both directly and indirectly.
The fetus has less ability to metabolize it, so it remains in system longer.
This can result in fetal alcohol spectrum disorder (FASD)
Effects: facial deformities, intellectual disabilities, attention problems, hyperactivity, low birth weight, increased risk for ADHD, delays in cognitive development & school achievement.
age
nutrition
disease
maternal emotional state
Infants born to girls 15 years or younger are 3-4x more likely to die before 1st birthday than those born to mothers 23-29 years old.
Industrialized countries → women with college degrees wait until 30s and 40s to have children.
Dose-response relationship: the risk of negative outcomes for the mother and the fetus increases with maternal age.
This leads to a heightened risk for developmental disorders such as autism spectrum disorder.
Malnutrition can lead to nutritionally deprived fetuses.
This leads to prematurely aged brains, and impaired performance on attentional tasks.
STIs can be harmful
ex. CMV (herpes) can damage fetus’s central nervous system and cause other serious defects like hearing loss.
Genital herpes can lead to blindness or even death.
HIV can be transmitted in the womb or during birth, or even through breast milk for example.
Zika
Mosquito-borne viral infection.
It can make the baby’s head much smaller than expected.
It can lead to hearing, vision loss, and seizures.
The maternal emotional state leads to an altered hormonal environment for the fetus which may lead to long-term changes in how children and and adults cope with stress.
Postnatal maternal stress is a stronger predictor of later outcomes than prenatal maternal stress.
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