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Epigenetics
the emergence of new structures and functions during development.
Cell Division
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.
Embryo
the developing organism from 3rd to 8th week of prenatal development
Fetus
the developing organism from the 9th week to birth
Mitosis
cell division that results in two identical cells
Cell migration
Newly formed cells move away from point of origin.
Cell differentiation
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).
embryonic stem cells
All of the embryo’s inital cells that can develop into any type of body cell
Death (of cells)
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.
Androgens
class of hormones that include testosterone and lead to development of male genitalia.
If there are no androgens, female genitalia develops.
Identical (monozygotic twins)
twins that result from splitting in half of zygote, resulting in each of 2 zygotes having exactly same set of genes.
Fraternal (dizygotic twins)
twins that result when 2 eggs happen to be released into fallopian tube at same time, only have half their genes in common.
What happens in the first week?
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.
What happens by the 2nd week?
the embryo folds into 3 layers.
The top layer → nervous system (nails, teeth, inner ear, lens of eyes, outer surface of skin)
The middle layer → muscles, bones, circulatory system, inner layers of skin, other internal organs
The bottom layer → digestive system, lungs, urinary tract, glands
A few days after the embryo becomes 3 layers, a U-shaped groove forms and folds at the top of this groove fuse, creating neural tube which eventually becomes the brain and spinal cord.
Amniotic sac
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.
Placenta
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)
Cephalocaudal development
pattern of growth in which areas near head develop earlier than areas farther from head
What happens at 4 weeks?
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.
What happens at 5.5 weeks?
the fetus’s nose, mouth, and palate are beginning to differentiate.
What happens at 9 weeks?
the bulging forehead reflects extremely rapid brain growth.
The eyes and ears forming, all internal organs are present, sexual differentiation has started, ribs are visible, fingers and toes have emerged, and nails are growing.
What happens at 11 weeks?
the heart has achieved basic adult structure, spine, ribs, major divisions of brain developing.
What happens during the last 5 months?
external genitalia is mostly developed
What happens at 18 weeks?
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
What happens at 28 weeks?
the brain and lungs are sufficiently developed .
The eyes can open and move, esp. during REM
The fetus reacts to variety of sounds
What happens during the last 3 months?
the fetus grows 3x it’s weight
What happens during the first trimester?
1 - Zygote travels from fallopian tube to womb and embeds in uterine lining; cells arrange into a ball and begin to form embryo and support system 2-3: embryo forms 3 layers and neural tube develops. 4: neural tube develops into brain and spinal cord, primitive heart visible, leg and arm buds too. 5-9: facial features differentiate; rapid brain growth occurs; internal organs form; fingers and toes emerge; sexual differentiation has started. 10-12: heart develops basic adult structures; spine and ribs develop more fully; brain forms major divisions
What happens during the second trimester?
13-14: lower body growth accelerates; external genitalia are fully developed; body develops hairy outer covering; fetus can make basic facial expressions; fetal movements can be felt by mother.
What happens during the 3rd trimester?
25-38: fetus triples in size; brain and lungs are sufficiently developed at 28 weeks to allow survival outside womb; visual and auditory systems functional; fetus capable of learning & behaviours begin to emerge.
Fetal movement
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
Fetal touch
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.
Fetal sight
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.
Fetal Taste
Amniotic fluid actually has many flavours, and fetuses have preferences.
For example, some fetuses have a sweet tooth.
Fetal Smell
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.
Phylogenetic continuity
the idea that because of our common evolutionary history, humans share many characteristics, behaviours, and developmental processes with non-human animals, especially mammals
Prenatal Hearing
Uterine auditory experience is very good for early brain development, and because sound is so prevalent in the womb, it plays a major role in prenatal learning.
Fetal Learning
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
Habituation
Fetuses grow bored if a stimulus is repeated over and over again
Dishabituation
the introduction of a new stimulus which rekindles interest following habituation to the repeated stimulus.
Teratogens
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.
Fetal programming
Late effects of prenatal experience that program physiological set points that are important to adulthood physiology.
Sleeper effects
when the issues don’t show up until years later.
Effects of antidepressents on fetuses
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.
Effects of opioids on fetuses
Opioids have the potential to hurt the developing brain.
They can even cause fetuses to become addicted themselves.
Neonatal abstinence syndrome
________ (NAS) is drug withdrawal seen when fetuses are exposed to opioids in the womb after birth.
Effects: Low birth weight, problems with breathing and feeding, and seizures.
Effects of Marijuana on fetuses
Prenatal exposure to marijuana is associated with problems with attention, impulsivity, learning and memory in older children.
Effects of cigarette smoking on fetuses
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.
Sudden Infant Death Syndrome (SIDS)
the sudden unexpected death of an infant less than 1 year of age that has no identifiable cause.
Effects of alochol on fetuses
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.
Dose-response relationships
the higher the dose, the higher the risk
Maternal factors
age
nutrition
disease
maternal emotional state
Effect of mother’s age on fetus
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.
Effect of mother’s nutrition on fetus
Malnutrition can lead to nutritionally deprived fetuses.
This leads to prematurely aged brains, and impaired performance on attentional tasks.
Effect of mother’s disease(s) on fetus
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.
Effects of maternal emotional state on fetus
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.
Apgar score
method for evaluating health of newborn immediately following birth based on skin tone, pulse rate, facial response, arm and leg activity, and breathing.
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)
Swaddling
wrapping he baby tightly in cloths or blanket. This produces a high level of tactile simulation and warmth.
Low Birth Weight
birth weight less than 5.5 pounds
Colic
excessive, inconsolable crying by young infant for no apparent reason
Steroids
________ like glucocorticoids limit fetal growth and help fetal tissues mature.
Prenatal scent learning
________ is important in many species early development processes, demonstrates principle of phylogenetic continuity (the idea that because of our common evolutionary history, humans share many characteristics, behaviours, and developmental processes with non- human animals, especially mammals)
Dishabituation
________ happens when new stimuli is introduced.
Altered ________ for fetus may lead to long- term changes in how children and and adults cope with stress.
hormonal environment
REM
________ sleep- active sleep state characterized by quick, jerky eye movements under closed lids and associated with dreaming in adults (50 % of total sleep time)
Malnutrition
________ can lead to nutritionally deprived fetuses.
Uterine auditory experience
________ is very good for early brain development, and cause sound is so prevalent in the womb, it plays a major role in prenatal learning.
Accutane
________ is used for acne and can lead to severe birth defects or fetal death.
Mitosis
________- cell division that results in two identical cells.
Non REM
________ sleep- a quiet or deep sleep state characterized by absence of motor activity or eye movements and more regular, slow brain waves, breathing, and heart rate.
last trimester
During ________, external noises elicit changes in fetal movements and heart rate.
State
________- level of arousal and engagement in the environment, ranging from deep sleep to intense activity.
a major influence
Hormones have ________ through prenatal development.
Alcohol
________ in blood crosses placenta into fetus’s bloodstream and amniotic fluid.
Formation of fingers
________ is dependent on death of cells in between ridges in hand plate.
Pregnant women
________ in less wealthy countries report greater levels of stress than those from wealthier countries.
Genital herpes
________ can lead to blindness or even death.
Postnatal maternal stress
________ is a stronger predictor of later outcomes than prenatal maternal stress.
trillions of cells
Zygote becomes newborn consisting of ________.
Cell suicide
________ (apoptosis)- is genetically programmed cell death.
Dose response
________ relationship: risk of negative outcomes for mother and fetus increasing with maternal age.
embryo
the developing organism from 3rd to 8th week of prenatal development
inadequate prenatal nutrition
fetus’s metabolism adjusts to to nutritional deficiency in womb and does not reset after birth, can lead to obesity
dose-response relationship
risk of negative outcomes for mother and fetus increasing with maternal age
state
level of arousal and engagement in the environment, ranging from deep sleep to intense activity
infants are in 6 states
quiet sleep, active sleep, drowsing, alert awake, active awake, and crying
REM sleep
active sleep state characterized by quick, jerky eye movements under closed lids and associated with dreaming in adults (50% of total sleep time)
Non-REM sleep
a quiet or deep sleep state characterized by absence of motor activity or eye movements and more regular, slow brain waves, breathing, and heart rate
swaddling
wrapping baby tightly in cloths or blanket (produces high level of tactile simulation and warmth)
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