Chapter 2: Prenatal Development and Newborns Flashcards
Gamete
Sex cell (egg or sperm) with 23 chromosomes
Zygote
Combinations of both gametes, 46 chromosomes, grows via mitosis (cell division)
Day 4 of fetal development
The inner cell mass of the zygote is arranged into a hollow sphere (where identical twins split from)
End of week 1 of fetal development
The zygote has implanted into the uterine lining; differentiation begins
Week 2 of pregnancy
Inner cell mass of the zygote differentiates into three layers
After zygote has implanted into the uterine lining:
The neural tube is created, which eventually becomes the brain and spinal cord
Epigenesis
Aristotelian belief that the parts of the human body develop in succession
Cell migration
Movement of newly formed cells to a new location in the body/growing embryo
Cell differentiation
Embryonic stem cells specialize to become different cell types (underlying process unknown)
Apoptosis
Programmed cell death
Cephalocaudal Development
The areas of the fetus closer to the head form faster than those far from the head
Embryo at 4 weeks
Four folds in front head develops, primitive heart forms and pumps blood, arm and leg buds emerge
Embryo at 5.5 - 8.5 weeks
Nose, mouth, and palate differentiate (where cleft palate can form)
Fetus at 9 weeks
Rapid brain growth, all internal organs present, sexual differentiation occurs, eyes and ears forming, fingers and toes present
Fetus at 11 weeks
Heart develops to basic structure, spine and ribs are visible, major divisions of the brain form
Fetus at 16 weeks
Lower body growth accelerates, external genitals developed, fetal movement increases (primitive breathing motion)
Fetus at 18 weeks
Fine hair and greasy coating covers the body, facial expressions and sucking reflex can be observed
Fetus at 20 weeks
Oriented to head-down position, massive weight gain period
Fetus at 28 weeks
Triple in weight, brain and lungs fully developed, has reached the point of viability. Increased eye movement and neural activity. Auditory systems are developed and functioning
Placenta
Semipermeable defensive barrier for the fetus, provides hormones (progesterone and estrogen) and nutrients; can affect the baby and the mother
Hemochorial placenta
Inside the uterus; rewires the endometrium to reroute bloodflow to the baby, paralyzes the mothers arteries. Considered an ‘invasive’ placenta, which is comprised of fetal cells (that can become part of the mother’s organs forever)
Rates of miscarriage
1/3 pregnancies miscarry. 2/3 of that 33% occur before the pregnancy is even detectable. 25-50% of women experience a miscarriage. 6-15% of clinically recognized pregnancies end in miscarriage.
Non-genetic effects on prenatal development
Mother’s emotions, teratogens, mother’s health
O’Connor et. al. study
2002; Studied affects of maternal stress during pregnancy on behavior at 4 years old. Found a relationship between high stress levels and high behavioral issues. Many confounds (mental health, time gap, genetic predisposition to stress, socio-economic status, etc.)
DiPietro et. al. study
2002; measured fetal behavior as a response to maternal stress. More stress associated with a more active fetus, which relates to more behavioral issues at 4 years old. Directional issue with this relationship
Teratogen
materials that affect a fetus. Caffeine, alcohol, cigarettes, illegal drugs, etc. Unethical to study; not causal
Fetal Alcohol Spectrum Disorder (FASD)
Related to maternal alcoholism. Impaired cognition, facial deformity, and other problems arise. Baby cannot metabolize the alcohol in the mother’s bloodstream
Critical period for teratogens
Each developmental process has a critical period that can be affected by teratogens. Duration and time of exposure can lead to different affects on the fetus.
Fetal behaviors in utero
Movement begins between 5-6 weeks, then slows with growth due to lack of room and increased sleep time
Vestibular system development
Begins around 5 months, fully develops at birth
Visual system development
Begins at 26 weeks, fully develops after birth with visual stimuli. Babies are born nearsighted. Can be measured by reading heartrate change when exposed to light in utero
Auditory system development
Develops by the end of the second trimester. Babies’ uterine environment is very loud, but they show a preference to hearing their mother’s voice
Taste/smell development
Amniotic fluid can have a taste/smell based on mother’s diet, and can lead to preferences before/directly after birth
Habituation approach to studying fetal learning
Watch for changes in signals after a baby has habituated to a certain stimulus. Amplitude of sucking, preferential looking/head-turn, and heart rate measurements.
Salk heartbeat experiment
1973; 3 groups of babies, one heard normal heartbeat, one heard fast heartbeat, and control heard no heartbeat. Fast group babies got upset, slow/normal group babies gained more weight and cried less than the control group
DeCasper and Spense experiment
1986; studying fetal learning to sounds. Pregnant mothers read a story to their fetuses. When the babies were born, their sucking amplitude was measured when exposed to the familiar story and the novel story. Found infants preferred the familiar story.
Six stages of newborn arousal
Quiet sleep (8 hrs), active sleep (8 hrs), drowsing (1 hr), alert awake (2.5 hs), active awake (2.5 hrs), crying (2 hrs)
Newborn sleep
Babies sleep around 16 hours a day, twice as much as adults. They spend 50% of their sleep time in REM sleep, and their sleep state switches more dramatically
Infant crying
Cry for 2 hours a day. Crying peaks at 6 weeks old, then decreases to 1 hour a day during the first year. Begins as random, becomes more communicative with age.
Colic
Unknown reason for extreme increase in crying in infants. Usually ends around 3 months of age.
Low birth weight
Premature babies are born before 35 weeks gestation. Have a weight of less that 5.5 pounds. Can be caused by malnutrition, teratogens, or being a multiple (twin or triplet)
Effects of low birth weight
Immature organ development, problems thermoregulating. Higher risk of child abuse in the long term.
Apgar test
Easy way to asses the health of a newborn directly after birth. Common practice in western hospitals.
Multi-risk models
Risk factors tend to occur together. The more risk factors compound on an infant, the more likely their development will be affected
Fetal learning
Fetuses habituate to stimuli in utero. They can learn general sounds and rhythms, but not specific content about language, music, etc.
