Chapter 4 - Prenatal Development Flashcards
How long are each trimester?
about 4 months
When can you tell someone is pregnant?
around month 5
most families wait to announce until second trimester since chances of random abortion are much lower
What trimester has morning sickness?
first
What is the germinal period? (period of the zygote)
from conception to implantation of the uterine wall
first 2 weeks
going through mass cell division to form blastocyst
- mitosis and meiosis
What is the period of the embryo?
week 3-8
zygote begins to take form of human
once implanted, begin to develop support structures
- amnion, chorion, placenta, umbilical cord
3 cell layers will form rapidly
What forms the placenta? What is its role?
the uterine wall
extremely important - how the baby gets its food and gets rid of waste
many complications around placenta
What is the amnion?
membrane around the embryo for temperature regulation and protection
filled with amniotic fluid from maternal tissue
What is the umbilical cord?
connect placenta to belly button of embryo
What is the chorion?
membrane that attaches to uterine tissues to gather nourishment for embryo
becomes placenta lining eventually
What is the indifferent gonad?
everybody develops the same gonad, Y chromosome triggers reaction to produce testes which produce testosterone
no reaction = ovaries
What are the 3 cell layers that form in the period of the embryo?
ectoderm
- NS (neural tube), skin, hair
mesoderm
- muscle, bone, circulatory system
endoderm
- digestive system, lungs, urinary tract, other vital organs
What happens if a brain fails to form?
encephaly
What are the key outcomes of the second month? (still in period of the embyro)
rudimentary formation of:
- facial features
- skeleton and limbs
brain rapidly develops
indifferent gonad appears
about 2.5cm and 7g
When is the period of the fetus?
week 9-month 9
half of first trimester plus entire 2nd and 3rd
becomes recognizable as human
What is happening in weeks 9-12?
organs rapidly develop
What is happening in weeks 13-24?
movement begins
react to stimuli
What is happening in weeks 25-38?
maturation
regular sleep cycles
- lots of sleep in last 2 weeks
assume fetal position
What are key developmental outcomes in month 3?
able to move but not felt by month
can swallow, digest, urinate
testosterone secreted by testes in male or female genitalia form
- ultrasound can determine sex
What are the key developmental outcomes in the second trimester?
more refined motor actions
- thumb sucking
kicking may be felt by mother
heartbeat can be heard with stethoscope
hair growth appears
visual and auditory senses clearly functional
- can discriminate between sounds
form vermix (protective coating) and lanugo (baby hair)
What are the key developmental outcomes of the 3rd trimester?
“finishing phase”
organ systems mature rapidly
weight gain
age of viability at 22-28 weeks
9th month: move head down with limbs curled (fetal position)
birth!
48-53cm, 3.2-3.6 kg
What is the age of viability?
22-28 weeks
when survival outside the uterus becomes possible
What are teratogens?
environmental factors that affect prenatal development and harm developing fetus
ex. virus, drugs, chemicals
What is a sensitive period?
time when each developing structure is particularly susceptible to damage form teratogens
- recall rapid development during embryonic period - likely most susceptible here
once parts are fully formed, less susceptible to damage
What are environmental hazards? How can the fetus be exposed?
radiation
chemical
pollutants
direct exposure to mother/fetus
indirect exposure from father
- changes chromosomes
What is the recommended weight gain for mothers? Why?
11-14 kg
malnourishment results in small babies
- may disrupt spinal cord development in 1st trimester
- leads to low birth weight in 3rd trimester
What vitamin is crucial for neural tube development?
folate/folic acid
deficit can cause spina bifida
How does the mother’s emotional well-being affect the fetus?
stress = decreased birth weight = birth complications
How does parental age affect the fetus?
risks associated with teen mothers as well as older parents
When is rubella exposure most dangerous? What are the effects?
most dangerous in 1st trimester
blindness, deafness, cardiac abnormalities. mental retardation
What is toxoplasmosis? What are the effects?
parasite acquired from undercooked meat or handling feces from cat
- pregnant women should never change cat litter
effects are cold-like symptoms in adults, but include eye and brain damage in fetus, even miscarriage thereafter
What is thalidomide? What are the effects?
originally marketed to relieve morning sickness but effects very harmful when taken early in pregnancy
severely deformed organs, limbs, facial features
Thalidomide tragedy gave thousands of women’s babies these symptoms
How does cigarette smoking affect the fetus?
slows fetus growth
- associated with low birth weight
cleft lip, abnormal lung function
higher incidence of ectopic pregnancy
possible cognitive deficits
What is FASD?
fetal alcohol spectrum disorder
FAS and FAE
What is FAS?
fetal alcohol syndrome
caused by heavy drinking
microencephaly, malformation, hyperactivity, seizures, below average intelligence and size
What is FAE?
fetal alcohol effects
caused by moderate social drinking
poor motor skills, attention issues, below average intelligence
What are the effects of illicit drugs on the fetus?
marijuana
- emotional, behavioural, academic problems
heroin
- neonatal death, addicted at birth
crack/cocaine
- premature birth, low IQ
What is considered to be prenatal development?
development that occurs between the moment of conception and the beginning of the birth process
What is the blastocyst?
ball of cells formed when fertilized egg first begins to divide
inner layer becomes embryo, outer layer becomes protective/nourishing tissues
How does implantation occur?
tendrils emerge from blastocyst and burrow into uterine wall, tapping maternal blood supply
takes about 48 hours
looks like small blister
What are the odds of implantation being successful?
only 1/2 of fertilized ova are firmly implanted, nearly 1/2 of these are genetically abnormal or fail to develop
3/4 fail to survive initial phase of development
What is the placenta?
site of all metabolic transactions from embryo to mother
carries O2 and nutrients, removes CO2 and metabolic waste
villi prevent blood from mixing
What is the vermix?
white cheesy substance that protects fetus skin from chapping
What is lanugo?
fine hair covering fetus body to help vermix stick to skin
What is the purpose of the uterus contractions over the last month of pregnancy?
tone the uterine muscles
dilate the cervix
help position head in gaps between pelvic bones
What are sleeper effects?
teratogenic effects that may not be apparent until later in life
What STD infections are transmitted to the newborn at birth?
genital herpes
What is the most common preventable cause of intellectual disability?
FASD
