Module 2: Pregnancy III Flashcards
when does embryogenesis occur?
0 to 8 weeks gestation
first 2 months of pregnancy
embryogenesis overview
Egg is fertilized → zygote is formed (within 24 hours of fertilization) → cleavage
woman might not know she is pregnant yet
embryogenesis stages in order
- cleavage
- blastulation
- implantation
- gastrulation
- neurulation
- growth and development of the fetus
- 0 to 8 weeks
embryogenesis stage 1: cleavage
zygote cleaved into 2 blastomeres
embryogenesis stage 2: blastulation
morula divides to form blastocyte (has inner cell mass)
embryogenesis stage 3: implantation
6-7 days after fertilization
blastocyte penetrates endometrium
we begin to have a difference between inner cell mass and trophectoderm
embryogenesis stage 4: gastrulation
embryo forms blastula (layer of epithelial cells) which reorganizes into gastrula
embryogenesis stage 5: neurulation
neural plate turns into neural tube
this will later form brain and spinal cord (CNS)
This allows for organogenesis
Tissues begin differentiated, we get different cell types
Folate is key in neurulation
week 4 major step
heart does “practice beatings” (no heartbeat is heard yet)
The practice/testing happens so if things are not working correctly the pregnancy can self-terminate
week 5
Week 5: we see more organ systems (still no heartbeat on ultrasound)
which stage has more growth, fetal or embryo?
fetal stage
at what week is embryo considered a fetus
week 9
when does fetal development occur?
8 to 38/40 weeks gestation
why does water decrease in fetus from 30 to 40 weeks
increase in fat and protein mass
More deposition of lean body mass, muscles grow and develop
Fat mass is very important to neonatal period
Babies with not enough fat mass end up in the NICU to control their body temperature
fetal development characteristics
We see increases in weight with each phase of pregnancy
We see primitive sperm or egg cells
After midway through pregnancy we see calcification of skeleton
Towards end of pregnancy we see deposition of many nutrients
Growth declines a bit near term
critical periods of development
finite periods during development in which certain events occur that will have irreversible effects on later developmental stages
key critical periods in fetus
during early embryonic period and embryogenesis (much more than fetal period)
critical periods of development overview
Differentiation: cellular acquisition of one or more characteristics or functions different from that of the original cell
We make a lot of cells, and then get rid of the ones we don’t need
We want to start with too many rather than two few
maternal factors that influence fetal growth
- micronutrient availability
- vitamin D
- antioxidants - inflammation and oxidative stress
- vasoconstriction
- hormone activity
- thyroid
- glucocorticoids - metabolic function
placental factors that influence fetal growth
- implantation
- growth
- mitochondrial function
- epigenetic regulation - nutrient transfer
- transporters
- oxygen gradient - hormone activity
- placental hormones
- regulation of hormone transfer
fetal growth factors
- epigenetics
- organ toxicity
- hormone activity
consequences of inadequate nutrition during fetal development
small for gestational age (SGA)
large for gestational age (LGA)
intrauterine growth restriction (IUGR)
small for gestational age (SGA)
newborn weight is <10th percentile for gestational age
dSGA: Normal head size, smaller body and limbs
Proportionally SGA (pSGA): long-term risk factors
large for gestation age (LGA)
weight for gestational age exceeds the 90th percentile for gestational age or birthweight >4500g