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what are the 4 periods of gestation?


what develops in the ectoderm?

brain and spinal cord (CNS)

what develops in the mesoderm?

muscles, skeletal system, circulatory system

what develops in the endoderm?

digestive system, lungs, and urinary tract

how long is the embryo in the embryonic period?

one inch

what happens in the germinal period?

fertilized egg travels to uterus
blastocyst implants on wall
placenta begins to form

what happens in the fetal period?

external genitalia begins to form
stimulation of sound and light
begins to feel pain

what is the age of viability?

22-26 weeks

what percent of time is the fetus usually awake?

11-16% of the time

at the end of the fetal period, how long is the fetus and how much will it weight approximately?

18-20 inches long and 6.5-7.5 lbs.

how much does the mother have to be dilated and effaced for expulsion?

10cm dilated and 100% effaced

how many weeks is full term?

40 weeks

what is the final step of birth?

placental birth

what are the two main influences on development during gestation?

genetics and environment

what are the environmental factors that influence gestation?

fetal stimulation
mother's behavior
mother's demographics

what are teratogens?

disease or drugs that influence development

what are three demographics of the mother that influence gestation?


what are influences on development at birth?

medicinal interventions
delivery date
birth weight
childbirth approach

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