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Prenatal DevelopmentPrenatal Development
•Introduction
•Three Stages of Prenatal Development
–Germinal period
•fertilization and implantation
–Embryonic period
•support systems
•general growth/change
•sex differentiation
–Fetal period
•Advantages of Full-Term Fetus
Prenatal DevelopmentPrenatal Development
•Introduction
–Compared to the newborns of other species, human
newborns are quite helpless, dependent and
underdeveloped at birth.
–As a result, much of our development occurs in a rather
stimulating environment, which is both a challenge and a
source of opportunity
–Even so, a great deal of development occurs
prenatally….
Three Stages of Prenatal DevelopmentThree Stages of Prenatal Development
1. Germinal Period: fertilization and implantation
(conception -2 weeks)
–sperm and egg unite to form single-celled zygote
–zygote travels through fallopian tube toward uterus as
cell division by mitosis begins
–by day 4, approximately 60-70 cells, arranged like a
hollow ball, referred to as a blastula
–when blastula reaches uterus, it burrows into the lining
and begins process of implantation, which begins by
about day 6 and takes a few days to complete.
–Implantation initiates the next (embryonic) period.
•Note: ~58% of zygotes fail to implant successfully!
