Transcript or Germinal Period - People Server at UNCW

Lecture Outline
• Conception
• Periods of Prenatal Development
– Period of the zygote
– Period of the embryo
– Period of the fetus
• Conception
– Ovulation: Release of ovum (egg) from one of
a woman’s two ovaries
• Occurs approximately every 28 days
• Egg moves through one of the fallopian tubes
toward the uterus
• If sexual intercourse occurs near ovulation,
conception can occur
– A sperm must penetrate the outer membrane of the egg
» Each sperm and egg cell has only 23 chromosomes
» When merged, the resulting cell has 46 chromosomes
• Conception usually occurs in the fallopian tube
• Fertilized egg is called a zygote
Period of the Zygote (or Germinal Period)
• Lasts about 2 weeks, from conception through
implantation
• Zygote undergoes mitosis (cell duplication) as it
travels down the fallopian tube to the uterus
• By approximately the 4th day after conception, the
zygote has become a blastocyst
– Fluid-filled ball of cells
Two parts of the blastocyst:
• Inner cell mass: Cells on the inside of the
blastocyst
– Will become the embryo
• Trophoblast: Cells on the outside of the
blastocyst
– Will develop into tissues that protect and nourish the
embryo
• Implantation of the blastocyst into the
uterine wall begins approximately 7 to 9
days post-conception
• Support structures begin to develop from
the trophoblast after implantation
• Teratogen: Any environmental agent that
can cause damage during the prenatal
period
General Principles of Teratogenic Effects:
• Dose: Larger doses over longer time periods
usually have more negative effects
• Heredity: The genetic makeup of the mother
and embryo/fetus influence the effect of a
teratogen
• Timing: Effects of a teratogen vary with the
age of the organism at the time of exposure
– Sensitive Period: Time during which basic
structures are being formed
• Each major organ system has its own sensitive
period
– An organ system is most vulnerable to teratogens during
its sensitive period
• Cumulative Risk: Effect of a teratogen may
be worse if there are other risk factors
present (e.g., poor nutrition, lack of medical
care, other teratogens)
Article: Brown et al. (2004)
Hypotheses:
1. Users would differ from non-users
•
Users: Lower socioeconomic status; greater obstetric
risk
2. Children prenatally exposed to cocaine would
differ from children without exposure in social
development, but not in physical or cognitive
development
Within group of women who used cocaine:
3. Mothers who did not keep custody of their
children after birth would differ from
mothers who did keep custody
•
•
Heavier prenatal drug use, lower SES, greater
obstetric risk in mothers who did not have
custody
Their newborns would also show more birth
complications (e.g., prematurity)
Within group of children with PCE:
4. At 2 years of age, children in non-parental
care would differ from children in parental
care:
•
Non-parental care would be higher-quality
than parental care
•
Children in non-parental care would show
better cognitive and social development than
children in parental care
Findings:
1. Users differed from non-users
2. Children with prenatal cocaine exposure
(PCE) did not differ from children without
exposure in terms of physical, social, or
cognitive development
3. Mothers who retained custody did differ
from mothers who did not retain custody
4. Children with PCE who were in nonparental care:
•
•
Received higher-quality care than children
with PCE who remained with their biological
parents
Showed better social and cognitive
development than children with PCE who
remained with their biological parents