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Chapter 3

PSYB32H3 Chapter Notes - Chapter 3: Amniotic Sac, Umbilical Cord, Teratology

Course Code
Mark Schmuckler

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Psyb20 ch3
Parity is wheter a woman has had a child before
Stages of prenatal development
conception during a woman’s ovulation
the zygote
-the first 2 weeks of life
-the fertilized egg
-it implants on the wall of the uterus
The embryo
-lasts from the beginning of the third week of gestation until the end of the eighth week
-the amniotic sac, membrane around the organisms forms, containing amniotic fluid in which
the embryo floats, and the wall tendrils increase in size forming placenta
-the embryo Is joined to the placenta by the umbilical cord where there is a tramittance of
oxygen and nutrients to the infant, and carbon dioxide is removed
-3 layers: ectoderm (hair, nails, skin teeth and nervous system), mesoderm (muscle skeleton
circulatory system and excretory system) and endoderm (gastrointestinal tract, trachea
bronchia, glands and vital organs)
-cephalocaudal: the development proceeds form the head downward to the trunk and legs
-proximal-distal:growth occurs first in central areas, as internal organs then in more distant
-miscarriages: where the embryo detaches from the wall and expelled through vaginal canal
The fetus
-experiences rapid growth and muscular dev and central nervous system
-end of 3rd month fetus has all of its parts
-by 4th month there is movement and 5 months reflexes
-the fetus will develop lanugo wich is a soft like hair that covers the body
-6 months open and close eyes
-they have a surfactant that allows oxygen from the air into the blood without this some fetus
may develop respiratory distress syndrome
-age of viability: around the age of 22 weeks to 26 weeks where if the baby is born prematurely
it will still be able to survive
Risk in the prenatal environment
-teratogens can affect dev
-the organism is most vulnerable during embryonic stage however each organ system has a
different critical period
-different teratogens influence different developmental processes
-maternal and fetal genotypes affect the developing infant’s response to teratogenic agents and
play a role in determining whether the infant displays abnormalities
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