PSYC-223 Chapter Notes - Chapter 3: Blastocyst, Prenatal Development, Egg Cell
21 Sep 2016
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Tuesday, December 2, 2014
Chapter 3: Prenatal Development, Birth, and the
Newborn
Period of the Zygote
-Begins when egg is fertilized in the fallopian tube
-Period of rapid cell division
-Ends 2 weeks later when the zygote is implanted in the wall of the uterus
-Placenta is formed between mother and developing organism to provide nutrients and
remove waste
Implantation
-Implantation the burrowing of the blastocyst into the lining of the uterus
•This occurs 10-14 days after conception
•Small, burr-like tendrils emerge from the blastocyst’s surface to gold on and tap into
the mother’s blood supply
!1
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Tuesday, December 2, 2014
•This occurs in only about half of fertilized ova, and only about half of those survive this
stage of pregnancy
•The inner layer of the blastocyst becomes the embryo
Period of the Embryo
-From 3 to 8 weeks after conception
-Body parts are formed during this period
-Embryo rests in the amnion filled with amniotic fluid
-Umbilical cord joins embryo to placenta
Prenatal Structures
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Tuesday, December 2, 2014
-This is a time of extremely fast development
-Week 3: embryonic disk is differentiating into 3 cells layers (ectoderm - outer layer;
mesoderm - middle layer; endoderm - inner layer)
-Neutral tube: primitive spinal cord that develops from the ectoderm and becomes the
central nervous system
-Week 4: the heart has formed and began to beat
-Eyes, ears, nose, and mouth are beginning to form
-Buds that will become arms and legs appear
The Second Month
-During this month, the embryo becomes more human in appearance
-A primitive tail appears, but then is enclosed in protective tide and becomes the tip of
the tailbone
-Week 5: eyes develop corneas and lenses
-Week 7: ears are well formed
•There’s a rudimentary skeleton
•Limbs are developing hands and fingers, then legs do the same
-During this whole month, the brain develops rapidly
-By the end of the embryonic period, the organism experiences its first muscular
contractions
-Week 7 and 8: embryo develops the indifferent gonad, which will develop into the
testes if there’s a Y chromosomes
-The circulatory system begins to function on its own
Period of the Fetus
-From 9 weeks after conception to birth
-Increase in size and systems begin to function
!3
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