PSY 23500 Lecture 3:
12 Feb 2019
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Document Summary
Changes that transform a fertilized egg into a newborn human. ~ fertilization ends when the fertilized egg (zygote) implants itself in the wall of the uterus. ~ identical twins = when the zygote separates into two clusters. ~ fraternal twins = (more common) when two eggs are released and each is fertilized by different sperm cells. ~ 4 days zygote consists of about 100 cells (blastocyte) ~ implantation = blastocyte burrows into uterine wall and establishes connection with mother"s blood system. ~ placenta = layer of cells closest to the uterus. ~ blastocyte is completely embedded in uterine wall (embryo) - ectoderm = become the hair, skin, and nervous system (outer layer) - mesoderm = form muscles, bones, and circulatory system. - endoderm = form the digestive system and lungs. - amniotic fluid = cushions the embryo and maintains constant temperature. ~ umbilical cord houses blood vessels that join the embryo to the placenta.
