PSYC 2450 Chapter Notes - Chapter 4: Umbilical Cord, Amniotic Sac, Twin

• School: University of Guelph
• Department: Psychology
• Course: PSYC 2450
• Professor: Carol Anne Hendry

Document Summary

Prenatal development: the changes that transform a fertilized egg into a human. Lasts 38 weeks and is divided into 3 stages. Begins with fertilization in the fallopian tubes; usually within 24 hours after ovulation. Division of the zygote occurs every 12 hours: identical twins: zygote separates into 2 clusters, fraternal twins: 2 clusters are fertilized by different sperm. After 4 days, there are 100 cells which is now called a blastocyst. After 6-7 days, the zygote has entered the uterus and has begun implantation by burrowing into the wall and connecting with the mother"s blood vessels: takes 1 week to complete, prevents menstruation. Germ disc is a small cluster of cells in the center of the blastocyst that develops into the baby. Placenta is a structure used for exchanging nutrients and waste between the mother and fetus; it is the layer of cells closest to the uterus.