PSYB20H3 Chapter Notes - Chapter 3: Prenatal Development, Low Birth Weight, Embryonic Disc
Document Summary
Zygote embryo fetus: before and after birth, development processed according 2 fundamental principles, cephalocaudal principle: occurs from top to bottom (head to the legs, etc. , proximodistal principle: occurs from center to outer (heart to nails, etc. ) Includes the first 2 weeks of development after fertilization. The zygote divides, becomes more complex, and is implanted in the wall of the uterus. Within 36 hours after fertilization, the zygote goes through mitosis: rapid cell division and duplication. As the fertilized egg is dividing, it is also making its way from fallopian tubes to the uterus (takes. Its form changes into a blastocyte: fluid sphere that floats freely in the uterus until the 6th day after fertilization when it implants itself on uterus. Only 10-20% of fertilized eggs complete implantation and development. Before implantation, the embryonic disk -- a thickened cell mass around the blastocyte forms. The organs and major body systems such as respiratory, digestive, and nervous develop rapidly.
