I.
Prenatal Development
A.
Germinal Period - Conception to 2 weeks
1. Creation of the zygote
2. Continued cell division
3. Implantation - attachment of the zygote to the uterine wall (10 days after conception)
* Blastocyst - inner cells (embryo)
* Trophoblast - outer layer (placenta/umbilical cord - life supports systems)
B.
Embryonic Period - 2 to 8 weeks after conception
1. Cell differentiation intensifies, support systems for cells form and organs appears
2. Attached zygote becomes embryo
* Endoderm (digestive/respiratory systems)
* Mesoderm (circulatory system, bones, muscles, excretory system, reproduction system)
* Ectoderm (nervous system sensory receptors, skin parts such as hair and nails)
C.
Fetal Period - 8 weeks after conception until birth
1. Fetal size increases and organs start functioning
2. Reflexes appear and there is sexual differentiation
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