Fertilization and Development So thats what happens after

Fertilization and Development So that’s what happens after!

Fertilization l l l DAY 0 When sperm penetrates egg l Sperm releases special enzymes to do this l Forms a ZYGOTE – FERTILIZATION OCCURS l Recombination occurs: l Combining of genetic info from both parents Occurs in Fallopian tube

Early Development- The First Week Zygote begins to divide, divide l UNDERGOING MITOSIS!!!!!!! l Hopping along the Fallopian Tube trail! l Implantation of zygote in uterus l Occurs around day 7 l

Trail of an Embryo

Close up look at embryo changes

Early Development- Gastrulation l Cells in zygote form into 3 distinct layers l Endoderm: l Digestive and other inner organs l Mesoderm: l Circulatory l Ectoderm: l Nervous l Skin l The cells within each layer will DIFFERENTIATE – MITOSIS!!!! l Become different (skin cells, heart cells, etc. )

Early Development- Gastrulation

OVERVIEW OF EARLY DEVELOMENT

Overview of Early Development: Stage 1 - Fertilization

Overview of Early Development: Stage 2 - Zygote Formation

Overview of Early Development: Stage 3 + 4:

Overview of Early Development: Stage 5: Gastrulation

The Placenta

The Role of the Placenta l l Develops at 3 weeks Placenta is a fetal organ Connects mother and fetus PLACE OF: l RESPIRATION (GAS EXCHANGE) l NOURISHMENT (GETTING NUTRIENTS) l EXCRETION (RID OF WASTES)

First and Second Trimester Dangers!!!! l Critical Development stage l Drugs, alcohol, and medicines can severely damage embryo/fetus l This can halt development or cause major developmental issues l Not taking care can result in miscarriage or severe deformities of child

Later Development 8 weeks = FETUS l Umbilical cord fully formed at 3 months (12 weeks) l Body systems become more specialized l Fetus becomes bigger l Total human gestation period = about 40 weeks (“full term” at 37 weeks) l

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