Fertilization and Fertilization and DevelopmentDevelopment

So that’s what happens So that’s what happens after! after!

Fertilization DAY 0DAY 0 When sperm penetrates eggWhen sperm penetrates egg

Sperm releases special Sperm releases special enzymes to do thisenzymes to do this

Forms a Forms a ZYGOTE – ZYGOTE – FERTILIZATION OCCURSFERTILIZATION OCCURS

Recombination Recombination occurs:occurs:Combining of genetic Combining of genetic

info from both parentsinfo from both parents Occurs in Fallopian tubeOccurs in Fallopian tube

Early Development- The First Early Development- The First WeekWeek

Zygote begins to divide, Zygote begins to divide, divide, divide divide, divide UNDERGOING UNDERGOING

MITOSIS!!!!!!!MITOSIS!!!!!!!Hopping along the Hopping along the

Fallopian Tube trail!Fallopian Tube trail! ImplantationImplantation of zygote in of zygote in

uterusuterusOccurs around day 7Occurs around day 7

Trail of an EmbryoTrail of an Embryo

Close up look at embryo Close up look at embryo changeschanges

Early Development- GastrulationEarly Development- Gastrulation Cells in zygote form into Cells in zygote form into 3 distinct 3 distinct

layerslayersEndoderm:Endoderm:

Digestive and other inner organsDigestive and other inner organsMesoderm:Mesoderm:

CirculatoryCirculatoryEctoderm:Ectoderm:

NervousNervousSkinSkin

The cells within each layer will The cells within each layer will DIFFERENTIATEDIFFERENTIATE – MITOSIS!!!! – MITOSIS!!!!Become different (skin cells, heart Become different (skin cells, heart

cells, etc.)cells, etc.)

Early Development- GastrulationEarly Development- Gastrulation

OVERVIEW OF EARLY OVERVIEW OF EARLY DEVELOMENT DEVELOMENT

Overview of Early Development:Overview of Early Development:Stage 1- FertilizationStage 1- Fertilization

Overview of Early Development:Overview of Early Development:Stage 2- Zygote FormationStage 2- Zygote Formation

Overview of Early Development:Overview of Early Development:Stage 3 + 4:Stage 3 + 4:

Overview of Early Development:Overview of Early Development:Stage 5: GastrulationStage 5: Gastrulation

The PlacentaThe Placenta

The Role of the PlacentaThe Role of the Placenta

Develops at 3 weeksDevelops at 3 weeks Placenta is a fetal organPlacenta is a fetal organ Connects mother and fetusConnects mother and fetus PLACE OF:PLACE OF:

RESPIRATION (GAS EXCHANGE)

NOURISHMENT (GETTING NUTRIENTS)

EXCRETION (RID OF WASTES)

First and Second Trimester First and Second Trimester Dangers!!!!Dangers!!!!

Critical Development stageCritical Development stageDrugs, alcohol, and medicines can Drugs, alcohol, and medicines can

severely damage embryo/fetusseverely damage embryo/fetusThis can halt development or This can halt development or

cause major developmental issuescause major developmental issuesNot taking care can result in Not taking care can result in

miscarriage or severe deformities miscarriage or severe deformities of childof child

Later DevelopmentLater Development

8 weeks = FETUS8 weeks = FETUSUmbilical cord fully formed at 3 months Umbilical cord fully formed at 3 months

(12 weeks)(12 weeks)Body systems become more Body systems become more

specializedspecializedFetus becomes biggerFetus becomes biggerTotal human gestation period = about Total human gestation period = about

40 weeks (“full term” at 37 weeks)40 weeks (“full term” at 37 weeks)

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