offspring development

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Offspring Development Ovulation Oocyte and corona radiata are expelled Swept into infundibulum of fallopian tube by fimbriae Fertilization may or may not occur Passes into uterus 2 Regions: Body Cervix - opens into vagina by external os - cervical glands secrete mucus that blocks external o 3 layers: Perimetrium - secretes serous fluid Myometrium - muscular layer Endometrium - epithelial and vascular layer

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Offspring Development. Ovulation. Oocyte and corona radiata are expelled Swept into infundibulum of fallopian tube by fimbriae Fertilization may or may not occur Passes into uterus. 2 Regions: Body Cervix - opens into vagina by external os - PowerPoint PPT Presentation

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Page 1: Offspring Development

Offspring Development

Ovulation

Oocyte and corona radiata are expelledSwept into infundibulum of fallopian tube by fimbriaeFertilization may or may not occurPasses into uterus

2 Regions:BodyCervix

- opens into vagina by external os- cervical glands secrete mucus that blocks external os

3 layers:Perimetrium

- secretes serous fluidMyometrium

- muscular layerEndometrium

- epithelial and vascular layer

Page 2: Offspring Development

Remaining Anatomical Structures:

Vaginal Structures:Fornix: pockets around external osVaginal Orifice: external opening

Vestibular Glands:- secrete mucus for lubrication

Page 3: Offspring Development

Prenatal DevelopmentFertilization:

- in uterine tube- hyaluronidase from acrosomes

penetrates corona radiata and zona pellucida- zona pellucida “hardens”-oocyte continues meiosis- nuclei of sperm cell and egg cell

unite = zygoteBlocks to Polyspermy:1.) Fast Block

1 sperm contacts oocyte membraneNa+ channels open and Na+ enters

oocytemembrane depolarizes no other sperm can fuse with

membrane2.) Slow Block

ER releases Ca++signals cortical granules to release

enzymes into space beneath zona pellucida

sperm receptors are destroyedenzymes bind water, swelling layer

and forcing away other attached sperm from oocyte

Page 4: Offspring Development

Prenatal DevelopmentEmbryonic Period

Sperm nucleus travels towards ovum nucleusMitotic spindle forms Pronuclei degenerate and chromosomes formHomologous chromosomes attach to mitotic spindleMitosis continues and first cleavage completes

Page 5: Offspring Development

Prenatal DevelopmentEmbryonic Period

Mitosis continues until morula forms16 cells3-4 day journey to uterus

Blastocyst forms- cells are dividing and differentiating- two portions develop:Trophoblast = contributes to placentaInner Cell Mass = eventually forms embryo- Fluid fills intercellular space

between two layers = blastocyst cavity

Blastocyst is released from zona pellucida

Page 6: Offspring Development

Prenatal DevelopmentEmbryonic Period

Implantation begins around day 6 or 7-Trophoblast secretes enzymes that allow it to bury into endometrium

Page 7: Offspring Development

Prenatal DevelopmentEmbryonic Period

Embryo forms embryonic disc: cells on ventral side = endoderm cells on dorsal side = ectoderm

Primary germ layers - become baby’s tissues

Space between embryo and trophoblast = amniotic cavity (dorsal side)

Chorion - Forms from trophoblast- Later becomes part of

placentaAmnion-expands amniotic cavity until it surrounds embryo

Page 8: Offspring Development

Prenatal DevelopmentEmbryonic Period

Gastrulation:- Occurs during third week of

development- Endoderm depends on yolk sac- Primitive streak thickens along

embryo’s midline, folds inward = mesodermEmbryo = gastrula

Page 9: Offspring Development

Prenatal DevelopmentEmbryonic Period

Neurulation:- Mesoderm cells form rodlike

notochord- Ectoderm folds into neural tube

and neural crest- Embryo = neurula

Page 10: Offspring Development

Prenatal DevelopmentEmbryonic Period

Organogenesis: - Weeks 4-8- Further folding of all

layers results in body cavities and organs

Embryo is considered a fetus at about 9 weeks

Page 11: Offspring Development

Prenatal DevelopmentEmbryonic Period

Page 12: Offspring Development

Prenatal DevelopmentFetal Period