Offspring Development
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Transcript of Offspring Development
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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
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Remaining Anatomical Structures:
Vaginal Structures:Fornix: pockets around external osVaginal Orifice: external opening
Vestibular Glands:- secrete mucus for lubrication
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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
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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
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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
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Prenatal DevelopmentEmbryonic Period
Implantation begins around day 6 or 7-Trophoblast secretes enzymes that allow it to bury into endometrium
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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
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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
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Prenatal DevelopmentEmbryonic Period
Neurulation:- Mesoderm cells form rodlike
notochord- Ectoderm folds into neural tube
and neural crest- Embryo = neurula
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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
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Prenatal DevelopmentEmbryonic Period
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Prenatal DevelopmentFetal Period