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Offspring Development

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

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Offspring Development

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  1. 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 os 3 layers: Perimetrium - secretes serous fluid Myometrium - muscular layer Endometrium - epithelial and vascular layer

  2. Remaining Anatomical Structures: Vaginal Structures: Fornix: pockets around external os Vaginal Orifice: external opening Vestibular Glands: - secrete mucus for lubrication

  3. Prenatal Development Fertilization: - 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 = zygote Blocks to Polyspermy: 1.) Fast Block 1 sperm contacts oocyte membrane Na+ channels open and Na+ enters oocyte membrane depolarizes no other sperm can fuse with membrane 2.) Slow Block ER releases Ca++ signals cortical granules to release enzymes into space beneath zona pellucida sperm receptors are destroyed enzymes bind water, swelling layer and forcing away other attached sperm from oocyte

  4. Prenatal Development Embryonic Period Sperm nucleus travels towards ovum nucleus Mitotic spindle forms Pronuclei degenerate and chromosomes form Homologous chromosomes attach to mitotic spindle Mitosis continues and first cleavage completes

  5. Prenatal Development Embryonic Period Mitosis continues until morula forms 16 cells 3-4 day journey to uterus • Blastocyst forms • - cells are dividing and differentiating • - two portions develop: • Trophoblast = contributes to placenta • Inner Cell Mass = eventually forms embryo • Fluid fills intercellular space between two layers = blastocyst cavity • Blastocyst is released from zona pellucida

  6. Prenatal Development Embryonic Period Implantation begins around day 6 or 7 -Trophoblast secretes enzymes that allow it to bury into endometrium

  7. Prenatal Development Embryonic Period Embryo forms embryonic disc: cells on ventral side = endoderm cells on dorsal side = ectoderm • Chorion • Forms from trophoblast • Later becomes part of placenta • Amnion • -expands amniotic cavity until it surrounds embryo Primary germ layers - become baby’s tissues Space between embryo and trophoblast = amniotic cavity (dorsal side)

  8. Prenatal Development Embryonic Period • Gastrulation: • Occurs during third week of development • Endoderm depends on yolk sac • Primitive streak thickens along embryo’s midline, • folds inward = mesoderm • Embryo = gastrula

  9. Prenatal Development Embryonic Period • Neurulation: • Mesoderm cells form rodlike notochord • Ectoderm folds into neural tube and neural crest • Embryo =neurula

  10. Prenatal Development Embryonic 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

  11. Prenatal Development Embryonic Period

  12. Prenatal Development Fetal Period

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