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