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30 Cards in this Set
- Front
- Back
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Cells travel through Hensen's node Anterior gives rise to |
Prechordal, mesoderm notochord and anterior somites |
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Middle gives rise to |
Somites, heart, kidneys |
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Posterior gives rise to |
Lateral plate and extraembryonic mesoderm |
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Notochord |
Formed by cells deposited by Hensen's node during REGRESSION Transient mesodermal structure Important for nervous system |
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Epiboly |
Mesoderm and endoderm move inwards Ectoderm migrate to surround the yolk 4 days Cells on the area opaca attatched to vileline envelope Structures such as filopodia and fibronectin are formed |
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End of gastrulation |
Ectoderm surrounds yolk Endoderm displaced hypoblast Mesoderm is between ectoderm and endoderm Anterior posterior gradient |
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Anterior posterior axis specification |
ovum is rotated as passed through oviduct blastoderm at the top and yolks lighter contents up Posterior marginal zone unknown why but equivalent of Nieuwkoops centre |
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Chicken Bcatenin |
stored in blastodisc vg1 gravitate to posterior Koller sickle overlap PMZ becomes "Nieuwkoop centre" Induce nodal |
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Nodal |
Required for primative streak formation Cerberus inhibited by secondary hypoblast inhibits primitive streak (wnt) Hypoblast is replaced by endoblast in PMZ Streak activates lefty which inhibits additional streaks |
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Transplant Hensen's node |
Induction of a new embryo
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Hensons node is like amphibian dorsal blastopore lip |
Cells induce a new embryo when transplanted Induce neural tissue same genes expressed cells become prechordal plate/chordamesoderm |
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Early development in mammals! |
YAY |
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Difficult to study human embryos |
size of human zygote Number of eggs produced Location of development |
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Implantation |
Cleavage begins 24 hours after fertilization, 1 division per day Celia push embryo to uterus Blastocyct sheds zona pellucida and adheres to uterine wall |
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Mammal Cleavage |
Isolecital holoblastic rotational cleavage 1. Slow divisions 2. Rational is different to others 3. Divisions are not symmetrical 4. Genome is activated early - human after 4 divisions |
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Compaction |
Mouse: loose until 8 cell Cleavage 3 blastomeres cluster in a ball and accquire polarity with tight and gap junctions Adhesion molecules - e-cadherin |
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Morula |
16 cell Large group of surface cells and few internal cells Most external cells form trophoblast- chorion - placenta Embryo proper- center of morula becomes inner cell mass and develops into embryo, yolk sac and allantois and amnion |
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ICM 13 cells and trophoblast |
ICM pluripotent Tropho secretes sodium into morula, draws in water, forms cavitation - fluid filled blastocoel Blastocoel expands, ICM to the side, blastocyst formed |
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Positional cues and polarity cues |
Changes in gene expressions and differentiation Oustide cells - asymetrical forms trophoectoderm Inner cells - symetrical forms pluripotent ICM |
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Hatching and implantation |
ZP prevents embryo from implanting in oviduct Sheds when entering uterus Blastocyst sheds a hole and squeezes out - trypsin Binds to uterine epithelium, digest and imbed |
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Mammal gastrulation |
As if large yolk present but uterus and fetal organ chorion are there |
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Bilaminar germ disk |
Epiblast and hypoblast (Made from ICM) Epiblast closest to uterine wall |
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Hypoblast cells form |
Extraembryonic endoderm Cells delaminate to line blastocoel Forms parietal and visceral endoderm |
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Epiblast cells split into |
embryonic epiblast and amnionic ectoderm Amnionic cavity between |
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Trophoblast forms |
cytrophoblast and syncytiotrophoblast Further digestion of uterus and formation of placenta Secrete paracrine factors that attract maternal blood vessels |
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Chorion |
Trophoblast tissue and blood vessels and extraembryonic mesoderm Fuses with uterine wall to create placenta |
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Function of the choiron |
1. Provide nutrients and O2 to fetus 2. Secrete hormones into mother to help her retain the fetus 3. Repress mothers immune response to reject fetus |
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Maternal zygotic twins Before differentiation of trophoblast |
Dichorionic twins - two chorions |
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Maternal zygotic twins After one trophoblast has differentiated |
monochromatic twins that share choiron |
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Maternal zygotic twins after inner cell mass has flattened down to form bilaminar disk stage |
Share the same amnion |
