BIOM1060 Lecture Notes - Lecture 30: Epiblast, Neural Plate, Neural Tube
BIOM1060 24/04/18
EMBRYOLOGY ANATOMY
Embryo: 8 week period (from fertilisation)
Week 1 - Cleavage
- Fertilised egg = zygote
- Zygote encapsulated by zona pellucida
- Zygote first divides 36hrs post fertilisation
oCleavage: rapid division of cells
- Zygote floats freely within uterine tube and into cavity of uterus
Week 1 - Blastocyst and implantation
- Blastomere = cleaved cells
- Morula = loose collection of blastomeres (after cell divided multiple times)
- Blastocyst: morula that’s started to hollow out (cavity forms in middle)
oOuter shell of trophoblast cells placenta
oInner cell mass baby and other tissues
- Zona pellucida breaks down (blastocyst ‘hatches’ from it)
- Blastocyst implantation: triggered when trophoblast cells stick to endometrium (day 7)
oBlastocyst induces inflammatory response in endometrium, which erodes it
oTrophoblast cells invade endometrium and form two cell linages
oImplants high if early, and low if not mature
- 2/3 embryo implantation fail
- Trophoblast cells release human chorionic gonadotropin (HCG) to prevent menstruation
and progress pregnancy
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Document Summary
Zygote first divides 36hrs post fertilisation: cleavage: rapid division of cells. Zygote floats freely within uterine tube and into cavity of uterus. Morula = loose collection of blastomeres (after cell divided multiple times) Blastocyst: morula that"s started to hollow out (cavity forms in middle: outer shell of trophoblast cells placenta, inner cell mass baby and other tissues. Zona pellucida breaks down (blastocyst hatches" from it) Trophoblast cells release human chorionic gonadotropin (hcg) to prevent menstruation and progress pregnancy. Blastocyst forms bilayered embryonic disk (inner cell mass epiblast and hypoblast) By end of week: amnion, yolk sac and chorion formed, and trophoblast cells completely invaded/burrowed into endometrium (trophoblast cells differentiate and rapidly divide to form chorionic villi - help transport nutrients from mum to baby) Three layers fold to become cylinder: curves cephalocaudally (head and tail folds, folds transversely (rounded body form)
