Gastrulation/Neurulation/Branchial arches Flashcards
Pregnancy is divided into ___trimesters
3; 3 month periods but doesnt give us info at what precise stage dev embryo is at.
What is happening during weeks 1-2
- Implantation; cell proliferation and migration
2. Zygote fertilization, morula, blastocyst, bilaminar disc,
There are no birth defects in:
in first two weeks of dev; usually defects you get are so severe that if you have it, the embryo is aborted.
What is going on during weeks 3-8
- Gastrulation- get third layer in dev trilaminar disc
- Folding
- Organogenesis: Most organs initiated in this period
- Neurlation
when is there the greatest vulnerability to birth defects
is during 4th-8th week of embryonic dev bc a lot of organs are forming during this period. AKA the first trimester.
When is the fetal period
3th month -9th month; growth and differentiation; birth defects less severe.
When is the gestational age
begins from the first day of last normal menstrual period. Adds 2 weeks to embryonic age.
When is embryonic age
begins at fertilization. Oocyte & sperm nuclei has fused. Happens 2 weeks after last menstrual period.
If no pregnancy thrives, ____degenerates
corpus luteum. Outer part of endometrium buds off and discharges
If pregnancy, it continues to produce estrogen and ___
progesterone.
What are the phases of the ovarian cycle
- menstrual phase (1-7)
- Proliferative phase
- Luteal phase
- Ischemic phase
What are the stages of getting pregnant
- Primary follicle that starts maturing
- Oocyte gets released to fallopian tube
- zygote gets formed and starts dividing.
- As it gets to uterus it forms a blastocyst in posterior wall of the uterus. (zona pellucida has already started disentregating)
5.
how does a blastocyst get formed
2- cell stage, 4 cell stage, 8 cell stage –> morula –> blastocyst
Blastomeres mitotically divide but DO NOT:
enlarge
what are trophoblasts
end up becoming supporting cells for dev embryo
For organism to survive, during dev, it needs to have supp structure. You can’t just have a trophoblast or just an ____. They are not viable on their own!
embryoblast
AS blastocyst gets to endometrium, the trophoblast attaches to endometrium and start to differentiate. The trophoblast gives rise to two structures:
- cytotrophoblast: surround the embryo
- syncytiotrophoblast: multinucleated mass of cells; produces the main protein we use in pregnancy tests and is responsible for producing human chorionic GnRH. (HcG)
What happens during second week?
Concerned primarily with the dev of the bilaminar germ disc.; 2 layers of trophoblast and you get two mesoderms.
Implantation is complete by the end of the ____week
second
At 2 weeks of embryonic dev you get get 2 layers of trophoblast in dev embryo:
- Epiblast/Amniotic Cavity: Layer towards amniotic cavity (top)
- Hypoblast: Layer towards exocoelomic cavity that later becomes yolk sac. (bottom)
What gives rise to supporting tissues?
extraembryonic mesoderm
What happens in third week>
development of the trilaminar germ disc (week of 3)
what is the start of morphogenesis
gastrulation
What do epiblasts and hypoblasts from bilaminar germ disc differentiate into
- Ectoderm; adjacent to embryonic cavity
- Mesoderm:
- Endoderm: close to endoderm.
- Give rise to everything in body