Embryology: from the first days to the three germ layers
The first weeks of development: fertilisation, cleavage, blastocyst and implantation, gastrulation and the three germ layers with what each becomes, neurulation, and what clinical practice draws from it (ectopic pregnancy, spina bifida, teratogens, twins).
- 39 cards
- 4 topics
- Free
The outline, topic by topic
Each topic is weighted the way the exam weighs it.
- Concepts
- The steps
- Scenarios
- Understand
A few cards from the deck
Fertilisation: what is it?
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The fusion of a sperm and an egg, usually in the ampulla of the uterine tube, forming the zygote.
The zygote is diploid: it combines both parents' chromosomes.
The first steps of development: which step comes after "Fertilisation"?
- Cleavage of the zygote
- Morula
- Blastocyst
- Implantation
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Cleavage of the zygote
From a single cell to the rudiments of the organs in about eight weeks, the embryonic period.
Morula: what is it?
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A solid ball of cells from the zygote's first divisions, around the third or fourth day.
Its name comes from its likeness to a mulberry.
Why is folic acid advised even before conception?
- It makes the placenta grow
- It prevents twins
- It protects the mother's liver
- It reduces the risk of neural tube closure defects, which closes before the pregnancy is often known
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It reduces the risk of neural tube closure defects, which closes before the pregnancy is often known
The neural tube closes towards the end of the fourth week.
Blastocyst: what is it?
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An embryo with a cavity, made of an inner cell mass (future embryo) and a trophoblast (future placenta).
It is in this form that it implants in the uterus.
Why do the nervous system and skin come from the same germ layer?
- By chance
- They come from mesoderm
- The neural tube forms by folding of the surface ectoderm
- Skin comes from the brain
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The neural tube forms by folding of the surface ectoderm
Some diseases therefore affect both the skin and the nervous system.