The beginning Flashcards
What is embryology?
The study of progression from a single cell to a baby - includes molecular, cellular and structural factors
Where does fertilisation occur?
Ampullary region of the fallopian tube
What is embryonic age?
Time since fertilisation
What is gestational age?
Time since last menstruation - embryonic age + 2
What is the germinal stage?
Time from fertilisation to end of the second week
What is the embryonic period?
Time from the start of the third week to the end of the eight week
What is the foetal period?
Time from the start of the ninth week to birth
What is the fertilised egg called over the first few days?
Zygote -> morula -> blastocyst
What is the structure of the blastocyst on day 2?
Zona pellucida
Outer cell mass
Inner cell mass
What has to happen to the blastocyst before it can implant?
Lose the zona pellucida - process known as hatching
What happens to the blastocyst to prepare for implantation?
Loses the zona pellucida
Outer cell mass becomes trophoblast
Inner cell mass migrates to top of blastocyst
Formation of blastocyst cavity
What is the function of the trophoblast?
Becomes the yolk sac and placenta - provides nutrition
What is histiotrophic nutrition?
Nutrition provided to the embryo not from maternal blood - up to 12 weeks
What is haemotrophic nutrition?
Nutrition provided by the mothers blood
What does the inner cell mass split into in day 3/4?
Embryoblast
Primative endoderm
What day does implantation typically occur?
Day 6
What happens on day 8?
Trophoblast differentiates into
- cytotrophoblast
- syncytiotrophoblast
Embryoblast differentiates into
- hypoblast
- epiblast
What forms the bilaminar disc?
Hypoblast
Epiblast
What happens on day 13?
Hypoblast produces the yolk sac and chorionic cavity
Amniotic cavity forms within the epiblast
What is week 2 known as?
Week of 2s
Why is it known as the week of 2s?
Trophoblast differentiates into 2 layers
- cytotrophoblast
- syncytiotrophoblast
Embyroblast forms 2 layers
- epiblast
- hypoblast
Hypoblast contributes to the formation of 2 cavities
- yolk sac
- chorionic cavity
