CVS Embryology and Embryology recap Flashcards
When is the embryonic age?
Time since fertilisation
When is the gestational age?
Time since last menstruation - fertilisation + 2 weeks
When is germinal stage?
Fertilisation oil end of 2nd week
When is embryonic period?
2nd week to end of 8th week
When is foetal period?
Start of 9th week to 38 weeks
When does a morula form? What is it?
Group of around 16 cells 3-4 days
When does a blastocyst form? What is it?
Around day 4-5 forms an inner and outer cell mass
—> blastocyst
Blastocyst contains: Embryoblast, and primitive endoderm, outer layer of cells call trophoblasts.
What day does implantation occur? What do you need to lose before implantation can occur?
Day 6
Zona pellucida - leads to ‘hatching’
Where does fertilisation normally occur?
Ampulla
What does the embryoblast and trophoblast become?
Embryo blast - early embryo
Trophoblast - yolk sac and placenta
What is histiopathic nutrition? When does it occur?
Histiopathic nutrition is not from maternal blood, it is from uterine glands/tissues etc up until 12th week in embyro
What is haemotrophic nutrition? When does this occur?
From maternal blood this occurs after week 12
Where does placenta normally lie?
Upper posterior wall of uterus
What is placenta previa?
Placenta blocking exit of baby
What happens in week 2 gestation?
“Week of twos”
trophoblasts splits into two layers
1) Hypoblast –> embryonic yolk sac, chorionic cavity
2) Epiblast (will later become 3 germ layers endo, meso, ectoderm)
Together the hypoblast and epiblast are the bilaminar embryonic disc
What is gastrulation?
Forming of the 3 germ layers
What happens in week 3 gestation? What is the role of gastrulation?
Week of threes
Gastrulation - endo meso ectoderm
Gastrulation ensures precursor cells are in the right place to allow for growth of those tissues
Between which weeks is the period of greatest change? What does this mean for congenital abnormalities?
3-8 organogenesis
Means great risk for teratogenesis