Early embryogenesis Flashcards
What time period defines the pre-embryonic period?
From conception to 2 weeks
What time period defines the embryonic period?
2-8 weeks in utero
What time period defines the foetal period?
9 weeks to birth
What is fertilisation?
Fusion of sperm and egg
Fertilisation causes the beginning of the 2nd mitotic division what happens after this
The egg is activated by an influx of Ca2+ which causes the formation of the diploid chromosomes
What is the membrane surrounding the egg before implantation?
Zona pellucida
What occurs during cleavage?
Egg starts off with 2 cells (blastomere) to a multicellular stage in 3-4 days
What is the fate of the inner blastomeres of the morula?
They will become the inner cell mass
What is the fate of the outer blastomere of the morula?
They will become the outer cell mass
During cleavage water enters the cell what does this cause?
Water enters and pushes cells in the centre to 1 side forming a blastocyst
After the formation of the blastocyst what must occur for survival?
Implantation
Describe the events involved with early implantation
The outer cell mass of the blastocyst forms pillars that attach with the uterine stroma, the cells secrete enzymes and fuse with the uterine stroma
What 2 cell types from from the inner cell mass?
Epiblasts and hypoblasts
What is meant by the inner cell mass from a bilaminar?
Splits into 2 cell layers epiblast on the top, hypoblast on the bottom
What 2 cavities separate the outer and inner cell mass during late implantation?
Above = amnion Below = primitive yolk sac
