BIOL10002 Lecture Notes - Lecture 30: Osmosis, Morula, Cadherin
Document Summary
Zona pellucida is very important to keep individual cells together. Day 3-4 individual cells start to develop their own genetic pattern and turn on expression of paternal genes: gradual process, species difference, from early cleavage stages. Start developing polarity and direction to form epithelium. From 8-cell stage - formation of junction between cells to create polarity to start differentiation to different cell types. Compaction individual cells start to compact with each other: lineage choice is made between whether to form a placenta or contribute to the fetus, most important event during this period. Accumulation of fluid: cells start pump in fluid to form cavity, create sodium gradient - pumps sodium in, as soon as the gradient is created, osmosis (water) is created, aquaporins (water) Distinction of epithelial layer placenta; inner cell mass gone. Zona pellucida: protect prevent early implantation before it reaches uterus cavity, support the development of early embryo. Embryo needs to break open zona pellucida before implantation.
