PSC 140 Lecture Notes - Lecture 3: Inner Cell Mass, Blastocyst, Amnion
9 May 2019
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Document Summary
Fertilization takes place in the fallopian tube. About 9th day attaches to uterine wall (by this time contains 100s of cells) Inner cell mass detaches and forms embryonic disc. About 25% of time there is a failure to implant (leads to miscarriage) Inner cell mass will eventually become the embryo, while the trophoblast will develop into membranes (e. g. , amnion, chorion placenta) that will protect and support the embryo. You can see beginning of cell differentiation: upper half is beginning of embryo (inner cell mass) lower right is beginning of placenta (trophoblast/outer cell layer) Ends when all major organs have developed in primitive form. After implantation the cells in the inner cell mass begin to differentiate: Ectoderm (outer layer) skin, nails, teeth, lens of eye, inner ear, nervous system. Endoderm (inner layer) digestive system and lungs. Mesoderm (middle layer) muscles, bones, circulatory system, ovaries/testes, kidneys. Proximodistal: from middle of organism out to the periphery.
