BIOLOGY 172 Lecture Notes - Lecture 29: Inner Cell Mass, Germ Layer, Gastrulation
Document Summary
Cleavage - cell division & implantation onto uterus. Organogenesis - cell differentiation & organ development. Cell proliferation - you need to create more cells. Cell movement - moving to new locations. Ex. chicken embryo foot needs apoptosis, if not then webbed feet occur. Cells differentiate - different functions - gradual process. Zygotes are totipotent - gives rise to all cells. Inner cell mass is pluripotent - it will give rise to embryo & make any cell in the body, not the extraembryonic tissues (hence no totipotence) Inner cell mass + ~100 cell sack = blastocyst. Each germ layer is multipotent - can give rise to many types of cells, but less than the inner cell mass cells. Three germ layers make up the gastrula. Some cells in the body aren"t terminally differentiated - stem cells. Skin cell types can become other skin cell types, but not muscle. Embryonic stem (es) cells - derived from the inner cell mass -- pluripotent.
