1 week: Embryos several days old have stem cells {embryonic stem cell, gestation}| (ES cell). Embryonic stem cells can uptake and insert genes by homologous recombination. Adding altered stem cells can change mice embryos. Mouse blastocysts have inner cell layer, which can culture with fibroblasts or with leukemia inhibiting factor to prevent further differentiation.
1 week: Cells that will make brain and spinal cord first roll into a hollow cylinder {periventricular germ layer}, then multiply around that cavity, and then migrate outwards to form neuroblasts.
1 week: Cells that will make brain and spinal cord first roll into periventricular germ layer, then multiply around that cavity, and then migrate outwards to form brain nuclei {neuroblast}. Later cells pass through earlier cells, so younger cells are on outside.
1 to 3 weeks: Neuroblasts make cell slab {cortical plate} in embryo upper layer. Two hemispheres form around ventricles.
4-Zoology-Development-Stages-Gestation
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Date Modified: 2022.0225