Relationship of development to stem cell type

Types of stem cells and their relationship to normal development. Totipotent stem cells are thought to exist only in the first several divisions of the zygote. Stem cells become more restricted as pluripotent cells once the blastocyst is formed. By the time the primitive streak forms, most cell types in the organism become further restricted to multipotent status, with the exception of embryonic germ cell lines. The cells derived from these later stages in development have been called "embryonic" or "adult" stem cells, to reflect their different potency as stem cells. The unilinear relationship of development to stem cell potential that is depicted here is no longer a rigid dictate as it appears that highly differentiated cells can be reprogrammed to become pluripotent cells.