Stem Cells and Progenitor Cells

Stem cells are pluripotent or totipotent undifferentiated cells capable of self-renewal through numerous cycles of cell division (proliferation). Stem cells are categorized as embryonic (blastocysts) or adult stem cells (umbilical cord blood, bone marrow).

Stem cells differentiate into progenitor cells, which are more developmentally committed to a cell line than are stems, but which are nevertheless undifferentiated or immature in comparison to those cells that have differentiated and matured into specialized tissue cells. Progenitor cells are multipotent or unipotent.

Tissue damage or immune stimuli can activate progenitor cells through growth factors or cytokines, leading to increased cell division important for the repair process.

[] labeled photomicrograph of bone marrow, diagram of adult stem cell plasticity, diagram of stem cell versus progenitor cell []

bloodbone marrow embryological tissue ọ ectodermmesodermendoderm ф hematopoiesis

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. . . differentiation began 12/21/06