In multicellular organisms , stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell in a cell lineage. They are usually distinguished from progenitor cells , which cannot divide indefinitely, and precursor or blast cells, which are usually committed to differentiating into one cell type. In mammals , roughly 50— cells make up the inner cell mass during the blastocyst stage of embryonic development, around days 5— These have stem-cell capability. In vivo , they eventually differentiate into all of the body's cell types making them pluripotent.
Jump to navigation. For many years, researchers have been seeking to understand the body's ability to repair and replace the cells and tissues of some organs, but not others. After years of work pursuing the how and why of seemingly indiscriminant cell repair mechanisms, scientists have now focused their attention on adult stem cells. It has long been known that stem cells are capable of renewing themselves and that they can generate multiple cell types. Today, there is new evidence that stem cells are present in far more tissues and organs than once thought and that these cells are capable of developing into more kinds of cells than previously imagined.
Adult stem cells are undifferentiated cells , found throughout the body after development, that multiply by cell division to replenish dying cells and regenerate damaged tissues. Scientific interest in adult stem cells is centered on their ability to divide or self-renew indefinitely, and generate all the cell types of the organ from which they originate, potentially regenerating the entire organ from a few cells. They have mainly been studied in humans and model organisms such as mice and rats. To ensure self-renewal, stem cells undergo two types of cell division see Stem cell division and differentiation diagram.