Stem cells are the foundation for every organ and tissue in your body. There are many different types of stem cells that come from different places in the body or are formed at different times in our lives. These include embryonic stem cells that exist only at the earliest stages of development and various types of tissue-specific or adult stem cells that appear during fetal development and remain in our bodies throughout life. Beyond these two critical abilities, though, stem cells vary widely in what they can and cannot do and in the circumstances under which they can and cannot do certain things. This is one of the reasons researchers use all types of stem cells in their investigations. In normal development, the cells inside the inner cell mass will give rise to the more specialized cells that give rise to the entire body—all of our tissues and organs. However, when scientists extract the inner cell mass and grow these cells in special laboratory conditions, they retain the properties of embryonic stem cells. These cells are incredibly valuable because they provide a renewable resource for studying normal development and disease, and for testing drugs and other therapies. Human embryonic stem cells have been derived primarily from blastocysts created by in vitro fertilization IVF for assisted reproduction that were no longer needed. Typically, these stem cells can generate different cell types for the specific tissue or organ in which they live.
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Stem Cell Information
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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. Symmetric division gives rise to two identical daughter stem cells, whereas asymmetric division produces one stem cell and one progenitor cell with limited self-renewal potential. Progenitors can go through several rounds of cell division before finally differentiating into a mature cell. It is believed that the molecular distinction between symmetric and asymmetric divisions lies in differential segregation of cell membrane proteins such as receptors and their associated proteins between the daughter cells. Under normal conditions, tissue stem cells divide slowly and infrequently. They exhibit signs of quiescence , or reversible growth arrest. Infrequent cell divisions also help reduce the risk of acquiring DNA mutations that would be passed on to daughter cells.
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Jump to navigation. An adult stem cell is thought to be an undifferentiated cell, found among differentiated cells in a tissue or organ. The adult stem cell can renew itself and can differentiate to yield some or all of the major specialized cell types of the tissue or organ. The primary roles of adult stem cells in a living organism are to maintain and repair the tissue in which they are found. Scientists also use the term somatic stem cell instead of adult stem cell, where somatic refers to cells of the body not the germ cells, sperm or eggs. Unlike embryonic stem cells , which are defined by their origin cells from the preimplantation -stage embryo , the origin of adult stem cells in some mature tissues is still under investigation. Research on adult stem cells has generated a great deal of excitement.
Stem cells are cells that can differentiate into other types of cells, and can also divide in self-renewal to produce more of the same type of stem cells. In mammals , there are two broad types of stem cells: embryonic stem cells , which are isolated from the inner cell mass of blastocysts in early embryonic development, and adult stem cells , which are found in various tissues of fully developed mammals. In adult organisms, stem cells and progenitor cells act as a repair system for the body, replenishing adult tissues. In a developing embryo , stem cells can differentiate into all the specialized cells—ectoderm, endoderm and mesoderm see induced pluripotent stem cells —but also maintain the normal turnover of regenerative organs, such as blood, skin, or intestinal tissues.
