Stem Cells: A Review
Stem cells are cells which develop into other cell types in the body during early life and growth. They serve as a repair system in the body by continually dividing and producing new cells When a stem cell divides, each new cell has the potential to differentiate (become) a stem cell or differentiate into another type of cell with a more specific function, such as a muscle cell, a red blood cell, or a brain cell.
Stem cells are different from other cell types due to two important characteristics. First, they are undifferentiated cells capable of renewing themselves through cell division. Second, under certain conditions, they can be induced to become tissue- or organ-specific cells with special functions. In some organs, such as the gut and bone marrow, stem cells regularly divide to repair and replace worn out or damaged tissues. In other organs, however, such as the pancreas and the heart, stem cells only divide under special conditions.
There are two different types of stem cells: embryonic stem cells and adult stem cells. Salivary gland stem cells are adult stem cells.
Source: http://stemcells.nih.gov/info/basics/basics1.asp
