Stem cells have two important characteristics that distinguish them from other types of cells. First, they are unspecialized cellsthat renew themselves for long periods through cell division. The second is that under certain physiologic or experimental conditions, they can be induced to become cells with special functions suchas the beating cells of the heart muscle or the insulin-producing cells of the pancreas.
Scientists primarily work with two kinds of stem cells from animals and humans: embryonic stem cells and adultstem cells, which have different functions and characteristics.
Stem cells are important for living organisms for many reasons. In the 3- to 5-day-old embryo, called a blastocyst, stem cells indeveloping tissues give rise to the multiple specialized cell types that make up the heart, lung, skin, and other tissues. In some adult tissues, such as bone marrow, muscle, and brain, discretepopulations of adult stem cells generate replacements for cells that are lost through normal wear and tear, injury, or disease.
It has been hypothesized by scientists that stem cells may, at some point inthe future, become the basis for treating diseases such as Parkinson's disease, diabetes, and heart disease.
Properties of all stem cells
Stem cells differ from other kinds of cells in thebody. All stem cells—regardless of their source—have three general properties: they are capable of dividing and renewing themselves for long periods; they are unspecialized; and they can give rise tospecialized cell types.
Stem cells are unspecialized. One of the fundamental properties of a stem cell is that it does not have any tissue-specific structures that allow it to perform specializedfunctions.
Stem cells are capable of dividing and renewing themselves for long periods. Unlike muscle cells, blood cells, or nerve cells—which do not normally replicate themselves—stem cells may...