Embryonic stem cells : are derived from embryos. Most embryonic stem cells are derived from embryos that develop from eggs that have been fertilized in vitro. The embryos from which human embryonic stem cells are derived are typically four or five days old and are a hollow microscopic ball of cells called the blastocyst. The blastocyst includes three structures: the trophoblast, which is the layer of cells that surrounds the blastocoel, a hollow cavity inside the blastocyst; and the inner cell mass, which is a group of cells at one end of the blastocoel that develop into the embry o proper.
Chief characteristics of stem cells : Embry onic stem cells differ from other kinds of cells in the body.
Embryonic stem cells have three general properties:
1. they are capable of dividing and renewing themselves for long periods;
2. they are unspecialized; and
3. they can give rise to specialized cell types.
Embryonic 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- Embiyonic stem cells may replicate many times, or proliferate. Embryonic 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 specialized functions. For example, a stem cell cannot work with its neighbors to pump blood through the body (like a heart muscle cell), and it cannot carry oxygen molecules through the bloodstream (like a red blood cell). Embryonic stem cells, can give rise to specialized cells, including heart muscle cells, blood cells, or nerve cells.
Uses of Embryonic stem cells: Studies of human embryonic stem cells will yield information about the complex events that occur during human development. A primary goal of this work is to identify how undifferentiated stem cells become the differentiated cells that form the tissues and organs.
Embryonic stem cells could also be used to test new drugs.
For example, new medications could be tested for safety on differentiated cells generated from human pluripotent cell lines. Perhaps the most important potential application of human embryonic stem cells is the generation of cells and tissues that could be used for cell-based therapies.