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Teacher Background Cell Growth and Differentiation "Human development begins when a sperm fertilizes an egg and creates a single cell that has the potential to form an entire organism. In the first hours after fertilization, this cell divides into identical cells. Approximately four days after fertilization, and after several cycles of cell division, these cells begin to specialize, forming a hollow sphere of cells, called a blastocyst. The blastocyst has an outer layer of cells and inside this hollow sphere there is a cluster of cells called the inner cell mass. The inner cell mass cells will go on to form virtually all of the tissues of the human body. Although the inner cell mass cells can form virtually every type of cell found in the human body, they cannot form an organism. Therefore, these cells are referred to as pluripotent, that is, they can give rise to many types of cells but not a whole organism. Pluripotent stem cells undergo further specialization into stem cells that are committed to give rise to cells that have a particular function. Examples include blood stem cells that give rise to red blood cells, white blood cells and platelets and skin stem cells that give rise to the various types of skin cells. These more specialized stem cells are called multipotent-capable of giving rise to several kinds of cells, tissues, or structures." (1)
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National Center for Biotechnology Information | ||||
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