Stem cells

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Stem cells can divide and renew for long periods, are not specialized and can give rise to other specialized types of cells.
 

· In some adult tissues, such as bone marrow, muscle andbrain, small groups of adult stem cells can migrate and replace lost cells in various organs as a result of wear and tear, injury or illness.

All the people know that some cells (like the sperm cell andthe ovum) have the potential to form a complete organism, the first cells to arise from a fertilized ovum are described as totipotent.
 
Totipotent stem cells can grow into a complete organism,both the embryonic components and the extraembryonic (such as the placenta). That is, can form all the cell types.
After a few days in the womb, the blastocyst forms. The cells contained in it arecalled embryonic stem cells. However, a whole human cannot arise from these few cells. They have lost their toti-virility and are described as pluripotent.
 
Pluripotent stem cells are more restrictedcapacity; produce most of the tissues of an organism.
Adult stem cells have been in the skin, the brain, the blood, the liver and the bone marrow. These units are describes as multipotent cells.
 Multipotent stem cells are those cells can be generated only in its own layer of embryonic origin or ancestry.They also called organ-specific stem cells are capable of generating cells of a specificorgan in the embryo and in adults.
Our erythrocytes only live for about 120 to 130 days, by which time they have become too old, cannot transport enough oxygen and have to be replaced. These tasks istaken over by the hematopoietic stem cells of bone marrow, the most popular and are able to produce precursors of any type of blood cell.

The gradual differentiation of the progeny of stem cellsdepends on the combination of genetics and environmental factors. Also these cells are considered multipotent.
In the spinal cord, but also in umbilical cord blood, peripheral blood and in body fat...