In adults, where are stem cells primarily found?

Stem cells in adults are primarily found in the liver and bone marrow because these areas are crucial for the regeneration and repair of tissues. Bone marrow is particularly important as it contains hematopoietic stem cells, which give rise to all types of blood cells, playing a vital role in maintaining healthy blood and immune system function. The liver also has a regenerative capacity and contains liver stem cells, which can contribute to the maintenance and repair of liver tissue following injury or disease.

In contrast, while other tissues like skin and the brain do contain stem cells, the concentrations and types of stem cells found there are not as significant or prevalent as those found in the liver and bone marrow. The heart and lungs do not typically house stem cells in the same way that the liver and bone marrow do, and while stem cells are present in the eyes and ears, they are less central to the primary functions of regeneration in these organs compared to those found in the liver and bone marrow.