What are embryonic stem cells and how do they differ from adult stem cells?
Embryonic stem cells, also known as early stem cells, are present in the inner cell mass of blastocyst after around five days of development. They are pluripotent cells that can differentiate into any tissue of the body and are considered possibly immortal.
Adult stem cells, precisely called somatic stem cells, are undifferentiated multipotent or totipotent cells found in mature body tissues, the umbilical cord, and placenta. Their primary role is to preserve and repair the tissue in which they reside. A key difference is that embryonic stem cells face ethical dilemmas and safety issues regarding their use, whereas adult stem cells do not. Additionally, while embryonic stem cells can become any tissue, adult stem cells were thought to be dedicated to a specific lineage, though they now show plasticity.
Explanation
The answer is derived directly from the provided textbook context. It defines embryonic stem cells based on their origin (inner cell mass of blastocyst) and potency (pluripotent). It defines adult stem cells based on their location (mature tissues, umbilical cord) and function (repair and preservation). The comparison highlights the differences in potency, ethical considerations, and the concept of plasticity mentioned in the text.