- Embryonic stem cells are harvested from the blastocyst of a four to five day old human embryo. An embryonic stem cell consists of an inner cell mass (ICM, embryoblast) and an outer cell mass (trophoblast), forming the embryo and placenta respectively after implantation to the uterus. Adult or somatic stem cells exist in the body after embryonic development, to maintain and repair the tissue where they are found.
- Different characteristics of embryonic and adult stem cells
|Embryonic stem cells||Adult stem cells|
|Cell culture||Embryonic stem cells can be grown and harvested easily in culture with a well controlled environment.||The culturing methods of adult stem cells are not well developed.|
|Transplantation, rejection||There is a possibily of rejection due to the difference in the genetic makeup of the embryo stem cells and the recipient.||Rejection is less likely: patient's own cell is cultured and differentiated into specific cell types. Rejection still occurs if the genetic makeup of donor cells is different from recipient cells.|
- B. We understand the roles of stem cells in this unit. Scientists have revealed the function of stem cells extensively (Not A). Cells in the pancreas produce insulin (Not C). White blood cells fight against infection (Not D).