Like many other types of stem cells, mesenchymal stem cells are also capable of self-renewal. Mesenchymal stem cells develop into a number of specialized cells including chondrocytes, adipocytes, and osteoblasts among others. * Some hematopoietic stem cells have also been identified in blood.Īlso referred to as skeletal stem cells in some books, mesenchymal stem cells are not related to blood stem cells (hematopoietic stem cells) in adults.Īlthough they are, for the most part, found in the bone marrow, mesenchymal stem cells have also been identified in a number of other tissue including the liver and lung of the fetus, and cord blood among others. In addition to the ability to renew themselves (self-renewal), hematopoietic stem cells in the bone marrow also contribute to the entire spectrum of blood cells (red cells, white cells, platelets).īecause these help to produce only specific related cells (blood cells) they are described as multipotent stem cells. Hematopoietic stem cells only make up a small percentage of cells in the bone marrow (about 1 in 10,000 cells). As such, adult stem cells also contribute to homeostasis. However, they can still be found in various tissues where they serve to replace cells that die due to diseases or injuries. * In adults, stem cells are very few in number. * In some mature tissues, the origin of adult stem cells is yet to be fully understood. This makes it possible to replenish and regenerate tissues in cases where cells die or are damaged. Unlike embryonic stem cells located that are found/derived from a mass of cells of the blastocyst, adult stem cells can be found in different parts of the body. Various types of mature specialized cells that perform specific functions are developed. Like other stem cells, these are capable of self-renewal as they can make new copies of themselves (long term self-renewal). At this point, the inner cell mass that contains the embryonic stem cells (pluripotent cells) is fully formed.Īlso known as somatic stem cells, adult stem cells are a type found in children and adults. * The blastocyst is formed about the 5th day. At this stage, the embryo is capable of developing into a fully developed organism. * At about the third day of division (following fertilization), at the eight-cell stage the cells are totipotent. These are only present during the first stage of development. In particular, they are located within an inner cell mass of the blastocyst.īecause of their ability for self-renewal and the fact that they differentiate into every type of cell in the body, these stem cells significantly contribute to the growth and development of a fetus in the womb.
Skin cells are a good example of unipotent stem cells.īased on their sources, stem cells are widely divided into two main categories that include:Īs the name suggests, embryonic stem cells are the type of stem cells derived from embryos (4 to 5 days old). As such, unipotent stem cells have the lowest differentiation potential compared to other types of stem cells. Unipotent - Unipotent stem cells give rise to cells of their own type along a single lineage. Oligopotent stem cells - Stem cells like myeloid stem cells are referred to as oligopotent because they produce a few types of cells (e.g. Some of the other classifications include: Because these types of stem cells yield to very specific type of cells (closely related) they are found in many tissues in the body where they perform this function. Hematopoietic stem cells, for instance, can only produce red and white blood cells (including platelets).
As such, they do not differentiate into a wide variety of cells as is the case with totipotent and pluripotent stem cells. Multipotent - Multipotent stem cells are the type of stem cells that only produce closely related cells.
* Unlike the totipotent stem cells, pluripotent stem cells are located in the inner mass of the blastocyst. Compared to totipotent stem cells, pluripotent stem cells can only progress to cells from any of the three germ layers (mesoderm, endoderm, and ectoderm). Pluripotent - Examples of pluripotent stem cells include embryonic stem cells. * Totipotent stem cells are located in the early cells of a fertilized egg. These cells are characterized by high potency which means that they are capable of differentiating into any type of cell in an organism.įor instance, the zygote formed following fertilization of the egg gives rise to types of cells that form particular tissues and organs. Totipotent - A zygote is a good example of a totipotent stem cell. Whereas some stem cells are capable of generating more types of specialized cells (those with greater potency) others can only generate few specialized cells and thus have lower potency. With regards to stem cells, potency refers to their ability to differentiate into distinctive types of cells.