Stem cells are cells that can not be differentiated. There are various sources in which stem cells occur; adult tissue and embryonic. Stem cells are mostly found in organisms which are multi-cellular. These cells are capable of renewing themselves. They undergo renewal through a process known as mitotic cell division. They differentiate in to cell types which are specialized. Till and Ernest are amongst the researchers who did much in the field of stem cells. There are two main types of stem cells in mammals; adult stem cells and embryonic cells (Weissman Irving, 2006). The embryonic stem cells are separated from blastocyst. On the other hand adult tissues consist of adult stem cells. Stem cells are capable of differentiating during embryo development. This occurs within the embryonic tissues. Stem cells perform various functions in adult tissues. This includes cell replenishment and body repair. They are also involved in the maintenance of regenerative organs. Such organs include; skin and blood. Stem cells can be changed to cells which are specialized. The cells are grown within adult tissues such as nerves. There are certain stem cells which originate from certain adult tissues which are used for carrying out medical therapies. Some of the sources of these stem cells include bone marrow. Potency is one of the major characteristics of the two types of stem cells. They are capable of differentiating to specialized cells.
Embryonic stem cells are cells which are not differentiated. The source of these cells is the inner cell mass. This is referred to as blastocysts. These cells are capable of renewing themselves. They remain pluripotent and maintain the karotype in them during renewal (Drummond Daniela, 2008). They can differentiate in to a couple of cell types. The cells formed take up the germ layers. Several researches have been carried out to identify the phenomenon of these cells. Such include injection of cells to mice. The creation of tumors occurred during the research. Tumors are comprised of several cell types.
The embryo of a young aged human acts as the source for embryonic stem cells. The ages in this cases ranges to a couple of days. The cells are derived when the embryo is in the blastocyst stage in the process of development. The embryos used for this purpose are brought up artificially using test tube. This is done through fertilization which takes place externally. In such a case, a couple of eggs are introduced to sperms for fertilization after which one is chosen for implantation in the uterus. Reproduction begins during fertilization ((Moulton Forest R., 1940). This is when the ovum meets the sperm. A zygote is formed during fertilization. A prose of divisions begins from the zygote cell. The cells formed range from two onwards. Blastocyst is the total number of cells formed before implantation is carried out within the female womb. This takes effect within a couple of days after fertilization. The blastocyst is comprised of trophoblast and embryoblast. Trophoblast consists of the outer cell mass while embryoblast consists of the inner cell mass. The placenta is formed from the outer cell mass. There are various structures which are found in adult organism. These structures are formed as a result of differentiation of the inner cell mass. Embryonic stem cells are derived from the cells concerned with formation of structures found in adult organism. These cells are totipotent meaning that they have the capacity of developing in to any of the cells found in the body. Fetus is a development stage of the embryo after implantation in the uterus. The main organs within the body are already formed during this stage. There is a procedure which is followed during extraction of the embryonic stem cells. The separation of the stem cells is determined by the blastocyst stage. During extraction of the stem cells the group of cells is placed in a culture dish. This culture dish is constituted with the essential nutrients for growth. These cells lack the essential stimulation leading to differentiation. This causes replication and division of the cells in to different cell types (Palay Sanford L., 1991). The ability to take any form of cell type is maintained. The researches which have been conducted to attest stems cells are taken from human cells or mice. Undifferentiated state is maintained differently in these two cases. The environments under which they are extracted are different. Leukemia inhibitory Factor is required in the extraction of stem cells from mice. On the other hand Fibroblast Growth Factor is required in the extraction of stem cells from human. Embryonic stem cells differentiate rapidly when there is no genetic manipulation. There are several ways in which embryonic stem cells can be identified in humans. This includes the presence of surface proteins in cell and transcription factors.
There are various ways in which stem cells can be extracted. They can be extracted within the culture dish, a time when the zygote is in the process of division. They can also be derived from adult tissue. The extracted cells are then placed in a culture which is controlled. The controlled cells are only capable of replicating and dividing but not specializing. Specialization of cells is prohibited by the controlled environment.
The cell which is capable of dividing to form another different cell and is found within a developed organism is referred to as adult stem cell (Prentice David A., 2004). The cell has the ability to create a different cell than itself. Somatic is another term used to refer to adult stem cell. Stem cells are found in adults and also in children. There are some stem cells that are pluripotent. These occur in small numbers and within certain tissues. Some of the tissues which have such cells include blood of umbilical cord. Adult stem cells are classified according to their ability for self renewal and division. Stem cells in mice make them live for a short period of time.
The tissues under which adult stem cells are derived define the stem cells. There are various treatments which have been achieved as a result of treatment of stem cells. Such treatments include; leukemia. Cell division occurs in stem cells to acquire the property of self renewal. There are various types of division which enable self renewal; asymmetric and symmetric division. Two daughter cells which are the same occur in the case of symmetric division. A single stem cell occurs for the case of asymmetric division. The self renewal ability of such cell is limited. Some of the cells undergo a couple of division before differentiation takes place. Differential segregation denotes the difference between asymmetric and symmetric division.
In conclusion, stem cells are cells which have the capability of self renewal and differentiation. They occur in both adult and children. Stems cells can be categorized in to two major categories; adult stem cell and embryonic cells. Embryonic stem cells occur during blastocyst stage in embryo. The embryo is developed after fertilization which involves fusion of the ovum and sperm. There are various ways of extracting stem cells; from culture dish and the body tissues.