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What are Embryonic Stem Cells?

When the sperm fertilizes the egg, a zygote is formed. Then, the zygote goes through mitosis and splits into many cells, which themselves keeps splitting the zygote; that group of cells is referred to as the morula . In Figure 2.1 you can see that the original Zygote has split several times. Once the morula reaches about 16 cells, which takes about 4-5 days, the cells start differentiating from one another and the cells begin to form an outer layer, the outer cells are called trophoblast while the inner cells are called the embryoblast . After this, fluid will start filling in between the embryoblast and trophoblast, fluids are going to fill the gaps between the inner cells and outer cells. The process of mitosis continues, the outers cells duplicate as do the inner cells. The fluid that comes between the embryoblast and trophoblast is referred to as the blastocoel . This group of cells, including the blastocoel, is called the blastocyst . In Figure 3.1 we can see the the steps a zygote takes to become the blastocyst.The embryoblast is what will eventually turn into the organism and the trophoblast will turn into the placenta. The placenta is where the human embryo develops. All of the cells located inside of the placenta have the potential to develop into different types of cells. For instance, one of these cells might turn into a muscle cell while another cell might develop into a nerve cell. These cells are called embryonic stem cells .

The embryonic stem cells will develop in a certain way depending on what type of environment they are kept in. In research laboratories the embryonic stem cells are experimented with in order to turn them into cures for diseases; such as cancer. For example if an embryonic stem cell is placed in a damaged muscle cell, the embryonic stem cell will develop into a muscle cell to repair the damage.


Use of Embryonic Stem Cells

Embryonic stem cells are usually experimented with and developed In Vitro fertilization. This is where scientists and researchers will take eggs from a mother, who is usually unable to have children. Then, they fertilize the eggs with sperm, which usually comes from sperm donors, meaning that these eggs evolve into zygotes. These zygotes are then developed into blastocysts. The researchers and scientists observe each of the embryos in the blastocysts and see which ones are healthy, which ones might become into humans or not.Also embryonic stem cells can continue to endlessly duplicate themselves. This is a great benefactor as many embryonic stem cells can be used for research and treating illnesses. Scientists have suggested that embryonic stem cells be used for treating damaged tissue in order to regenerate it. The healthy embryos are implanted back into the mother, while many of the other embryos are thrown away, frozen, or destroyed.

There has been a debate going on regarding the use of embryonic stem cells. The embryonic stem cells are derived from embryos, which has a potential of developing and growing into a human being, which means that using these stem cells is killing potential human beings. However, others say that embryonic stem cells can be used to fight diseases and save lives, as these cells can turn into any type of cell.

The Three Different Germ Layers

There are three different germ layers, which are different tissue types that embryos can develop into. The three different layers are ectoderms , mesoderm , and endoderm .

Ectoderm- This is one of the three germ layers, specifically these tissue types are usually found in the outer cells of the embryo. These outer cells will develop into skin, the nervous system, tooth enamel, sensory organs, and eye lens.

Mesoderm- Another one of the germ layers, this type is found in the middle layer cells of the embryo and it will develop into muscle, bone, blood, connective tissues, and kidneys.

Endoderm- These are found in the inner layer of the embryo and they will develop into digestive organs, lungs, the pancreas, and the liver.


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