Stem cells are a large focus of study in today’s biomedical world. They are cells that exist in an undifferentiated state, and transform into different tissue types depending on what the cells surrounding them are. The different types of stem cells have the ability to repair many classes of damaged human tissue. Research in human developmental biology has led to the discovery of human stem cells (precursor cells that can give rise to multiple tissue types). There are two primary sources of stem cells, embryonic stem cells (ESC) and adult stem cells (ASC). Each of these types of cells has different characteristics as to how many different developmental paths they can follow and how much they can contribute to our understanding of a functioning organism. Only one type of stem cell, though, promises to regenerate virtually to any class of tissue. This is the highly controversial ESC, derived from very early embryos. They have particular promise for a wide range of therapeutic application because, according to our present knowledge, they are capable of giving rise to any cell type. In order to develop an opinion on whether or not stem cells should be used, one must first understand what they are and how they are used. Simply stated, the definition of a stem cell is an undifferentiated cell, meaning that it has no true function yet. However, all of the genes within a human stem cell have the potential to become other types of cells. The triggering mechanism for this cellular change is for the stem cells to be placed among specialized cells. Specialized cells include skin cells, muscle cells, or any other type of cell that has a specific function in the body. This paper will discuss the importance of stem cell research that can potentially help treat a range of medical problems such as multiple scleroses, Parkinson’s disease, Alzheimer’s disease, heart diseases, stroke, diabetes type1, birth defects, spinal cord injuries, cancer, burn injuries, and the ethical issues surrounding and limiting cell research.
Embryonic stem cells are derived from a four or five day old human embryo that is in the blastocyst phase of development. The embryos are usually extras that have been created in in- vitro fertilization (IVF) clinics where several eggs are fertilized in a test tube, but only one is implanted into a woman. Sexual reproduction begins when a male's sperm fertilizes a female's ovum (egg) to form a single cell called a zygote. The single zygote cell then begins a series of divisions, forming 2, 4, 8, 16 or more cells. After four to six days before implantation in the uterus, this mass of cells is called a blastocyst. The blastocyst consists of an inner cell mass (embryoblast) and an outer cell mass (trophoblast). The outer cell mass becomes part of the placenta, and the inner cell mass is the group of cells that will differentiate to become all the structures of an adult organism. This latter mass is the source of embryonic stem cells - totipotent cells (cells with total potential to develop into any cell in the body).
In a normal pregnancy, the blastocyst stage continues until implantation of the embryo in the uterus, at which point the embryo is referred to as a fetus. This usually occurs by the end of the 10th week of gestation after all major organs of the body have been created. However, when extracting embryonic stem cells, the blastocyst stage signals when to isolate stem cells by placing the "inner cell mass" of the blastocyst into a culture dish containing a nutrient-rich broth. Lacking the necessary stimulation to differentiate, they begin to divide and replicate while maintaining their ability to become any cell type in the human body. Eventually, these undifferentiated cells can be stimulated to create specialized cells. Embryos are also created