Stem cells have offered much hope by promising to greatly extend the numbers and range of patients who could benefit from transplants, and to provide cell replacement therapy to treat debilitating diseases such as diabetes, Parkinson's and Huntington's disease. The issue of stem cell research is politically charged, prompting biologists to begin engaging in ethical debates, Stem cell research offers great promise for understanding basic mechanisms of human development and differentiation, as well as the hope for new treatments. However, human stem cell research also raises sharp ethical and political controversies. This paper will discuss the types of stem cells as well as some of the controversies involved in stem cell research.
According to Wikipedia, stem cell can be defined as “biological cells found in all multicellular organisms, that can divide (through mitosis) and differentiate into diverse specialized cell types and can self-renew to produce more stem cells.” A stem cell could be regarded as one of the basic building blocks of the human body. Stem cells are important because they have the ability to become different cell types, and scientists are working on developing ways to use stem cells to repair or regenerate damaged organs or tissues. This could lead to therapies for a whole range of conditions such as heart disease, diabetes, Parkinson's disease or Alzheimer's, although at present it is impossible to tell whether this will happen within a few years or even within our lifetimes. Furthermore, Scientists also say that by studying stem cells they will learn more about reproductive and cell biology and can also use this knowledge for drugs testing and development. Although, there is some debate among scientists about this. Broadly speaking, there are three different types of stem cells: embryonic stem cells and adult stem cells (including stem cells derived from umbilical cord blood). These stem cells are found in animal as well as human tissue.
Types of Stem Cells
Stem cells are a class of undifferentiated cells that are able to differentiate into specialized cell types. Commonly, stem cells come from two main sources: embryonic stem cells and adult stem cells. Both types are generally characterized by their potency, or potential to differentiate into different cell types (such as skin, muscle, bone, etc.). Adult or somatic stem cells exist throughout the body after embryonic development and are found inside of different types of tissue. These stem cells have been found in tissues such as the brain, bone marrow, blood, blood vessels, skeletal muscles, skin, and the liver. They remain in a quiescent or non-dividing state for years until activated by disease or tissue injury. Adult stem cells can divide or self-renew indefinitely, enabling them to generate a range of cell types from the originating organ or even regenerate the entire original organ. It is generally thought that adult stem cells are limited in their ability to differentiate based on their tissue of origin, but there is some evidence to suggest that they can differentiate to become other cell types.
On the other hand, 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 IVF (in vitro fertilization) 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 cells, etc. 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...
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