Discussion of all aspects of cellular structure, physiology and communication.
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Hello, I am well aware of the concepts of Stem Cells (Cell specialization) and Cell Division (Mitosis), however I am unsure of where their applications lie. I am well aware of the function of embryonic stem cells (As I know that Cell Specialization must occur in order for all our vitals and tissues to be formed). However, somatic (Adult tissue) stem cells I am unsure of. My question is, is that if our vitals and tissues are formed during our embryonic stages of development, then in theory, couldn't mitosis do the rest of the work in replacing these cells continuously, and keeping these tissues alive and functioning? Why must we have somatic stem cells? Can't mitosis be used to replace all dying cells? Basically in a nutshell, in what cases must Cell Specialization occur, and in what cases must Mitosis occur?
Cell division demands lot of resources in the form of energy. Therefore, it is easy to have dedicated cells for division and differentiation. Therefore, normal cells can continue doing their tissue function whereas adult stem cells perform their function i.e. dividing and replacing damaged cells.
Also, the question 'why?' seems to be unanswerable. This is the result of evolution. We must understand the origin and evolution of stem cells to understand at what junction during the course of evolution, a need for stem cells arose. Until then it might be a mystery.
The Biology Org
I. Stem cells are central to three processes in an organism: development, repair of adult tissue and cancer.
A. Stem cells in mammalian development
The zygote is the ultimate stem cell. It is totipotent with the ability to produce all the cell types of the species including the trophoblast and the embryonic membranes. Development begins when the zygote undergoes several successive cell divisions, each resulting in a doubling of the cell number and a reduction in the cell size. At the 32- to 64-cell stage each cell is called a blastomere.2 The blastomeres stick together to form a tight ball of cells called a morula. Each of these cells retains totipotential. The next stage is the blastocyst which consists of a hollow ball of cells; trophoblast cells along the periphery develop into the embryonic membranes and placenta while the inner cell mass develops into the fetus. Beyond the blastocyst stage, development is characterized by cell migration in addition to cell division. The gastrula is composed of three germ layers: the ectoderm, mesoderm and endoderm. The outer layer or ectoderm gives rise to the future nervous system and the epidermis (skin and associated organs such as hair and nails). The middle layer or mesoderm gives rise to the connective tissue, muscles, bones and blood, and the endoderm (inner layer) forms the gastrointestinal tract of the future mammal.
Early in embryogenesis, some cells migrate to the primitive gonad or genital ridge. These are the precursors to the gonad of the organism and are called germinal cells. These cells are not derived from any of the three germ layers but appear to be set aside earlier.
It's interesting that you have such confusions. I now haven't thoutht much about that. I'm wondering that may be thousands of years latter, not only humans, but animals as well don't need somatic stem cells any longer. We will see.
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