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does the human body know when to produce red blood cells or how to fight infection? Isn’t it amazing that all of the organs work together to equip a healthy body with all the essentials needed to live? How does that body accomplish this mission? It follows the human recipe. The human body can be so complex. We have 206 bones, 65,000 miles of blood vessels, bundles of nerves, numerous lymph nodes, and millions of red blood cells. Each has a specific job to do and every system is important to the body. Without our bones, we could not stand erect nor have structure and basically be like an earthworm! If our blood vessels become blocked, they cannot carry oxygen rich red blood cells that let us both breathe and think. We need our lymph system to help us combat infections and diseases. If we want to look deep inside the body to see how it works, we must start with the cell. The cell is very complicated indeed. It is very important to understand the nucleus, which is the main unit of the cell. The DNA is contained within the nucleus. DNA or deoxyribonucleic acid is what tells your body what color your eyes will be or what your fingerprints will look like. DNA has been described as looking like spaghetti. The cell uses a “fork” and twirls the DNA on to it. When the DNA is in this shape, it is called a chromosome. The DNA from one cell, if stretched, would be the height of a tall man. If you could unravel the entire DNA from all of the cells in your body, the strand would stretch from the Earth to the moon 6000 times! DNA forms a shape called a double helix. It resembles a spiral staircase. The staircase itself is made of carbon, hydrogen, oxygen, nitrogen, and phosphorus. The bases or “steps” are made of thiamine (T), adenine (A), cytosine(C), and guanine (G). When you write down a recipe, you need to make sure you have the ingredients in the right order and that the spelling is correct. If you follow the recipe's instructions exactly, you will have the same desired result every time. This is true for DNA. With only four base letters, A, T, G, and C, your body has the ability to combine the four-letter DNA alphabet in numerous configurations to produce desirable results every time. It is important to remember though, that everyone does not always follow the recipe nor is everyone a good cook. Most times when recipes are not followed exactly, your results are not as pleasing as you would have liked them to be. This is what can happen when ionizing radiation hits DNA. Normally, the DNA follows a recipe when it replicates or divides. The DNA carries the genetic information and makes an exact copy of it every time. This would be a desirable product. But, when radiation breaks through a part of the DNA strand or the whole strand, the recipe becomes altered. This is called a mutation. The DNA, now mutated, keeps dividing and makes an exact copy of this mutation every time it divides. The final outcome could be undesirable. Are mutations always undesirable? No. There are three categories of mutations. The first category is a neutral mutation. Cells may undergo a mutation where the change is not noticeable. An example of this would be when radiation interacts with a mature red blood cell. Red blood cells have a life span of 120 days. Mature cells do not divide. Therefore, if radiation were to interact with a cell that was near the end of its life span, it would not be actively dividing due to its age. More than likely, it would die; therefore, the mutation would not be duplicated. The second category is defined as a harmful mutation. An example of this would be when a mutation occurs with an immature red blood cell. The immature cell divides, replicates, and passes along the mutation. When immature cells interact with radiation, sometimes the mutations can lead to diseases such as cancer. The current estimate of the risk of dying from a radiation induced cancer is .05% per rad. This means that if one million people were exposed to 1 rad, an additional 500 deaths due to radiation-induced cancer would be predicted. The third category is defined as a helpful mutation. An example of this is found in people that live in a community near Milan, Italy. Their bodies are actually resistant to heart disease due to a mutation. They don’t have to count calories or watch their fat intake! How lucky is that? There are cells that are more sensitive to radiation than others. The cells that are immature and are rapidly dividing, undergoing mitosis, are the most susceptible to radiation mutations. The following is a list of cells in order of sensitivity with the most sensitive being listed first: 1. Lymphoid cells (found in the spleen, liver, and lymph nodes) 2. The reproductive cells (in males, spermatogonia, in females, the ovum) 3. Bone marrow cells (stem cells that give rise to all circulating blood cells and platelets) 4. Epithelial cells of the intestines (the gastrointestinal tract) 5. The epidermis (outer layer of skin) 6. Hepatic cells (cells of the liver) 7. The epithelium of the lungs 8. Kidney tissue 9. Cells of the intestinal cavity 10. Nerve cells 11. Bone cells 12. Muscle and connective tissue Every system follows its’ own recipe. Certain cells are more susceptible to a change in the recipe than more mature cells. Yet, as you can see, it is very important that the body follows the intricate human recipe so that all systems perform together to provide a healthy body. |
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