Ever since we were born, very few of our cells remained the same, and they are mostly neurons (nerve cells). Otherwise, the rest of the cells are in a continuous state of death and division. This has to be tightly controlled to avoid decreased or increased number of cells in a given tissue, and those control mechanisms are also dependent on the state of the body and its need for new cells of a specific type. This is what makes the human body so complex.
The main key to such complexity is our DNA, the blueprint of our bodies. If our DNA is altered, and several repair mechanisms fail to fix the defect, our cell also has other self-destruct mechanisms to avoid harm. If all the previous defense mechanisms fail at the same time, cancers can develop.
What is the bone marrow?
If our blood cells were to be manufactured products, the bone marrow would be the manufacturing plant, and raw materials are called stem cells. These stem cells differentiate into the different cells floating in our blood stream, namely red blood cells -or corpuscles to be more precise-, white blood cells and platelets.
The bone marrow is located within the cavities of long bones as those of your thighs and arms as well as bones of the axial skeleton including the ribs, skull and the hip bones. If you ever tasted or saw marrow of cattle, you’ll notice that it is very greasy and mainly has fat in it. That is because starting from childhood and until adulthood, the red bone marrow is replaced by fat cells, and by late adulthood the active or red marrow is only found in the thighs, hip bone and perhaps the breastbone, or “sternum”.