Cancer is a term used to describe a large array of illnesses all having certain common characteristics. The main feature that all cancers have in common is the unregulated control of cell growth, resulting in serious health problems. There are over 200 different types of cancer, and each has a specific name and treatment. In order to understand what cancer is, it is first necessary to briefly describe how normal cells grow.
Many different organs perform the vital functions of the human body .
For example the lungs provides oxygen for respiration, the stomach digests food and the heart-muscle contracts to pump blood around the body. Each of these organs is made up of many different types of cells, and each cell has a particular function within that organ. For example, in the heart, specific cells called cardiac muscle-cells pump blood. However, other types of cells are also located in the heart, for e xample cardiac nerve cells. These cardiac nerve cells are needed to conduct the electrical signals to produce each contraction.