What is it?
- Cancer is a term used for diseases in which abnormal cells divide without control and are able to invade other tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems
- It is not a singular disease; there are more than a hundred different types of cancer and most cancers are named for the organ or type of cell in which they start
- We can group cancers into larger categories, however. There is carcinoma, cancer that begins in the skin or tissues that line and cover internal organs, sarcoma, cancer that beings in bone, cartilage, fat, muscle, blood vessels and other connective or supportive tissue, lymphoma and myeloma, cancer that begins in the cells of the immune system and central nervous system cancers, that begin in the tissues of the brain and spinal cord.
To first understand it, it is best to be familiar with what a cell looks like and how cell division works, so here are some diagrams below to explain it:
- The origins of cancer starts with cells becoming cancerous cells. This occurs as a result of damage to a healthy cell. The DNA is copied and the cell checks if the DNA has been copied correctly and usually a cell with damaged DNA will die. However, sometimes the cell ignores this warning and continues to multiply. When a cell is dividing, it creates something called spindles that attached to the DNA at both ends in the cell, and the cell once again checks if the DNA has been copied correctly. So usually, a cell with a faulty spindle attachment will die. However, sometimes the cell will divide anyway. When the cell splits, each new cell do not have the same number of chromosomes (due to the DNA damage) and this this means some cells do not have the correct number of genes and other cells have extra copies. As these faulty cells no longer have the correct 'instructions' they will multiply out of control.
- Genes are what tells the cell how to behave. Different genes tell the cell how to make different proteins and proteins are what makes the cell - it is the building block of cells if you will. Some proteins act as on and off switches that help to control how a cell behaves, e,g, a hormone signal acts on a protein in or on the cell. The protein then sends a series of signals which tell the cell to reproduce by dividing into two. Cells communicate with one another using chemical signals produced in the body which attach to receptors on the cells. This triggers a flow of signals sending a message to the nucleus to what genes should be turned on and off - whether to divide or self-destruct. Cell signalling goes wrong in cancer - too many signals can be sent or not get through at all
- A mutation, then, in contrast, means that the gene has been damaged or lost and so the protein may be made in too much quantity or not at all. Consequently, a signalling protein may be continuously switched on or cells that control cell division switched off.
- Abnormal genes in cancer: oncogenes (encourages the cell to multiply), tumour suppressor genes (stops the cell multiplying), DNA repair genes (repairs other damaged genes)
- Something that damages a cell and makes it more likely to be cancerous is called a carcinogen
- Mutations happen by chance when a cell is reproducing - it is at random. However, some people are said to be genetically predisposed to a type of cancer as they are born with with one of the mutations that'll make a cell cancerous (more than one mutation is needed for it to develop into a cancer, however)
- A tumour is a lump in the body formed from these abnormal cells and are classed as benign or malignant, Benign tumours are not cancerous and usually not life threatening. Malignant tumours, on the other hand, its cells can spread into blood vessels and to other parts of the body, therefore creating secondary tumours.
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