cancer 2.2.7

• a tumour is a mass of abnormally growing cells that form when the cells do not respond to the normal mechanisms that control the cell cycle, resulting in uncontrolled cell divisions
• cells usually divide slower with longer non-dividing time between each division - mitosis
• when a tumour forms, cells divide rapidly with very little non-dividing time for growth between each division
• benign tumours are not cancerous and are contained within a membrane in one place
• benign tumours grow very large, very quickly and can cause pressure on organs and be life threatening for example, benign tumours on the brain
• malignant tumours are cancerous and spread round the body, invading healthy tissues
• malignant tumours release small clumps of cells into the bloodstream that live longer and divide rapidly
• malignant tumours disrupt organs and tissues completely and can kill the host if untreated, however it is hard to treat as they move all around the body
• cancer can be inherited as there are genetic risk factors that can be inherited - this means if you inherit the gene you are more likely to develop that cancer, such as breast cancer or ovarian cancer
• carcinogenic chemicals such as asbestos and tar from cigarette smoke can cause mutations in genetic material and then cancer such as lung cancer
• ionising radiation such as UV light and x rays cam interrupt the normal cell cycle and can cause tumours because they cause mutations such as skin cancer
• some viruses can also cause cancer by disrupting the normal cell cycle such as HPV and cervical cancer
• there are so many different types of cancer because each one has a different causal mechanism
• a mutation is a change in the genetic material of an organism and could switch genes on and off and disrupt the normal mechanisms that control the cell cycle
• ionising radiation penetrates the cells and damages the chromosomes, causing mutations in the DNA
• the more you are exposed to ionising radiation, the more likely it is that mutations will occur and cancer will develop
• sunlight and tanning beds are a source of ultraviolet and increase the risk of skin cancers such as melanomas
• soil, water and air are sources of radioactive material which includes radon gas found in granite rich areas
• hospitals and dental surgeries are sources of x-rays
• accidents in nuclear power stations and testing nuclear weapons can cause radioactive waste which can spread over a large area
• radiotherapy is used to treat cancer by using targeted doses of radiation to destroy cancer cells
• chemotherapy is used to treat cancer by using chemicals to stop the cancer cells dividing or to make the cancer cells self destruct
• hair, skin, blood and stomach lining cells are damaged by the drugs used to treat cancer because the drugs also damage the healthier cells and prevent mitosis from occurring, they also grow quicker than the other cells in the body so are more likely to be affected
• to spot and prevent cancer early, check for any changes in the body, wear suncream, dont smoke, reduce obesity, store radioactive waste appropriately and fit radon alarms to houses