AQA A Level Biology复习笔记8.2.10 Two Types of Tumours

• Tumours are groups of abnormal cells that form lumps or growths
• They can start in any of the cells in our bodies
• Tumours have different characteristics depending on whether they are cancerous (malignant) or non-cancerous (benign)
• All tumours may cause harm to the body by:
  • Damaging the organ in which the tumour is located
  • Causing blockages or obstructions
  • Damaging other organs by exerting pressure

   

Malignant tumours

• Malignant tumours are cancerous
• Malignant tumours cause cancer by growing rapidly, then invading and destroying surrounding tissues
• Cells within malignant tumours secret chemicals that cause the formation of blood vessels to supply the tumour with nutrients, growth factors and oxygen
• Cells can break off these tumours and spread to other parts of the body through the bloodstream or lymphatic system, this is called metastasis
• Metastasis causes the spread of tumours to other places in the body, affecting multiple organs
• When removed through surgery, malignant tumours can still grow back
• The formation of malignant tumours can be initiated by carcinogens such as:
  • UV or X-ray exposure
  • Tobacco from cigarettes
  • Asbestos
  • Processed meat

   

Benign tumours

• Benign tumours are not cancerous
• These tumours grow slowly
• Benign tumours do not invade other tissues and do not metastasise, unlike malignant tumours
• These tumours can cause damage such as blockages or by exerting pressure on the organ it is growing in or those surrounding it
• When removed, benign tumours do not usually grow back
• The formation of benign tumours can be initiated by:
  • Inflammation or infection
  • Injury
  • Diet
  • Genetics
  • Toxins and radiation

   

• Examples of benign tumours are:
  • Polyps found in the nose, colon and ovaries
  • Non-cancerous brain tumours
  • Warts, caused by a viral infection