Cancer
Cancer is a disease in which the cells in the body grow in an uncontrollable fashion and spread to other parts of the body. Cancerous tumors spread and invade the surrounding tissues and can travel to distant places in the body to form new tumors. This process is called metastasis. Cancerous tumors may also be called malignant tumors.
Differences Between a Cancerous Cell and a Normal Cell
- Cancerous cells grow in the absence of signals which instruct them to grow while normal cells only grow when they receive such instructions.
- Cancerous cells ignore signals that normally instruct cells to stop dividing or to die (apoptosis or programmed cell death) while normal cells stop dividing after receiving signals.
- Cancerous cells invade into surrounding areas and spread while normal cells stop growing when they come in contact with the other cells (contact inhibition).
Types of Tumors
Benign tumors |
Malignant tumors |
They are small |
They are large |
They are slow growing |
They are fast-growing |
They are non-invasive |
They are invasive |
They stay localized |
They are metastasized |
Causes of Cancer
The normal cells are transformed into cancerous cells through some agents, known as carcinogens.
Carcinogens
- Ionizing radiations: X-rays and gamma rays.
- Non-ionizing radiations: Both ionizing and non-ionizing radiations, cause DNA damage and mutations.
- Some food items like chemicals, used in processed and cured meat may produce carcinogens.
- The chemical carcinogens cause lung cancer, are present in tobacco smoke.
- Oncogenic viruses (cancer-causing viruses) consist of viral oncogenes.
Detection and Diagnosis
Cancer detection is done by:
- Biopsy: In this process, a small and thin section of the suspected tissue is taken out and examined.
- Blood and bone marrow tests: This is done to detect leukemia or blood cancer.
- Radiography: Here, X-rays are used to expose the infected cell.
- CT (computed tomography): This is done to obtain a 3-D structure of an infected organ through X-rays.
- MRI (magnetic resonance imaging): It involves the use of strong magnetic fields and non-ionizing radiations to detect the changes in the cells or tissues.
- Techniques of molecular biology: It is used to identify the genes which prevent cancers.
Treatment of Cancer
There are different ways to treat cancer like surgery, radiation therapy, chemotherapy, and immunotherapy. In radiotherapy, the tumor cells are exposed to the X-rays, taking care of the normal cells surrounding them. There are certain drugs used to kill or burn cancerous cells, known as chemotherapeutics. These drugs show some side effects like hair loss, anemia, excessive weight loss, etc.
NCERT Notes on Class 12 Biology Chapter 7 – Human Health and Disease
NCERT Chapter 7 of Class 12 Notes on Human Health and Disease: According to the World Health Organisation, health can be defined as a state of complete physical, mental, and social well-being and not merely the absence of disease and infirmity. Good health has many benefits like it helps to keep us happy. Our skin, teeth, and eyes remain healthy, support muscles, enhance immunity, strengthen bones, and lower the risk of heart ailments, diabetes, and some cancers. It also supports healthy pregnancies and breastfeeding among women.
NCERT Notes on Chapter 7 Human Health and Disease: On the other hand, disease is any undesirable change in our body that may keep us disturbed whether it is physical, mental, or social. Our body can undergo a number of changes like any of the organs can stop functioning in a proper way which can also be associated with some other signs and symptoms. In plants and animals, the disease can also be occurred by pathogens, i.e. disease-causing organisms such as fungi, bacteria, viruses, protozoa, and certain types of invertebrates like tapeworms, wuchereria. Unhygienic surroundings, nutritional deficiencies, and unhealthy lifestyles also cause diseases.