8. HUMAN HEALTH AND
DISEASES
CANCER
·
Cancer is an abnormal and
uncontrolled multiplication of cells resulting in the formation of tumour (masses
of cells).
·
Normal cells show a contact
inhibition (contact with the other cells inhibits their uncontrolled
growth). Cancer cells do not have this property.
Types of Tumours
o Benign tumours: Confined
to the place of its origin. They do not spread to other parts.
Cause little damage.
o Malignant
tumours: Mass of
proliferating
cells (neoplastic or tumour cells) that grow rapidly, invade and damage
the surrounding normal tissues. Due to active division and growth, they starve normal cells by competing for
nutrients.
Cells sloughed from tumours
reach other sites via blood where they form a new tumour. This is called metastasis.
Causes of cancer (Carcinogens)
§ Physical agents:
E.g. Ionizing radiations like X-rays and gamma rays and non-ionizing radiations
like UV.
§ Chemical agents:
Tobacco smoke (major cause of lung cancer), vinyl chloride, caffeine, nicotine, mustard gas etc.
§ Biological agents: E.g.
oncogenic viruses, c-onc (cellular oncogenes
or proto oncogenes) etc.
When C-onc in normal cells is activated, the cells become oncogenic.
Cancer detection and diagnosis
o Biopsy:
A thin piece of the suspected tissue is stained and examined under microscope
(histopathological studies).
In case of
leukemia: Biopsy & histopathological studies. Blood & bone marrow tests for increased cell
counts.
o
Imaging
techniques:
§
Radiography:
Use of X-rays.
§
CT
(Computerized tomography) scan: Uses X-rays to generate a 3D image of the
internals of an object.
§
MRI
(Magnetic Resonance Imaging): Uses magnetic fields and non-ionising radiations to detect pathological
and physiological changes in the living tissue.
o Use
of Antibodies against
cancer-specific antigens.
o Molecular biology
technique: To detect cancer related
genes. Such individuals should avoid carcinogens (e.g. tobacco smoke).
Treatment of cancer
o Radiotherapy: Tumour
cells are irradiated lethally, without damaging surrounding normal tissues.
o Chemotherapy: Use
of chemotherapeutic drugs. Many drugs have side effects like hair loss, anaemia
etc.
o Immunotherapy: The
patients are given biological response
modifiers (e.g. α- interferon) which activates their immune system and
helps in destroying the tumour.
o
Surgery.
Most cancers are treated by combination of surgery, radiotherapy and chemotherapy.