Biology HUMAN HEALTH AND DISEASE

Cancer

Cancer is one of the most dreaded diseases of human beings and is a major cause of death all over the globe. More than a million Indians suffer from cancer and a large number of them die from it annually. The mechanisms that underlie development of cancer or oncogenic transformation of cells, its treatment and control have been some of the most intense areas of research in biology and medicine.

- Uncontrolled, Abnormal and excessive mitotic division of cells is called cancer (Crab = cancer).
- Study of cancer is called oncology
- This abnormal and undifferentiated cells are called cancerous cells.

TUMOUR OR NEOPLASM (New growth)

(a) Benign Tumour: capsulated, localised to the site of origin & does not spread to another parts of body, it is non
metastatic, non-malignant, non-cancerous, Non invasive
eg.
- Bone tumour - Osteoma
- Muscle tumour - Myoma
- Lymph node tumour - Lymphoma

(b) Malignant Tumour (Malignant = Harmful) : Some of the cancerous cells detach from their origin place and spread to other parts of body by blood and lymph. Now the cancerous cells form fresh colonies there. This is called metastasis or sec. growth. 'TI1is type of tumour is called metastatic or cancerous tumour. It is Invasive tumour.
e.g. All malignant tumour are called cancers.

In our body, cell growth and differentiation is highly controlled and regulated. In cancer cells, there is breakdown of these regulatory mechanisms. Normal cells show a property called contact inhibition by virtue of which contact with other cells inhibits their uncontrolled growth. Cancer cells appears to have lost his property. As a result of this, cancerous cells just continue to divide giving rise to masses of cells called tumors. Tumors are of two types : benign and malignant. Benign tumors normally remain confined to their original location and do not spread to other parts of the body and cause little damage. The malignant tumors, on the other hand are a mass of proliferating cells called neoplastic or tumor cells. These cells grow very rapidly, invading and damaging the surrounding normal tissues. As these cells actively divide and grow they also starve the normal cells by competing for vital nutreients. Cells sloughed from such tumors reach distant sites through blood, and wherever they get lodged int he body, they start a new tumor there. This roperty called metastasis is the most feared property of malignant tumors.

CANCER IS DIVIDED INTO 3 CLASSES ON BASIS OF ORIGIN

(i) Carcinoma : This tumour originate from the Skin and epithelial tissue eg :
(a) Brain carcinoma
(b) Oral carcinoma
(c) Gastric carcinoma
(e) Lung carcinoma
(g) Adena carcinona (gland tumour)
(d) Colon carcinoma
(f) Cervical carcinoma
(h) Breast carcinoma

- Carcinoma is most common type of tumour (85%)
- Breast cancer in female and prostate cancer in males are common incidence in world. Lung cancer accounts for 31.1% of all cancer death in men and 25% in women.
- Cervical (Uterine Cervix) cancer in females and oral cancer in males are common in India.
- Melanoma - It is type of carcinomas. These are cancerous growths of melanocytes (a type of skin cells).

(ii) SARCOMA :
This is tumour of mesodermal tissue( 1%).
eg.
Bone cancer - Osteosarcoma
Muscle cancer - Myosarcoma
Lymph node cancer - Lymphosarcoma.

(iii) Leukaemia (Leucocyte = W.B.C.) or Blood Cancer : This is cancer of white blood cells (WBC).
a. Chronic Myelogenous Leukaemia (CML) : This fatal cancer occurs mainly due to reciprocal translocation
between chromosome-22 (Philadelphia chromosome) and chromosome 9.
b. Burkitt's Lymphoma : This is a type of leukaemia which is produced due to reciprocal translocation between chromosome-S and chromosome-14.
According to a rough estimate about 8 lacs cases of cancer are detected in India every year out of which 4 lakhs succumb to daeth.

Normal mechanism of body growth -

Normal cell division regulation by proto-oncogens and it is suppressed by tumour suppressor gene.
Chemical or physical agents that can cause cancer are known as carcinogen. Depending on their mode of action, carcinogens fall into the following main categories:
(i) Agents that can cause alterations in the genetic material (DNA), resulting in oncogenic transformation.
(ii) Agents that promote the proliferation of celis, which have already undergoes genetic alterations responsible oncogenic transformation. These agents are called tumour promoter e.g. some growth factors and hormones.

 
SiteLock