Cancer

I chose to do my report on cancer because it is a subject I want to

learn about and because it can probably fit 5 pages. My

bibliography is on the ending of the report, my teacher helped me

with it because I didnt know how to do it. Cancer is the name for

tumors that are malignant. Malignant tumors do not respond to

body mechanisms that limit growing. Malignant tumors show a not

normal cell structure the same functional specialized cells. Also

cancer cells growing in laboratory tissue culture do not stop

growing when they touch each other on a glass or other solid

surface but grow in masses several layers deep they are said to lack

contact inhibition.

Loss of contact inhibition accounts for two other

characteristics of cancer cells invasiveness of surrounding tissues

and metastasis spreading via the lymph system or blood to other

tissues and organs. Cells are typically controlled by growth factors

competence factors that stimulate cells to enter the beginning phase

of cell replication and progression factors that insure completion of

the replication cycle. The unrestricted growth rates of cells are due

to the activation and lack of inhibition of oncogenes. They are

cancer causing genes.

Cancer tissue that grows without limits competes with normal

tissue for nutrients kills the normal cells by nutritional deprivation.

Cancerous tissue also causes secondary effects with the symptoms

of a malignant growth caused by the pressure of the growing tumor

against surrounding tissue or the metastasis of cancer cells and

their invasion of other organs. Cancers are graded as to degree of

malignancy on a scale of one through four the distinction between

even benign and malignant neoplasms is obscure. All organs and

tissues are susceptible to cancer.

A lot of human cancers may be caused or at least triggered by

various chemical agents. Alkylating agents are thought to have a

carcinogenic effect because they chemically alter the cell's nucleic

acids. Nitrites common additives in processed meat react with

amines in the stomach to form nitrosoamines which some

authorities believe may be carcinogenic to humans. Other

commonly occurring carcinogens are azo dyes, polycyclic

hydrocarbons, and urethane. Certain carcinogens present

occupational hazards. Asbestos particles once inhaled stay in the

lung and act as an irritant. In the asbestos and construction

industries workers have a high probability of developing a fatal

cancer of the chest lining or abdominal lining 25 to 30 years after

the initial inhalation of . Asbestos also has been linked to lung and

colon cancers in exposed individuals. Oral cancer common in India

is commonly attributed to the chewing of betel nuts. Although the

apparently increasing incidence of some types of highly malignant