Cancer

  • Category: History
  • Words: 1209
  • Grade: 100
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

cancers certain lung cancers and may be a result of improvements

in disease detection and diagnosis cigarette smoking and an

increase of atmospheric pollutants are also thought to play a part.

        Increasing evidence implicates viruses in induction of cancer.

In the early 20th century Peyton Rous an American virologist

showed that certain fowl sarcomas could be transmitted by

injection of an agent invisible under the microscope and later

shown to be an RNA containing virus. Since then other oncogenic

or tumor causing viruses have been identified in experimental

animals. Viruses of the herpes group some of which cause cold

sores and chicken pox have been shown to cause cancer in

experimental animals. Recent evidence indicates that other

members of the herpes group such as the virus causing infectious

mononucleosis may cause human cancer. Human papillomavirus

has also been shown to cause or initiate cancers. Some types of

HPV cause genital warts known as condylomata acuminata which

appear to cause invasive cancer of the cervix, vulva, vagina, or

penis. There is evidence of synergistic effects of smoking and

some forms of HPV and cancer particularly cervical cancer in

woman. HPV 16 has been shown to be associated with some forms

of Kaposi's sarcoma. Surgical removal of the warts and lesions has

a 70% prevention of recurrence antiviral treatment with interferons

appear mildly successful when surgical removal is not successful.

        Some cancers may be triggered by changes in the body's

internal environment as hormone imbalances. A first reported in

1970 some daughters of mothers who had been given

diethylstilbestrol during pregnancy to prevent miscarriage

developed vaginal adenocarcinomas as young women. There are

genetic tendencies for certain types of cancer like breast or

stomach cancer and certain benign tumors like certain tumors of

the eye, cartilage, and skin, some of which may later become

malignant. Physical agents such as X-rays and radioactive elements

are also carcinogenic the high incidence of leukemia and other

cancers in Japanese survivors of the atomic bombing of Hiroshima

and Nagasaki is evidence of this carcinogenic effect. In light

skinned people who spend much time outdoors, sunlight may be

carcinogenic. Sometimes irritations and diseases may predispose

an individual to cancer, as in the occurrence of cancer of the

esophagus associated with frequently swallowing very hot liquids.

        Symptoms are often nonspecific like weakness, loss of

appetite, and weight loss. Sometimes side effects of tumor growth

are more severe than the actual effects of the malignancy like some

tumors secrete materials such as serotonin and histamine that can

cause drastic vascular changes. A tumor of an endocrine gland

such as an adrenal carcinoma may be responsible for producing

enormously increased numbers of hormone secreting cells. Cancers

that destroy tissue may also have serious effects like malignant

destruction of bone tissue may raise the blood level of calcium.

        Cancers can often be detected by visual observation palpation

X-ray study inspection by various optical probing instruments.

Cancers caught early before metastasis have the best cure rates.

Once they are found cancers are treated by surgery, chemotherapy,

and radiation. Surgery is most effective if the cancer is caught

while still localized. Some cancers that spread to the lymph system

have frequently prompted extensive surgical removal of tissue .

Many cancers formerly treated surgically are now being attacked

by other means such as radiation therapy. Use of radioactive

elements specific for particular target organs such as radioactive

iodine specific for the thyroid gland is effective in treating

malignancies of those organs. Lasers are used to treat certain

cancers and certain subatomic particles like pions, are being used

experimentally.

        Chemotherapeutic agents that are are used to selectively

destroy cancer cells. In general they interfere with nucleic acid and

protein synthesis rapidly proliferating cells like cancer cells are

most susceptible. Hormones such as and which may be

carcinogenic under some condition are also used in cancer

chemotherapy. Currently available chemotherapeutic agents are not

usually curative but merely ameliorate the severity of the disease

they are often toxic to normal rapidly proliferating cells such as

bone marrow cells. A chemotherapeutic technique known as

isolated perfusion can be used to minimize exposure to many toxic

drugs. In this method a pump and two tubes are attached to two

places in a network of blood vessels so that the drug only circulates

through the part of the system that is malignant.

        New approaches to cancer therapy still largely in the

experimental stage include immunological methods such as

vaccinating against cancer causing viruses or injecting sensitized

lymphocytes like antibody forming cells. Recent research is also

directed toward elucidating the cellular events that are manifested

as uncontrolled growth and cancer. The fact that there are many

ways to interfere with the controls on genes may help to explain

why cancer is apparently caused by a diversity of agents and why

agents that interfere with the expression of genetic information like

nitrogen mustard, radiation, and some hormones, are sometimes

carcinogenic and sometimes therapeutic.

        This report was very hard to do because I had to look up all

these big scientific words up in the dictionay. I hope you think I did

a good job and I hope to get an A+. The bibliography you wanted

is below.



Bibliography

D. M. Prescott, Cancer: The Misguided Cell (1973); Jay Roth, All

about Cancer (1985); R. Nery, Cancer (1986); Peter Farmer and

John Walker, ed., The Molecular Basis of Cancer (1985
ad 4
Copyright 2011 EssayTrader.net All Rights Reserved