Specialized Eukaryotic Cells and Tissues
Cancer is a disease in which cells begin to divide when they shouldn’t, producing masses of cells called tumors. Cancerous tumors are called “malignant” ones because of their ability to grow aggressively, invade surrounding healthy tissue, and “metastasize”, or spread to different locations in the body as tumor cells break off, travel through the blood or lymph, and establish new tumors.
Cancer is generally caused by environmental agents known as “carcinogens”, which include chemicals (such as those found in cigarette smoke) and radiation (like the UV rays of sunlight) that mutate cells, causing them to become cancerous.
Tumors that originate from epithelial cells are generally known as carcinomas, and it is estimated that about 90% of all human cancers are carcinomas. Tumors that originate from muscle tissue are called “sarcomas”, and tumors can also originate from nervous and connective tissues. Epithelial tissue exists in various locations in the body, including the skin, the mucous membranes lining the lungs and gastrointestinal tract, and the linings surrounding major organs.
A lab worker in Alaska develops a carcinoma of the skin. This particular worker is very dedicated, and almost never leaves the lab. The tumor is most likely the result of:
|A||Excessive cigarette smoking by coworkers.|
|B||Excessive ingestion of toxic chemicals.|
|C||Exposure to radiation from phosphorus-32, a radioactive isotope the worker routinely uses.|
|D||Exposure to ultraviolet rays of sunlight.|
The cause of a carcinoma of the skin would most likely be radiation exposure from the environment, or contact with the skin by carcinogenic chemicals. Since the worker lives in Alaska and rarely goes outside, it is unlikely that excessive exposure to sunlight is the culprit, and radiation from the isotope is a more likely causative agent. Cigarette smoke or ingestion of chemicals would likely affect mucous membranes or internal body parts.