(From cancer.org)
What is colorectal cancer?
Colorectal cancer?is cancer that starts in the colon or the rectum. These cancers can also be referred to separately as colon cancer or rectal cancer, depending on where they start. Colon cancer and rectal cancer have many features in common.
The colon and rectum are parts of the digestive system, which is also called the gastrointestinal (GI) system (see illustration). The first part of the digestive system (the stomach and small intestine) processes food for energy while the last part (the colon and rectum) absorbs fluid to form solid waste (fecal matter or stool) that then passes from the body. To understand colorectal cancer, it helps to know something about the normal structure of the digestive system and how it works.
After food is chewed and swallowed, it travels through the esophagus to the stomach. There it is partly broken down and then sent to the small intestine, also known as the small bowel. It is called the small intestine because it is narrower than the large intestine (colon and rectum). Actually the small intestine is the longest segment of the digestive system ? about 20 feet. The small intestine continues breaking down the food and absorbs most of the nutrients.
The small intestine joins the large intestine (or large bowel) in the right lower abdomen. Most of the large intestine is made up of the colon, a muscular tube about 5 feet long. The colon absorbs water and salt from the food matter and serves as a storage place for waste matter.
In most people, colorectal cancers develop slowly over several years. Before a cancer develops, a growth of tissue or tumor usually begins as a non-cancerous?polyp?on the inner lining of the colon or rectum. A tumor is abnormal tissue and can be benign (not cancer) or malignant (cancer). A polyp is a benign, non-cancerous tumor. Some polyps can change into cancer but not all do. The chance of changing into a cancer depends upon the kind of polyp:
- Adenomatous polyps (adenomas)?are polyps that can change into cancer. Because of this, adenomas are called a pre-cancerous condition.
- Hyperplastic polyps and inflammatory polyps, in general, are not pre-cancerous. But some doctors think that some hyperplastic polyps can become pre-cancerous or might be a sign of having a greater risk of developing adenomas and cancer, particularly when these polyps grow in the ascending colon.
Another kind of pre-cancerous condition is called?dysplasia. Dysplasia is an area in the lining of the colon or rectum where the sells look abnormal (but not like true cancer cells) when viewed under a microscope. These cells can change into cancer over time. Dysplasia is usually seen in people who have had diseases such as ulcerative colitis or Crohn?s disease for many years. Both ulcerative colitis and Crohn?s disease cause chronic inflammation of the colon.
jack and jill uss carl vinson holly marie combs unc basketball college basketball gunsmoke papelbon
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.