Healthy Digestive System
Both the rectum along with the colon belong to the digestive system. This is also known as the GI or gastrointestinal system – as shown in the illustration. In the early stages of the digestive tract – the small intestine and stomach – food is processed and used for energy. The latter part – the rectum and colon – takes fluid and forms it into solid waste – otherwise known as stool or fecal matter – which then leaves the body. If you wish to understand more about colorectal cancer, learning about how a healthy digestive system works is a good idea.
Once food has been processed by the mouth, it moves down the esophagus to your stomach. At that point, it is broken down partially and sent further down until it reaches the small intestine – the small bowel. It’s known as such as it is more narrow than the large intestine (which is the rectum and colon). Interestingly, even though it’s narrower, it’s the longer of the two, reaching to 20 feet or so. This is where most of the food gets broken down, and the majority of all the nutrients are absorbed from.
Once in the lower abdomen, the small intestine meets up with the large one. The large intestine stretches out about five feet and is mainly a tube that is muscular – the colon. Absorbing salt and water from food, the colon acts as a waste storage place.
Four Section Colon
The ascending colon is the first part of the colon. It begins with the cecum (a tiny pouch.) This is where the colon attaches on to the small bowel, extending upward toward the right of the abdomen. Also, the colon affixes to the appendix here.
Secondly, is the transverse colon. So named because it crosses the body, starting on the right and moving left.
Third is the descending colon, which continues down the left side.
Last and fourth is the sigmoid colon, named from its sigmoid or “S” shape.
The leftover waste after traveling throughout the colon is known as stool or feces. This is pushed along to the last 6 inches – the rectum – where it waits to be passed from the body out of the anus.
Both the rectum and colon wall are layered (see accompanying illustration located at the staging section). The most inner layer is where colorectal cancer begins. It can work its way through all or just some of the layers. It a good idea to understand a bit about these different layers as the stage of the cancer (extent of the spread) hinges to a large part on how deep it moves into the layers.
Unusual rectum or colon growths
The majority of these types of cancers grow slowly over a period of years. Previous to it becoming cancer, a tumor or abnormal tissue growth starts on the rectum or colon’s inner lining as a polyp that is non-cancerous. Tumors (which may either be benign or cancerous) are abnormal tissues. A polyp is a tumor that is non-cancerous. Sometimes polyps change and become cancerous, however, not all of them. The type of polyp determines the chance it has of turning cancerous. There are a couple of polyp types: