Colorectal cancer

Colorectal carcinoma, also known as colon cancer, is when malignant or cancerous cells arise in the large intestines, which includes the colon and rectum.

It is the most common type of cancer of the gastrointestinal tract, and a major cause of death and disease around the world.

The large intestine is found in the abdominal cavity, which can be thought of as having two spaces - the intraperitoneal space and the retroperitoneal space.

The intraperitoneal space contains the first part of the duodenum, all of the small intestines, the transverse colon, sigmoid colon, and the rectum; the retroperitoneal space contains the distal duodenum, ascending colon, descending colon, and anal canal.

So the large intestines essentially weave back and forth between the intraperitoneal and retroperitoneal spaces.

Now, the walls of the gastrointestinal tract are composed of four layers. The outermost layer is the called serosa for the intraperitoneal parts, and the adventitia for the retroperitoneal parts.

Next is the muscular layer, which contracts to move food through the bowel.

After that is the submucosa, which consists of a dense layer of tissue that contains blood vessels, lymphatics, and nerves.

And finally, there’s the inner lining of the intestine called the mucosa; which surrounds the lumen of the gastrointestinal tract, and comes into direct contact with digested food.

The mucosa has invaginations called intestinal glands or colonic crypts, and it’s lined with large cells that are specialized in absorption.