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8

NCCN Guidelines for Patients

®

:

Colon Cancer, Version 1.2017

You’ve learned that you have colon

cancer. It’s common to feel shocked and

confused. Part 1 reviews some basics that

may help you learn about colon cancer.

The colon

Before learning about colon cancer, it is helpful

to know about the colon. The colon is part of the

digestive system. This system breaks down food for

the body to use.

Digestive tract

After being swallowed, food moves through four

organs known as the digestive tract.

See Figure 1

.

First, food passes through the esophagus and into

the stomach.

In the stomach, food is turned into a liquid. From

the stomach, food enters the small intestine. In the

small intestine, food is broken down into very small

parts. This allows nutrients to be absorbed into the

bloodstream.

From the small intestine, food moves into the large

intestine. The large intestine changes unused food

from a liquid into a solid by absorbing water. This

solid, unused food is called feces or stool. The large

intestine also expels stool from the body.

The colon is part of the large intestine. It is almost

5 feet long. Its four parts are the ascending,

transverse, descending, and sigmoid colon.

Colon wall

The wall of the colon has four main layers.

See

Figure 2

. The inner layer that has contact with stool

is called the mucosa. The mucosa consists of three

sublayers. They are the epithelium, lamina propria,

and muscularis mucosae.

The epithelium absorbs water from stool and makes

mucus. Mucus is a sticky, thick liquid that protects

the colon. It also helps move stool through the colon.

The lamina propria is a thin layer of connective

tissue. The muscularis mucosae is a thin strip of

muscle.

The second layer of the colon wall is called the

submucosa. It consists of connective tissue, blood

and lymph vessels, and nerve cells. Lymph is a

clear fluid that gives cells water and food. It also has

white blood cells that fight germs. Blood and lymph

drain from colon tissue into vessels that are in the

submucosa and then travel to other sites.

The third layer of the colon wall is called the

muscularis propria. It is mostly made of muscle

fibers. These muscles help move stool through the

colon.

The fourth layer is the outer most part of the colon

wall. It consists either of adventitia or serosa.

Adventitia is connective tissue that binds the colon to

other structures. The serosa, also called the visceral

peritoneum, is a membrane.

The serosa contains has a thin layer of connective

tissue. This tissue is called the subserosa. It is

covered by a single row of cells that make fluid. This

fluid allows the colon to move smoothly against other

organs.

1

Colon cancer basics

The colon