Colon (Large Intestine)

The colon, commonly referred to as the large intestine, is an essential part of the human digestive system, playing a crucial role in how our bodies process waste and absorb water and nutrients.

What is the Colon?

The colon is the final part of the gastrointestinal (GI) tract in the human digestive system, following the small intestine. It functions primarily to extract water and salt from solid wastes before they are eliminated from the body. The colon is about 5 feet long and comprises several sections: the ascending colon, the transverse colon, the descending colon, the sigmoid colon, and the rectum.

Structure of the Colon

  • Ascending Colon: Begins at the cecum, just after the small intestine, and travels up the right side of the abdomen.
  • Transverse Colon: The longest section, which crosses the abdominal cavity from right to left.
  • Descending Colon: Travels down the left side of the abdomen.
  • Sigmoid Colon: An S-shaped segment that connects to the rectum.

The walls of the colon are made up of several layers of muscle and mucous membranes. These layers help in the movement of waste and the absorption of water and minerals.

Function of the Colon

The primary functions of the colon are:

  • Water Absorption: As waste material travels through the colon, water is absorbed back into the body, significantly reducing the volume of waste.
  • Electrolyte Absorption: Sodium and chloride ions are also absorbed from the waste.
  • Formation of Stool: By the time the waste reaches the sigmoid colon, it has formed solid stool, ready to be expelled during defecation.

The colon also houses a vast amount of bacteria that play a role in gastrointestinal health, such as aiding in digestion, producing vitamins (like vitamin K and some B vitamins), and defending against harmful bacteria.

Common Disorders of the Colon

1. Colorectal Cancer

Colorectal cancer is one of the most common types of cancer diagnosed in the United States. It typically develops from polyps, which are growths that form inside the colon. Early detection through screening such as colonoscopies can lead to effective treatment.

2. Crohn’s Disease

This is a type of inflammatory bowel disease (IBD) that can affect any part of the GI tract but is often found in the ileum and the beginning of the colon. Crohn’s disease is characterized by inflammation, which can lead to symptoms like pain, severe diarrhea, fatigue, and weight loss.

3. Ulcerative Colitis

Another form of IBD, ulcerative colitis, specifically affects the lining of the colon and rectum. It causes long-lasting inflammation and sores (ulcers) on the innermost lining of the large intestine.

4. Diverticulitis

Diverticulitis occurs when small, bulging pouches (diverticula) that develop along the digestive tract become inflamed or infected. It can cause severe abdominal pain, fever, and a marked change in bowel habits.

5. Irritable Bowel Syndrome (IBS)

While not directly involving the colon alone, IBS affects the large intestine and can cause cramping, abdominal pain, bloating, gas, diarrhea, and constipation. IBS is a chronic condition that needs to be managed long term.

Care and Prevention

Maintaining colon health is crucial. Here are some tips:

  • Diet: Eating a high-fiber diet from fruits, vegetables, and whole grains can help keep your colon healthy.
  • Hydration: Drinking plenty of fluids promotes good digestion and supports the functions of the colon.
  • Regular Screening: Especially if you are over the age of 45 or have a family history of colon cancer.
  • Exercise: Regular physical activity can enhance your digestive health and help you maintain a healthy weight.


The colon plays an indispensable role in the digestive system. It helps in the absorption of water and electrolytes, the formation and elimination of feces, and houses beneficial bacteria that contribute to health. Understanding the functions and potential issues related to the colon can help you maintain better digestive health.