Crohn's Disease Anatomy

Reviewed on 12/2/2021

What Is Crohn's Disease, Which Parts of the Digestive System Does It Affect?

Picture of Crohn's Disease
Picture of Crohn's Disease

Crohn's disease is a chronic inflammation of the digestive tract. Crohn's disease is one of the many types of inflammatory bowel disease or IBD. Ulcerative colitis or UC also is an IBD.

Any part of the digestive tract from the mouth to the anus can be involved in Crohn's disease, although it most commonly affects the end of the small intestine called the terminal ileum and the beginning of the large intestine called the cecum. The inflammation may extend deep into the tissues of the organ that is affected.

Organs of the digestive system include the:

What Are the Parts and Functions of the Digestive System?

  • The digestive system is made up of the digestive tract, which is a long series of organs, including the esophagus, the stomach, the small intestine, and the large intestine, that runs from the mouth to the anus.
  • The digestive tract in an adult is about 30 feet long.
  • Digestion begins in the mouth where saliva begins to break down food. Food is swallowed from the mouth into the esophagus, which then moves the chewed food to the stomach. The stomach has strong muscular walls that mix and churn the food with acid and enzymes (known as gastric juice), breaking the food into smaller pieces. The processed semiliquid food, called chyme, is slowly released from the stomach into the small intestine.
  • Most digestion and absorption occur in the small intestine. The small intestine has 3 parts: 1) the duodenum, 2) the jejunum, and 3) the ileum.
  • Enzymes and other substances made by intestinal cells, the pancreas, and the liver are secreted into the small intestine and break down starches, sugars, fats, and proteins. Absorption of nutrients occurs through the millions of tiny fingerlike projections called villi and the even tinier projections on the villi called microvilli.
  • Any undigested material moves to the large intestine. The large intestine or colon has four sections called the 1) cecum/ascending colon, 2) transverse colon, 3) descending colon/sigmoid, and 4) rectum.
  • The main job of the large intestine is to remove water and salts (electrolytes) from the undigested material and to form solid waste (feces) that can be excreted. The remaining contents of the large intestine move to the rectum, where feces are stored until they leave the body through the anus as a bowel movement.

What Are the Signs and Symptoms of Crohn's Disease?

The inflammation from Crohn's disease may cause signs and symptoms of pain in the abdomen that may make the intestines empty frequently, resulting in diarrhea.

Other symptoms of Crohn's disease include

Signs and symptoms of complications of Crohn's disease are urinary tract infection (UTI) or vaginal infection.

What Are the Complications of Crohn's Disease?

The following may occur in the digestive tract due to the complications of Crohn's disease:

  • Blockage in the intestine due to thickening of the intestinal walls
  • Ulcers or fissures may tunnel through the affected area into surrounding areas (for example, bladder, vagina, skin).
  • Fistulas (communication between the intestine and other adjacent organs) may develop.
  • Thickening of the wall due to acute inflammation may narrow the lumen of the small intestine.
  • Scar tissue resulting from the healing process also may lead to a narrowed bowel.
  • Strictures

Why Is Diet So Important for People with Crohn's Disease?

Nutritional complications are common in Crohn's disease.

  • Protein, calorie, and vitamin deficiencies may be due to inadequate dietary intake, loss of protein in the intestine, or poor absorption.
  • Depending on what part of the intestine is affected, the symptoms and complications may differ.

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Can Crohn's Disease Be Cured?

The primary focus of treatment of Crohn's disease is to prevent flares, and to lessen and relieve symptoms. Doctors prescribe anti-inflammatory drugs like aspirin, mesalamine, (Asacol, Pentasa), corticosteroids, and antibiotics, immunosuppressant drugs, and biologic therapy.

Reviewed on 12/2/2021
Ghazi, LJ, MD, et al. "Crohn Disease." Medscape. Udpated: Jul 26, 2019.