INTESTINES.

The intestines are a long, continuous tube running from the stomach to the anus. Most absorption of nutrients and water happen in the intestines. The intestines include the small intestine, large intestine, and rectum.

The small intestine (small bowel) is about 20 feet long and about an inch in diameter. Its job is to absorb most of the nutrients from what we eat and drink. Velvety tissue lines the small intestine, which is divided into the duodenum, jejunum, and ileum.

The large intestine (colon or large bowel) is about 5 feet long and about 3 inches in diameter. The colon absorbs water from wastes, creating stool. As stool enters the rectum, nerves there create the urge to defecate.

Intestine Conditions

• Stomach flu (enteritis): Inflammation of the small intestine. Infections (from viruses, bacteria, or parasites) are the common cause.
• Celiac disease: An "allergy" to gluten (a protein in most breads) causes the small intestine not to absorb nutrients properly. Abdominal pain and weight loss are usual symptoms.
• Carcinoid tumor: A benign or malignant growth in the small intestine. Diarrhea and skin flushing are the most common symptoms.
• Intestinal obstruction: A section of either the small or large bowel can become blocked or twisted or just stop working. Belly distension, pain, constipation, and vomiting are symptoms.
• Colitis: Inflammation of the colon. Inflammatory bowel disease or infections are the most common causes.
• Colon bleeding (hemorrhage): Multiple potential colon problems can cause bleeding. Rapid bleeding is visible in the stool, but very slow bleeding might not be.
• Inflammatory bowel disease: A name for either Crohn's disease or ulcerative colitis. Both conditions can cause colon inflammation (colitis).
• Diarrhea: Stools that are frequent, loose, or watery are commonly called diarrhea. Most diarrhea is due to self-limited, mild infections of the colon or small intestine.
• Colon cancer:  Most colon cancer is preventable through regular screening.
• Rectal cancer: Colon and rectal cancer are similar in prognosis and treatment. Doctors often consider them together as colorectal cancer.
• Constipation: When bowel movements are infrequent or difficult.