What Is Inflammatory Bowel Disease

Anatomy and Function of the GI Tract

In order to understand inflammatory bowel disease (IBD), it is first helpful to understand the anatomy and function of the healthy gastrointestinal (GI) tract.

Here is a medical illustration of the GI tract: 

As you can see, when you eat, food travels through the GI tract in the following order:

1. Mouth
    
2. Esophagus (the tube that connects the mouth to the stomach)
    
3. Stomach (where food is mixed with stomach acid and enzymes to break down the material into smaller pieces called chyme)
    
4. Small Bowel (also known as the Small Intestine) which is made up of three sections known as the:

• Duodenum (about 8 cm in length)
• Jejunum (can be around 3 metres long)
• Ileum (can also be approximately 3 metres in length)

The functions of the small bowel are to digest your food and absorb the nutrients that are necessary for life. Many people believe that this is the purpose of the stomach but that is not true. In actual fact, the small bowel (particularly the jejunum and ileum) is the organ responsible for absorbing nutrients from your food. Without the small bowel, we would not be able to convert food into useable nutrition.

5. Ileocecal Valve (which regulates the amount of material passed from the small bowel to the large bowel and prevents “dumping” all at once

6. Large Bowel (also called the Large Intestine or the Colon). The colon is much wider in diameter than the small bowel and is approximately 1.5 metres long. Once again, there are sections of the colon which are identified by different names to enable discussion about clinical issues :

• Cecum and appendix
• Ascending colon
• Hepatic flexure (a bend in the gut at close to the location of the liver)
• Transverse colon
• Splenic flexure (another bend located near the spleen)
• Descending colon
• Sigmoid colon
• Rectum
• Anus

The main functions of the colon are to extract water and salt from stool, and store it until it can be expelled via the anus. When stool first enters the colon from the small bowel, it is very watery. As it traverses the large bowel, water is reabsorbed and the stool gradually becomes firmer.

The Scoop on Poop

Let’s talk a bit about stool, also known as feces. It may seem glib and a bit crass to kid around about toilet humour and “the scoop on poop” however, the fact of the matter is that bowel function is a normal, absolutely necessary function of the human body.

When it is not normal - as with IBD - all kinds of trouble can result. We, like many who deal with IBD, address the issues of bowel function and feces in a direct manner, and occasionally with humour, we do so with the best of intent and the desire to help you face this disease openly and frankly. Our aim is to take IBD out of the shadows where it will remain unless more people talk about it directly.

Stool or feces, is the by-product of digestion through the GI tract. In a healthy individual, it is usually composed of water, dead and living bacteria, fiber (undigested food), intestinal mucous and sloughed-off lining of the gut. It is not normal to have blood in feces, nor large amounts of mucous. Feces from an individual without any gut disease is soft enough to pass comfortably from the rectum and anus, and (depending on the person) is typically expelled one or two times a day.

Bowel movements are an entirely different matter for someone with IBD. If you have IBD, there are some very real challenges related to feelings of urgency, diarrhea and bloody stool. 

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