10 Facts About the Small Intestine

The name “small” intestine is misleading considering the organ is around twenty feet long. The name comes from the fact that this portion is narrower than the large intestine. The length of the small intestine makes sense, considering it has one of the most important jobs in the entire GI tract, which consists of the mouth, esophagus, stomach, small and large intestine, and anus. Digestive health is dependent on all of these organs working in harmony to ensure proper nutrient absorption and waste removal.

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The small intestine is divided into three separate sections: the duodenum, jejunum, and ileum. Each part plays a specific role in digestion. The duodenum is the first in the series and moves digestive content from the stomach, liver, and pancreas into the jejunum. The jejunum begins the nutrient breakdown and absorption process. Finally, the ileum absorbs nutrients that may have been missed by the jejunum and then passes the remaining waste and digestive content to the large intestine.

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In addition to three sections, the small intestine is made up of four layers: the serosa, muscularis, submucosa, and mucosa. The serosa is the outside layer. As the name implies, the muscularis is a layer of muscle that expands and shortens the organ and constricts to move food through the GI tract. The submucosa is a layer of blood vessels, connective tissue, lymphatics, and nerves. The mucosa is the primary absorption layer that gathers the nutrients for conversion and distribution throughout the body.

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In addition to absorbing nutrients, the small intestine plays a vital role in the immune system by filtering out harmful gut bacteria. Not everything that passes through the small intestine requires absorption; the organ is also responsible for removing the unwanted digestive bacteria that the large intestine will dispose of as waste.

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The small intestine is responsible for moving food through the GI tract. The muscularis flexes to pass food through the small intestine in a series of contractions that allow for complete digestion and breakdown. This process can take hours to accomplish. In most cases, food requires three to five hours to pass from the duodenum to the ileum. This slow process ensures food is fully broken down and absorbed or filtered for removal.

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Poor movement through the small intestine can cause digestive disorders that range from short-term symptoms such as temporary pain, nausea, bloating, or constipation, to long-term conditions that may require medical treatment. Foods the body dislikes cause most minor digestive complaints while more serious disorders are often due to improper functioning. A complete and well-rounded diet can be one of the best ways to ensure digestive health.

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In addition to the poor movement of food through the digestive tract, too much bacteria can prohibit complete digestion by preventing the absorption of nutrients. Symptoms are similar to those of poor movement and include pain and bloating, as well as diarrhea. Improper muscle contraction and poor food movement in the digestion process are the main causes of too much bacteria in the small intestine.

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The small intestine loves fiber because the carbohydrate aids nutrient absorption and helps control the movement of food through the digestive process, enabling complete absorption of nutrients. Fiber also allows for better movement from one digestive organ to the next. There are various types of fiber, however, and the organ does not view all fibers as equal. Dietary fibers that feed the “good” bacteria provide the most digestive health benefits.

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Stress can have a negative impact on health and well-being, and it can also limit the effectiveness of the small intestine. When a person is stressed, the body is less capable of completing the digestive process efficiently, and this means poor nutrient absorption and incomplete digestion. Minimizing and managing stress ensures the body has the proper time and energy to process food as fuel.

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As noted, the small intestine has multiple layers, including muscles. Like any other muscle group, the small intestine can break down with age, and requires exercise for optimal performance -- strong and healthy muscles greatly improve efficiency. Many digestive issues appear in older adults as muscles breakdown over time. In addition to aging, a sedentary lifestyle can have a negative impact on digestion. Regular exercise will ensure food moves through at the correct pace and with the desired result.

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