1. It All Starts in the Mouth
The mouth is part of the digestive system and is responsible for more than just chewing food into small pieces for easier swallowing. Saliva contains the amylase enzyme, which breaks down starches into simple sugars. Chew on a piece of bread for a few extra seconds, and you will taste the sweet flavor of starches converting to sugars. Saliva also contains lysozyme, which kills bacteria in food. People with insufficient saliva production should talk to their doctors about artificial saliva replacements to improve digestion and quality of life.
2. The Digestive System has a Mind of its Own
The digestive system has its own central command station: the enteric nervous system. The nerves of this system lie throughout the digestive system and control its muscle and secretory activities in response to signals from the central nervous system. The nerves that govern the digestive system are complex, leaving the digestive system vulnerable to malfunction and disease. For example, patients can sometimes experience intestinal paralysis after surgery. The resulting inability to turn off inhibiting nerve signals shuts down normal intestinal movements, causing painful gas and bowel distension.
3. Keep it Movin'
If you've ever taken a gulp of water while lying down, you know there's more than gravity at work as food and beverages work their way through your digestive system. One group of muscles squeezes behind the ingested food and relaxes in front of it, keeping the food moving forward. Another group of muscles arranged lengthwise in the digestive system contracts to make the digestive system shorter. Laxatives stimulate the muscles responsible for peristalsis, which can lead to decreased muscle tone over time. Eating more fiber will gently stimulate peristalsis and increase stool bulk.
4. Enzymes Hasten the Process
Enzymes are the facilitators in the digestive system, as they create an environment enabling important chemical reactions to occur. The small intestine and pancreas produce most digestive enzymes, but the stomach and mouth produce some, too. If disease prevents the stomach or pancreas from producing enzymes essential to digestion, the body can fail to absorb important nutrients. Doctors offer replacement enzymes to prevent this problem.
5. The Small Intestine Workhorse
Most nutrient absorption takes place in the small intestine. With myriad folds and brush-like projections, the small intestine has a surface area 600 times greater than that of a simple tube. These folds trap food and absorb about 95 percent of the calories that pass through it. Some patients with gluten intolerance experience a flattening of these absorptive projections, exacerbated by the gluten found in barley, oats, wheat and rye. Patients with celiac disease must avoid these gluten-rich foods.
