Your digestive, or gastrointestinal, tract consists of your mouth, esophagus, stomach, small intestine, large intestine and accessory organs, such as the pancreas and gallbladder. After you eat, the food you consume travels through each portion of the digestive tract, whose main roles are to break the food down and absorb nutrients from it.
Mouth
The process of digestion begins in your mouth. When you see, smell or taste food, your salivary glands release saliva, a fluid that contains various enzymes. When you chew, your teeth break food down into small pieces and your tongue mixes those pieces with saliva. Saliva adds moisture to the food and helps to dissolve some of the particles. When the food has been chewed thoroughly, it moves to the back of the throat so you can swallow it. The food then travels through your esophagus and into your stomach.
Stomach
Once the food is swallowed, it is considered a bolus. The bolus moves into the stomach, which produces various digestive juices and hydrochloric acid. The stomach moves and churns to mix these juices and acids with the bolus. The bolus is broken down and becomes chyme, which is mostly liquid. Contractions in your stomach, called peristaltic contractions, move the chyme to a muscle called the pyloric sphincter that separates the stomach from the small intestine. The pyloric sphincter allows the chyme into the small intestine and prevents it from flowing back into your stomach.
Small Intestine
Once the chyme reaches your small intestine, it is broken down into nutrients. The small intestine is lined with finger-like projections called villi that mix the chyme with digestive secretions from the small intestine to allow nutrient absorption. Most of the digestion and absorption of nutrients takes place in your small intestine, according to "Nutrition and You" by Joan Salge Blake. Once nutrients are adequately absorbed, the chyme moves into the large intestine.
Large Intestine
When the chyme reaches the large intestine, it is completely digested and most nutrients have been absorbed. The large intestine absorbs water and various electrolytes from what is left in the chyme. Once water and electrolytes are adequately absorbed, the chyme moves to the colon, where it is compacted into fecal matter. The fecal matter passes through the colon and to the rectum, the lower portion of the large intestine. The stool is stored in the rectum until it is eliminated from your body through your anus.
Accessory Organs
The pancreas, liver and gallbladder produce various hormones and enzymes that help aid in the process of digestion. The liver also produces a substance called bile that helps break down fat in the digestive tract. The release of these hormones is stimulated by the presence of different types of foods in your digestive tract.
References
- "Nutrition and You"; Joan Salge Blake; 2008
- National Digestive Diseases Information Clearinghouse: Your Digestive System and How it Works
