Digestion is defined as the process of breaking down foods into smaller components that your intestines can absorb. Digestion is an important aspect of nutrition, because it is through this process that your body gains access to the nutrients it needs to function properly. Every area of the digestive tract, which includes your mouth, stomach, small intestine and large intestine, plays a different but equally important role in the digestive process.
Mouth
Digestion begins when you see or smell food. The salivary glands in your mouth release saliva, which contains water, mucus and a digestive enzyme called salivary amylase. The water in your saliva adds moisture to food, and the salivary amylase breaks it down into smaller chemical particles. The mucus in your saliva helps the food stick together and protects the mouth and esophagus from any harm. You also use your teeth to grind food down into smaller pieces. Once food has been chewed thoroughly, it travels to the back of the throat so that you can swallow it.
Stomach
Swallowed food travels through a tube, called the esophagus, which connects your mouth to your stomach. The food travels through the esophagus until it reaches a band of muscle called the lower esophageal sphincter, which opens to allow the food to pass into the stomach and then closes to prevent food from traveling backward. Once food enters the stomach, the stomach begins to churn and contract to mix the food with digestive enzymes and hydrochloric acid. This helps break the food down so that it can continue through the digestive tract.
Small Intestine
Most digestion and absorption takes place in your small intestine. By the time the food you eat travels to the small intestine, it is thoroughly broken down, but the digestive juices in the small intestine break it down into absorbable nutrients. Small projections called villi and even smaller projections called microvilli absorb the nutrients and deposit them into your bloodstream.
Large Intestine
Once the food reaches the large intestine, most digestion has already taken place. The main functions of the large intestine are to absorb water and form fecal matter to remove wastes from your body. Once fecal matter forms, it travels to an area of the large intestine called the rectum, where it sits until it is eliminated through the anus.
Considerations
Although not an official part of the digestive tract, the liver, gallbladder and pancreas also play a role in digestion. The liver produces a digestive fluid, called bile, which is stored in the gallbladder. The gallbladder releases bile into the digestive tract when needed to digest fats. The pancreas releases various enzymes that are needed to chemically break down food in your digestive tract.
References
- "Nutrition and You"; Joan Salge Blake; 2008
- National Digestive Diseases Information Clearinghouse; Your Digestive System and How It Works; April 2008
