Digestion involves a succession of mechanical and chemical actions that convert food into energy and waste. As you ingest food, it moves down a long, internal tube, originating in the neck, and running the entire length of the chest and abdomen. This tube connects a series of organs designed to break down food and absorb nutrients. The basic digestive process typically takes between 24 to 72 hours from start to finish, according to Michael Picco, M.D., of MayoClinic.com.
Mouth
You begin digesting food the moment it enters your mouth. Chewing grinds and tears food into smaller pieces. Saliva, secreted by your salivary glands, softens chewed food, allowing it to pass easily from the mouth into the throat. Saliva also contains the enzyme amylase, which initiates the breakdown of carbohydrates. Muscles and nerves in the mouth and throat work together to induce swallowing. Swallowing propels chewed food from the mouth into the throat. Food then passes into and through your esophagus, on its way to the stomach.
Stomach
Food reaches your stomach after moving through a muscular junction, known as the esophageal sphincter. It opens and closes, allowing the passage of food and preventing caustic gastric juices from entering the esophagus. The stomach plays an important role in the digestive process. It serves as a storage chamber for liquid, food and gastric juices. Your stomach produces gastric acid, which breaks down carbohydrates, protein and fat. Muscle contractions in the stomach combine gastric acid and food in preparation for transport to the small intestine.
Small Intestine
The small intestine measures up to 20 feet long. Dr. Bill Salt, Sharecare expert, emphasizes the importance of this digestive organ, saying, "Most digestion and absorption takes place in the small intestine." The upper portion of the small intestine, called the duodenum, secretes mucus to protect its delicate lining from stomach acid. Your food continues to break down and emulsify as it merges with secretions from the intestine, pancreas and liver. Nutrients absorb into the bloodstream via villi, tiny hairlike projections covering the intestinal walls. Unused food matter then moves into the large intestine.
Large Intestine
Your large intestine, or colon, acts as a holding area for undigested food before it leaves the body. According to a report from BBC Health, the large intestine contains more than 400 types of beneficial bacteria that assist in the decomposition of fibrous food and manufacture of nutrients. Food enters the large intestine as a mix of solids and liquid. The colon absorbs most of the liquid prior to elimination. The byproduct, feces, exits the body via the rectum.
References
- National Digestive Diseases Information Clearinghouse; Your Digestive System and How It Works; April 2008
- MayoClinic.com; How Long Does It Take to Digest Food; Michael Picco, M.D.; August 2010
- Kids Health: How Does Digestion Work?
- Cleveland Clinic: The Structure and Function of the Digestive System
- Sharecare; What Is the Function of the Small Intestine?; William B. Salt, II, M.D.
- BBC Health; The Digestive System; Fiona Hunter; April 2011
