Digestion is one of the most important processes our bodies perform. Every time we eat, food must be broken down and converted into energy and fuel. The body uses this energy and fuel for growth and cell repair. Digestion begins at the mouth and ends at the anus. In between these places, food moves along as the process converts it into smaller, more usable pieces through an array of enzymes and hormones. It's a long journey for the food we eat as it travels through the digestive system, and it all starts when we take a bite.
The digestion process starts in the mouth. As soon as you take a bite of food, you are kickstarting the body's digestive response, which takes around six to eight hours to complete. It all starts with chewing. We use our teeth to break down our food into smaller, easy-to-swallow pieces. The more you chew, the easier it is for the body to digest the food you eat. This is most likely why your mother always used to remind you to chew your food instead of scarfing it down!
The second step in digestion also takes place in the mouth. While you are chewing, saliva mixes with the food. The saliva starts the process of breaking this food down into a form your body can convert into energy. Without saliva, the body cannot absorb the nutritional benefits -- this is another reason why the longer you chew your food, the better: the more saliva with which the food is saturated, the most you'll get out of it during the rest of its journey.
After the food has been chewed and your saliva has begun to break it down, it enters the throat or pharynx -- the third step in the digestion process. Food doesn't normally stay here long (unless you choke, which is not helpful for digestion!); this is just a quick stop on the journey. Food travels from the mouth, through the throat when we swallow, and then on to the esophagus.
The esophagus is a tube of muscle that connects the throat to the stomach. It contracts in a process called peristalsis, which moves the food through the tube. When the chewed food gets to the end of the tube, it enters a "zone of high pressure" -- the lower esophageal sphincter. This acts as a valve to keep the food from passing back up through the esophagus. Problems with this valve lead to conditions like heartburn, in which acid or partially digested food rise back up the throat and cause burning or pain.
When most people think of digestion, they think of the stomach. This is where the real magic happens. The stomach not only holds the food you have eaten, it also grinds it up into an entirely new form. Using powerful acids and enzymes, it continues the process the saliva started, breaking down the food into something our bodies can more easily use. When the food finishes its time in the stomach, it is the form of a liquid or a paste and is ready for the next phase.
The small intestine is a long tube (more than 20 feet long, in fact!) made up of three segments: the duodenum, the jejunum, and the ileum. It uses enzymes produced by the pancreas to break down food even more, with help from bile produced by the liver. The bile is especially important, as it gets rid of waste products from the blood. More muscle contractions move the food along the tube. In the duodenum, the food breaks down; then, the nutrients absorb into the bloodstream with the help of the jejunum and ileum.
This step in the process is removed from the others. Food never actually enters the gallbladder, but the pear-shaped organ does assist in the digestion process. It sits under and stores the bile produced by the liver. As we eat, the gallbladder contracts and sends bile to the small intestine to help digest the food. Once the food has been turned completely into liquid, it continues its journey through the small intestine and ends up in the colon or large intestine.
The colon is another tube of muscle that is five to six feet long. It connects the cecum (the opening to the large intestine) to the rectum. Here, waste left over from the digestion process is transformed into something the body can eliminate. Contractions move the liquid from the previous steps along the colon, changing it into a more solid form: stool.
Stool is the waste resulting from the digestion process. The colon produces this waste and stores it in the sigmoid colon. It remains here until a "mass movement" or series of contractions causes it to empty into the rectum. This normally happens once or twice a day, and is what prompts bowel movements. The stool that exits the body is mostly made up of leftover food debris and the bacteria used by the body to keep us safe from more harmful bacteria.
When the food arrives at the rectum, it has almost reached the end of its digestive journey. The rectum is an eight-inch-long chamber that connects the large intestine to the anus. Its purpose is to accept the delivery of stool from the colon and alert you that there is waste to release. It sends a message to the brain, and the brain decides whether it is a good time or place to release its contents -- in other words, whether or not we need to go to the bathroom. If the answer is yes, the muscles relax and the rectum expels its contents, which exit our bodies through the anus, ending the process of digestion.
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