A Look Inside Your Digestive System

Have you ever noticed how your mouth starts watering at the sight of your favorite food? That's because digestion begins in your mouth. Your teeth grind the food you eat and mix it with saliva to form a kind of ball, known as a bolus. During the mixing, an enzyme called salivary amylase starts breaking down carbohydrates. Once the food is soft and relatively flexible, the tongue pushes it to the back of your mouth and swallows it down the esophagus.

Your esophagus is a flattened, muscular tube that connects your mouth to your stomach. As food is swallowed, your esophagus expands. It takes food between one to eight seconds to pass through your esophagus, depending on how soft the food you ate is.

Common problems of the esophagus include heartburn, acid reflux, and gastroesophageal reflux disease (GERD), all of which are caused by acid flowing up from the stomach and irritating the lower part of the esophagus.

Your stomach is a J-shaped muscular pouch, which receives food from your esophagus and sends it to your small intestine. Inside your stomach, food is churned around and mixed with enzymes and acid until it's a liquid, called chyme. The stomach is the main site for protein digestion and uses powerful enzymes, known as pepsins, as well as hydrochloric acid to digest foods like meats, milk, and cheese.

The small intestine is an approximately 24-foot long muscular tube, which is divided into three distinct parts: the duodenum, jejunum, and ileum. Each of the three parts is a major site of digestion and absorption. Absorption is a crucial part of the digestive system that brings the molecules from the digested food into the blood and, ultimately, the cells.

Problems with your small or large intestine can affect the way your body absorbs and digests food, leading to malnutrition. People who are missing parts of their intestines or have limited intestinal mobility may require total parenteral nutrition (TPN), a type of nutrition which bypasses the digestive system.

The last part of the digestive tract, the large intestine, is a muscular tube that is about 5 feet long. It's divided into the cecum, colon, and rectum. Together, these segments tie up the loose ends of digestion. This includes completing any nutrient absorption and processing the wastes into feces. Your large intestines also make some types of vitamin B and vitamin K.

Problems with your large intestine, colon, and rectum can be caused by diseases such as inflammatory bowel diseases (IBD) like Crohn's disease and ulcerative colitis as well as celiac disease. If part of your colon or rectum does not function the way it is supposed to, you may need an ostomy. 

The pancreas is another necessary digestion-related organ. Your pancreas assists your small intestine by secreting pancreatic juice, a liquid filled with enzymes and sodium bicarbonate that is able to stop the digestion process of pepsin. It also secretes insulin, which helps your body regulate your blood sugar.

Your liver has many functions. First, it produces bile, which the small intestine uses to help digest the fats in food. It also metabolizes proteins, carbohydrates, and fats; helps regulate blood-sugar levels; stores glycogen for quick energy; makes fibrinogen, which clots blood; makes vitamin A; and recycles worn-out red blood cells. 

Diseases of the liver, such as hepatitis, can have major complications that affect other parts of the body as the liver is involved in so many essential functions, like digestion. 

Tucked under the liver, your gallbladder is a storage container for bile, a yellow-green fluid made up of salts, cholesterol, and lecithin. Your small intestine uses gallbladder-produced bile to digest fats.

Most people never think about their gallbladder until a problem with gallstones or gallbladder disease, such as cholecystitis, develops. If you have a gallbladder-related disease, you may experience jaundice. This happens when the bile cannot leave the gallbladder. Instead, the bile enters the bloodstream, which can cause your skin, eyes, and nails to appear yellow.