The Gut

The digestive system is a group of organs working together to convert food into energy and basic nutrients to feed the entire body. Food passes through a long tube inside the body known as the alimentary canal or the gastrointestinal tract (GI tract). The alimentary canal is made up of oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine (colon). In addition to the alimentary canal, there are several important accessory organs that help your body digest food but do not have food pass through them. Accessory organs of the digestive system include salivary glands, liver, gallbladder, and pancreas.

gastroenterologist is a physician who specializes in diseases of the digestive system, also called the gastrointestinal tract.  Gastroenterologists may be involved with the diagnosis, the treatment, and the overall management of conditions affecting the GI tract.

Understanding the GI Tract

Food begins its journey through the digestive system in the mouth. Teeth chop food into small pieces, which are moistened by saliva before the tongue and other muscles push the food further down the GI tract to the esophagus.

The esophagus is the muscular tube that conveys food from the back of the throat to the stomach. It is located in the chest behind the sternum and the trachea, the main breathing tube leading to the lungs. The esophagus joins the stomach at the diaphragm, which is the breathing muscle separating the chest and lungs from the abdomen. The connection of the esophagus to the stomach at the diaphragm is called the gastro-esophageal junction (or GE junction). A ring of muscle fibers called the "lower esophageal sphincter" is located at the level of the gastro-esophageal junction. It serves as a one-way valve to keep stomach contents from being refluxed or regurgitated back into the esophagus.

The stomach is a muscular sac that is located on the left side of the abdominal cavity, just below the ribs. In an average person, the stomach is about the size of their two fists placed next to each other. This major organ acts as a storage tank for food so that the body has time to digest large meals properly. The stomach also produces hydrochloric acid and some digestive enzymes that continue the digestion of food which began in the mouth.

Small Intestine
The small intestine is a long, thin tube about 1 inch in diameter and about 20-25 feet long. It is located just below the stomach and takes up most of the space in the abdominal cavity. The entire small intestine is coiled like a hose and the inside surface is full of many ridges and folds. These folds are used to maximize the digestion of food and absorption of nutrients. By the time food leaves the small intestine around 90% of all nutrients have been extracted from the food that entered it.

The liver is a very important organ of the digestive system located to the right of the stomach, just below the ribs. The liver weighs about 3 pounds and is the second largest organ in the body. The liver has many different functions in the body, but the main function of the liver in digestion is the production of bile and its secretion into the small intestine.

Gallbladder & Bile Ducts 
The gallbladder is a small, pear-shaped organ located next to and behind the liver. The gallbladder is used to store and recycle excess bile from the small intestine so that it can be reused for the digestion of subsequent meals.

The pancreas is a glandular organ located in the posterior aspect of the abdomen. It lies between the liver and the spleen, and just below and behind the stomach. The pancreas produces digestive enzymes (exocrine function), which are emptied into the small bowel, as well as the hormone insulin (endocrine function), which enters the blood stream.

Colon or Large Intestine
The colon is a long, thick tube about 3-5 feet long. It is located just below the stomach and connects the small intestine to the rectum. The large intestine absorbs water and contains many bacteria that aid in the breaking down of wastes to extract some small amounts of nutrients. Feces in the large intestine exit the body through the anal canal.