What is Gastroenterology?

Gastroenterology is the subspecialty of internal medicine that focuses on the diagnosis and treatment of Digestive, Pancreatic, and Liver Diseases. This includes the esophagus, stomach, small intestine, colon or large intestine, rectum and anus, liver, pancreas and biliary tract. 

A Gastroenterologist has advanced medical training in Digestive and Liver Diseases. The Gastroenterologist must first train as an internist, a physician who specializes in internal medicine. After completing a three-year internal medicine residency, the physician completes a three year Gastroenterology Fellowship. It is quite competitive to train in Gastroenterology; therefore only about 25% of all applicants are allowed to enter a Gastroenterology fellowship. 

The competency of the physician is first tested by the Internal Medicine Boards and further evaluated by the Gastroenterology Boards. Passing these rigorous tests enables the physician to become Board Certified. Board eligibility confirms that the physician has completed a residency or fellowship and is eligible to take the National Boards.

During the Gastroenterology Fellowship, the physician is trained in patient care and endoscopy. Endoscopy is the use of flexible fiber-optic instruments to visualize parts of the intestinal tract.

Esophagogastroduodenoscopy views the esophagus and stomach and colonoscopy visualizes the large bowel or colon and the last foot of the small intestine.  Endoscopic retrograde cholangiopancreatography illuminates the pancreatic duct and biliary tree including the gallbladder. 

What does your Digestive System do?
Quite simply, the digestive tract, which includes the mouth and anus and everything in between, is responsible for accepting all the food and liquid you ingest and processing this material for use by all the organ systems in the body. As soon as the food is ingested it is pushed into the stomach where a complex process of breakdown and degradation of food occurs.

Each part of the GI tract is used in its own special way to absorb different types of foodstuffs and nutrients. For example, the small intestine breaks down all the complex sugars in your breakfast cereal to simple sugars which are absorbed and used for energy, repair of damaged tissues, and growth of bones, muscles, etc. The gut or GI tract is roughly 40 feet long and essentially consists of a long hollow tube which not only absorbs food, but contracts to push food along. Once the basic nutrients are absorbed, the leftover material becomes stool; and as we all know, it is excreted from the rectum through the anus.

The Digestive System - (Mouth to Anus)

Oropharynx
Simply, the oropharynx is the area of the throat at the back of the mouth. For Gastroenterologists and of course for the rest of us, this is where the process of digestion begins. While it is well known that oral surgeons and throat surgeons called ENT (ear, nose and throat) Docs deal with diseases of the oropharynx, the Gastroenterologist is quite often asked to evaluate patients who have difficulty swallowing, difficulty with tasting food, and patients with oral ulcers. Therefore, a gastroenterologist must be aware of the anatomy of the mouth and back of the throat and the diseases that affect this area of the body. For the Gastroenterologist, the process of food movement begins in the oropharynx as this part of the body propels the food bolus into the esophagus.

Esophagus
The esophagus is the long muscular tube that connects the oropharynx to the stomach. The esophagus is about a foot long and it looks like a thin garden hose. The food bolus is moved into the top of the esophagus, and then though muscular contractions of the tube called esophageal peristalsis, the food is pushed to the lower end of the esophagus to the junction between the esophagus and stomach. This area is called the gastro esophageal sphincter or lower esophageal sphincter (LES). This sphincter is a “stopcock” which opens to allow the food bolus to empty into the stomach. This muscular “stopcock” occasionally weakens and this is why some people suffer from heartburn or reflux.

Stomach
The stomach is the workhorse of gastrointestinal tract. It receives the food bolus from the esophagus, grinds the food through strong muscular contractions, and prepares the food to be moved into the small intestine for absorption. Our body supplies the stomach with a large amount of acid to help break down the food also. This combination of acid to melt the food and muscular contractions to grind the food helps form an oatmeal consistency of the food in preparation for its movement into the small intestine. The stomach also contains a sphincter called the pylorus which is a “stopcock” preventing food from refluxing back into the stomach once it enters the small intestine. Only water and some medications seem to be absorbed by the stomach because as we know, most food is absorbed in the small intestine.

Small Intestine
The small intestine is also called the midgut. This 30 foot long tube connects the stomach to the colon or large intestine. The small intestine is divided into three parts, the duodenum, the jejunum, and the ileum. The ileum connects to the first part of the large intestine called the cecum. The small intestine has two roles. Its main function is to absorb nutrients from the food, fluid, and digestive enzymes which pass through its lumen. Its other function is to move these nutrients through its lumen, churning the food and digestive juices together. This churning action allows for optimal nutrient breakdown and absorption or digestion. This churning is accomplished by strong muscular contractions, called peristaltic waves, which occur 24 hours a day 7 days a week in your small intestine.

As the food, fluid, and nutrients move down the small intestine they come into contact with tiny finger like projections called villi. These villi increase the surface area of the small intestine and absorption is accomplished much more efficiently. The villi are quite helpful increasing the surface area of the small intestine by over 5000 fold. Once the basic nutrients needed for all your body processes and functions are removed from the small intestine, the left over “paste” is injected into the colon so the water can be removed and feces can beformed.

Colon or Large Intestine
The journey through the colon begins as the “paste” moves through another “stopcock” called the ileocecal valve. Like the other valves throughout the GI tract, this valve prevents the reflux of foodstuff from the large intestine to the small intestine. Once the “paste” enters the cecum it is in the large intestine. The cecum is the first 6 inches of the colon or large intestine. The cecum also houses the opening of the appendix. The appendix is an embryological remnant that serves no function in the human body. Occasional it gets inflamed, this is called appendicitis. Even if you have had your appendix removed we can still see the appendiceal opening from inside the cecum. The entire colon is made up of 6 parts: the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and the rectum. The end of the rectum is the anus, another sphincter which prevents stool from exiting the rectum until you are ready. Without the anal sphincter muscle, life would be quite embarrassing as we would not be able to control when gas or stool would be released. Between the cecum and the rectum is the rest of the colon. These areas are called the ascending colon, the transverse colon, the descending colon, and the sigmoid colon. The ascending colon begins in the right lower abdomen and shoots upwards to the base of the liver under the right ribcage. At the right ribcage, the colon makes a sharp turn called the hepatic flexure. Here is where the transverse colon begins. The transverse colon proceeds across the whole upper abdomen and makes another sharp turn under the left ribcage which is called the splenic flexure. This flexure sits right under the spleen. After the colon moves through this flexure and heads down to the lower abdomen it is called the descending colon. The descending colon makes a quick short “S Curve” just above the rectum called the sigmoid colon. At the end of this curve is the rectum and anus and then of course the outside world.  The six parts of the colon serve mainly one function; to absorb water from the “paste” it receives from the small intestine and form stool or feces. The water is absorbed back into the body through the lining of the colon as the “paste” moves through the length of the 5 foot colon. The colon is shaped like a horseshoe and it surrounds the small intestine. The 30 feet of small intestine are curled up in layers fitting neatly inside the “horseshoe” of the large intestine.

This whole tract from mouth to anus and everything in between is called the gastrointestinal tract and the Gastroenterologist is responsible for diseases that occur along this 40 foot tract or tube. 

When your gastrointestinal tract and all its digestive functions are working normally, you will not be aware of all of these intricate processes. However, sometimes it malfunctions leading to serious and concerning symptoms. That is when you begin to become aware of your gastrointestinal tract. If you have continued gastrointestinal problems, consult your doctor and see a gastroenterological specialist if needed.

Pancreas and Liver
The Gastroenterologist is also responsible to know the intricate workings of two other organs important to digestion: The pancreas and liver. The pancreas sits in the middle of the abdomen surrounded by the stomach and liver. This organ is necessary to aid in the digestive process by sending digestive enzymes or juices to the intestine to aid in digestion. This process is called the “exocrine” function of the pancreas. The pancreas is connected to the small intestine by a tube or duct and the juices flow from the pancreas through this duct to the small intestinal opening called a papilla. This opening shoots these digestive enzymes into the small intestine where they come into contact with the food bolus and begin their work of digestion of the nutrients preparing the nutrients for absorption.  The pancreas also makes insulin to regulate your blood sugar, but that deeply complicated function of the pancreas falls under the realm of an Endocrinologist. The Endocrinologist helps you with problems of “endocrine” function of the pancreas, while the Gastroenterologist can help you with problems of the “exocrine” function of the pancreas. 

The Liver sits in the right upper abdomen below the right rib cage. Its functions include synthesizing bile and blood coagulating factors, acting as the site of metabolism of carbohydrates, proteins and fats, regulating the amount of blood sugar, converting excess glucose to glycogen, removing excess amino acids, storing and metabolizing fats, and detoxifying poisonous substances, worn out red blood cells, and other unwanted material. The liver not only serves to detoxify much of your blood in the body, removing byproducts of the bodies functions such as waste and toxins, but it is responsible for making bile, which is stored in the gallbladder, then is sent to the small intestine to aid in digestion. It is sent to the small intestine via the bile ducts which connect the gallbladder and liver to the gastrointestinal tract. The opening into the small intestine is near the pancreatic duct opening, which has been mentioned above.