There are many valves throughout the body that control movement of substances either in one direction only or at times as and when required. Two valves have the same effect in the stomach. It prevents backward flow and allows substances to move in and out of the stomach as desired.
Digestion is a carefully coordinated process to break down food and fluid. This is done mechanically by the way of muscle contractions that crush solids into smaller pieces. It is also achieved chemically by enzymes that digest foods into simpler nutrients. The purpose of digestion is to allow the body to absorb these nutrients where it can then be utilized for various processes.
The stomach is only one organ of digestion. It is part of the upper digestive tract and plays an important role in digestion. The stomach secretes strong hydrochloric acid that breaks down food as well as destroying any microbes in the food. Digestive enzymes are also secreted by the stomach wall which further breaks down the food chemically, The strong muscle contractions of the stomach wall churns the food, fluids and stomach juices.
This digestive activities in the stomach need to be conducted while the inlet and outlet of the stomach is closed.It ensures that the strong muscle contractions do not push the stomach juices up into the esophagus. It also ensures tht the food is crushed into smaller particles. This also ensures that food is not passed out into the small intestine too quickly until it is properly digested, albeit partially, in the stomach.
Types of Stomach Valves
There are two valves that control the inflow and outflow of food and fluids through the stomach. One is located around the lower end of the esophagus. It is technically not a valve in the stomach but does control the movement of food and fluids into the stomach from the esophagus. This valve is also known as the lower esophageal sphincter. It is technically not part of the stomach although it controls movement into the stomach.
The other valve is located at point where the stomach connects to the small intestine. This valve is known as the pyloric sphincter. It controls the flow of partially digested food out of the stomach and into the duodenum (first part of the small intestine). It is also part of the end portion of the stomach which acts like a pump to move stomach contents out but also ensures that large food particles remain for further digestion.
Problems with Lower Esophageal Sphincter
The lower esophageal sphincter (LES) is made up of smooth muscle arrange in circular manner around the end of the esophagus. Normally the sphincter remains closed and only opens for short periods to allow food that is swallowed to enter the esophagus from the stomach. The term lower esophageal sphincter (LES) dysfunction to a number of conditions where the sphincter may not open or close as normal.
Signs and symptoms of LES problems may include:
- Nausea and vomiting
- Regurgitation of food
- Bloated feeling
- Heartburn and sometimes other types of chest pain
Only some of the more likely conditions that arise with lower esophageal sphincter (LES) dysfunction has been discussed below.
Gastroesophageal Reflux Disease
GERD is the most common condition that arises with lower esophageal sphincter (LES) dysfunction. It is a conseqeunce of LES failure. The valves failure to close properly allows the stomach juices to flow backward into the esophagus. It causes irritation and inflammation of the esophagus and the most common symptom is heartburn (burning chest pain). Reflux is worse after eating and when lying flat.
Achalasia is an uncommon condition where the lower esophageal sphincter does not open to allow food into the stomach. In addition the muscles of the esophagus responsible for pushing food down the esophagus may also weaken. This causes food and fluid to become backed up in the esophagus. Achalasia is a result of damage to the nerves that supply the muscles of the lower esophageal sphincter (LES). Cancer may also be responsible.
Problems with Pyloric Sphincter
The pyloric sphincter regulates flow of contents out of the stomach and into the duodenum of the small intestine. Similar to the lower esophageal sphincter (LES), it is composed of a circular band of muscle. It works in conjunction with the muscles of the pylorus that push the food and fluid mixture (gastric chyme) out of the stomach. Larger food particles may not be passed through until it is further broken down by the stomach.
Signs and symptoms include:
- Regurgitation and sometimes vomiting
- Bloated feeling
- Upper left and upper middle abdominal pain
- Heartburn or chest pain (sometimes)
- Diarrhea (sometimes)
Only some of the more likely conditions that arise due to pyloric sphincter problems have been discussed below.
Gastroparesis is a condition where the nerves controlling the stomach muscles may become diseased or damaged. As a result this leads to a delay in the emptying of the stomach. There is no physical obstruction like a tumor. Instead the pyloric sphincter may not open properly and the stomach does not crush and push food as it should. Diabetes-related nerve damage, certain drugs and nerve damage due to surgery are some of the causes.
Pyloric stenosis is where there is a narrowing of the end portion of the stomach due to a thickening of the muscles in this area. It arises in infants and may be present from birth. The growth of the muscles that make up the sphincter may not be accompanied with proper nerve supply development. As a result some of these muscle fibers may not be controlled by the nervous system and this can affect sphincter function.
Gastric Dumping Syndrome
Dumping syndrome is where the outflow of stomach contents cannot be controlled. It is mainly due to stomach surgery and specifically gastric bypass procedures. These procedures compromise the pyloric sphincter’s ability to control flow. It can also occur with damage of the stomach nerve. The stomach contents are rapidly emptied into the small intestine before it can be properly digested.