What Is the Function of the Pyloric Sphincter?
It is estimated that 11% of the population of the United States has a chronic digestive disease, and that includes up to 35% of those who are 65 years or older. Moreover, digestive diseases are responsible for around one quarter of all surgeries. It is one of the most common reasons for people to be hospitalized. Because the digestive system is so complex and central to many aspects of health, there are many ways that problems can manifest. One part of the digestive system that can be a source of problems is the pyloric sphincter.
Location of the Pyloric Sphincter
The digestive tract is a long line of organs that runs from the mouth to the anus, and its purpose is to extract nutrients and energy from foods and eliminate waste. After food is chewed and swallowed, it travels down the esophagus toward the stomach. At the top part of the stomach (cardia, followed by the fundus), the lower esophageal sphincter allows food in and simultaneously keeps stomach contents from backing up into the esophagus (known as regurgitation). While the food is there, it is subjected to gastric juices and the process of peristalsis in order to break it down and prepare it to be absorbed in the small intestine.
Before this partially digested food reaches the small intestine, though, it must pass through the pylorus. The pylorus is a hollow structure that connects the stomach to the first part of the small intestine, the duodenum. The pylorus has two parts: the first part is the pyloric antrum and the second part is the pyloric canal. The pyloric sphincter is a ring of smooth muscle at the end of the pyloric canal that allows food to pass into the duodenum and begin the next phase of the digestive process.
Function of the Pyloric Sphincter
The GI tract has several sphincter muscles that all perform a similar function; these smooth circular muscles act as gateways between different parts of the system so that food enters the next section at the appropriate time. The pyloric sphincter plays an important role in digestion because it allows food to pass into the small intestine only after it has sufficiently been broken down. Once the partially digested food (chyme) enters the small intestine, enzyme-rich pancreatic juices break down into components that can be absorbed by the mucosa that surrounds the intestinal lumen.
In addition to allowing food to pass into the duodenum, the pyloric sphincter also prevents undigested food from entering too early. The process of peristalsis in the stomach involves strong contractions that would otherwise force contents into the small intestine before they were fully processed. The pyloric sphincter opens just enough so that small amounts of chyme can enter without larger solids. Similarly, as the duodenum fills, it can cause pressure to build, and the pyloric sphincter also prevents materials from backing up into the stomach.
Conditions that Affect the Pyloric Sphincter
In normal circumstances, the pyloric sphincter works smoothly with the other organs in the gastrointestinal system to move food through a staged digestive process. For most healthy people, they’re barely aware of this happening (apart from an occasional gurgling noise perhaps). But if the pyloric sphincter is damaged or isn’t working properly, it can cause a number of problems or digestive abnormalities. Below are some conditions that may be related to problems with the pyloric sphincter:
- Pyloric stenosis: Hypertrophic pyloric stenosis involves a thickening of the tissue of the pylorus and a subsequent narrowing of the pyloric canal. This condition is almost exclusively found in infants, though it can also occasionally occur in older children. The cause is still unknown, but there are likely both environmental and genetic factors that make a baby more susceptible. Projectile vomiting shortly after feeding is the most common symptom, and it is due to food not being able to get through the narrowed pylorus.
- Gastroparesis: Also known as delayed gastric emptying, gastroparesis is a disorder in which the muscles of the stomach involved in peristalsis are weakened. This results in solids and liquids remaining in the stomach for longer than normal. The delay in gastric emptying can lead to inadequate absorption of nutrients. Also, the disruption to the normal metabolism of glucose can cause significant problems for glycemic control; among other concerns, this can worsen diabetes and other blood sugar-related conditions.
- Biliary reflux: Bile secretions normally enter the duodenum where they are used by the body to break down chyme prior to traveling through the small intestine. The pyloric sphincter prevents bile from backing up into the stomach. However, if the pyloric sphincter is damaged or malfunctioning, it can enter the stomach and then further back up into the esophagus. A small amount of bile in the stomach is normal, but at higher concentrations it can cause inflammation; it can even potentially lead to gastritis, ulcers, or gastric cancer.
- Cancer: Stomach cancer can develop in any part of the stomach, including the pylorus. Yet even if a cancerous tumor develops outside the pyloric canal, it can still potentially cause an obstruction that can lead to delayed gastric emptying or other problems.
Depending on the nature of the problem in the pylorus, treatment may involve dietary changes, medication, or surgery. Cases of pyloric stenosis are almost always treated with surgery through a procedure (pyloromyotomy) that divides the thickened outer muscle. Treatment for gastroparesis typically involves switching to a low-fiber diet and medications that are stimulators for the sphincter muscle. For a condition like biliary reflux, the treatment is more of a management strategy to neutralize the bile that makes it into the stomach. Stomach cancer is one of the more dangerous forms of cancer, unfortunately, and it may require surgery, chemotherapy, or radiation depending on the stage.
When to Contact a Doctor of Gastroenterology
Problems with the pyloric sphincter can have obvious or non-obvious symptoms, so it’s difficult to know without a diagnosis from a gastroenterologist. In general, though, it’s important to be mindful of symptoms and changes to bowel habits; these can be alerts that an examination is necessary. If you’ve been experiencing any of the symptoms above or any other gastrointestinal distress, please contact us at Cary Gastro to request an appointment. We are dedicated to providing excellent healthcare for maximum quality of life and peace of mind.