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The lower esophageal sphincter (LES) is a bundle of involuntary muscles that sit at the bottom of the esophagus, where it meets the stomach. The LES is a high-pressure zone that protects the esophagus from the reflux of gastric contents. It is composed of intrinsic and extrinsic components. The intrinsic component consists of smooth muscle fibers that are under neurohormonal control, while the extrinsic component consists of the diaphragmatic crura and the phrenoesophageal ligament, which provide anatomical support and further protection against gastric reflux. The LES is sometimes referred to as the gastroesophageal sphincter or cardiac sphincter due to its proximity to the stomach and heart. Its primary function is to prevent stomach acid and food from flowing back up into the esophagus, and dysfunction of the LES can lead to acid reflux and gastroesophageal reflux disease (GERD).
| Characteristics | Values |
|---|---|
| Location | Where the oesophagus meets the stomach |
| Composition | Intrinsic and extrinsic components |
| Intrinsic component | Esophageal muscle fibres, smooth muscle |
| Extrinsic component | Diaphragmatic crura, phrenoesophageal ligament |
| Function | Protects oesophagus from reflux of gastric contents, prevents food from flowing back up the oesophagus |
| Control | Neurohormonal, involuntary |
| Dysfunction | Acid reflux, gastroesophageal reflux disease (GERD), achalasia |
| Treatment | Baclofen, botulinum toxin (Botox), breathing exercises |
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What You'll Learn
The lower esophageal sphincter (LES) is a bundle of involuntary muscles
The primary function of the LES is to prevent acid and food in the stomach from rising back up into the oesophagus or throat. When food reaches the throat, the LES opens to allow food to pass through to the stomach. The LES remains open for about five seconds after swallowing, and then closes to keep food and digestive enzymes from washing back up. When the LES does not close tightly enough, stomach acid and food particles can rise back up into the oesophagus, causing acid reflux. Acid reflux can lead to gastroesophageal reflux disease (GERD), in which the oesophagus is irritated by stomach acid or bile.
A structurally defective LES is a significant factor in the development of reflux disease. In individuals with a hiatal hernia, the new position of the LES may prevent complete closure, allowing for increased backflow of digestive juices, heartburn, and oesophageal damage. Hypertensive LES involves increased muscle contraction, and its symptoms tend to worsen over time. Treatments for a weak LES include muscle relaxants and myotomy, a minimally invasive surgery. Botox can also be injected into the LES to relax the sphincter.
Breathing exercises have been shown to strengthen the diaphragm and reduce reflux over time. Leg raises, in particular, have been found to increase pressure in the LES.
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The LES is composed of intrinsic and extrinsic components
The lower esophageal sphincter (LES) is a bundle of involuntary muscles that contract and move without conscious control. The LES is located where the lower end of the oesophagus meets the stomach. The primary function of the LES is to prevent acid and food in the stomach from rising back up into the oesophagus or throat.
The extrinsic component of the LES consists of the diaphragmatic crura and the phrenoesophageal ligament, which provide anatomical support to the LES and further protection against gastric reflux. The LES is a high-pressure zone that protects the oesophagus from the reflux of gastric contents. Any malfunction in either the intrinsic or extrinsic components can lead to pathologies such as gastroesophageal reflux disease (GERD), with associated symptoms and mucosal changes.
The LES is involved in the proper transport of ingested contents into the stomach. Relaxation of the LES and the diaphragmatic sphincter occurs during swallowing and the distension of the oesophagus. Swallowing-induced LES relaxation is mediated by the release of VIP and NO and lasts for approximately 6 to 10 seconds. The LES remains open for about five seconds after swallowing, allowing food to enter the stomach. It then closes to prevent food and digestive enzymes from washing back up into the oesophagus.
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The LES opens to allow food to flow into the stomach
The lower esophageal sphincter (LES) is a bundle of involuntary muscles that are not under conscious control. It is located at the lower end of the oesophagus, where the oesophagus meets the stomach. The oesophagus is a muscular tube that connects the mouth to the stomach and is about 8 to 10 inches long. It has a sphincter at each end, the upper esophageal sphincter (UES) and the LES.
Once food has passed through the UES, the muscles in the oesophagus use a wavelike motion, or peristaltic wave, to push food downward and through the LES to the stomach. The LES stays open for about five seconds after swallowing, then closes to keep food and digestive enzymes from washing back up into the oesophagus. The LES prevents food from flowing back up the oesophagus and protects the oesophagus from the reflux of gastric contents.
The LES is composed of intrinsic and extrinsic components. The intrinsic component consists of smooth muscle fibres that keep the sphincter tightly contracted. The extrinsic component consists of the diaphragmatic crura and the phrenoesophageal ligament, which provide anatomical support to the LES and further protection against gastric reflux.
The LES can sometimes malfunction, leading to pathologies such as gastroesophageal reflux disease (GERD). This occurs when the LES does not close tightly enough, allowing stomach acid and food particles to rise back up into the oesophagus.
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Acid reflux occurs when the LES opens when it's not supposed to
The lower esophageal sphincter (LES) is a bundle of involuntary muscles that sits at the bottom of the esophagus, where it meets the stomach. The LES is also called the gastroesophageal sphincter or gastroesophageal junction because of the two structures it connects. The primary function of the LES is to keep food, stomach acid, and digestive juices in the stomach from rising back up into the throat.
The LES usually stays shut when there is no food or liquid passing through it. When food is swallowed, the LES relaxes or opens to allow food to move down into the stomach. The LES stays open for about five seconds after swallowing and then closes to keep food and digestive enzymes from washing back up into the esophagus.
Acid reflux occurs when the LES opens when it is not supposed to. This can be due to a malfunction in either the intrinsic or extrinsic components of the LES. The intrinsic component of the LES consists of smooth muscle that keeps the sphincter tightly contracted. Direct inhibitory signals allow the smooth muscles in the LES to relax, opening the sphincter and enabling the passage of food. The extrinsic component consists of the diaphragmatic crura and the phrenoesophageal ligament, which provide anatomical support to the LES and further protection against gastric reflux. When the LES doesn't close tightly enough or becomes weakened, stomach acid and digestive juices can flow back into the esophagus, causing acid reflux.
Acid reflux is characterized by a burning sensation in the chest or throat, known as heartburn. Heartburn can be triggered by consuming spicy or acidic foods, large meals, or lying down or bending over soon after eating. Acid reflux can also cause other symptoms such as chest pain, hoarseness, bad breath, and trouble swallowing. If left untreated, acid reflux can lead to significant damage to the esophagus, including inflammation, scar tissue formation, and precancerous changes.
Treatment options for acid reflux include lifestyle changes, over-the-counter medications, prescription medications, and surgery. Lifestyle changes include avoiding trigger foods, eating smaller and more frequent meals, and waiting a few hours after eating before lying down. Over-the-counter medications such as antacids can help neutralize stomach acid and relieve symptoms. If these treatments are ineffective, prescription medications such as proton pump inhibitors or prokinetic agents may be recommended to reduce acid production or tighten the LES muscle. In severe cases of acid reflux or gastroesophageal reflux disease (GERD), surgery may be considered to strengthen the LES and prevent acid reflux.
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Hypertensive LES involves increased muscle contraction
The lower esophageal sphincter (LES) is a bundle of involuntary muscles that contract without conscious control. The LES is located at the opening of the lower esophagus, where the esophagus meets the stomach. It acts as a valve, opening to allow food to pass into the stomach and remaining closed to prevent the backflow of stomach acid and digestive juices into the esophagus.
Vascular smooth muscle cells, which constitute the majority of the vascular wall, play a critical role in these processes. They undergo phenotypic changes from a contractile to a proliferative state, leading to increased vascular contraction. This increased contraction is triggered by an increase in intracellular free calcium concentration, which promotes actin–myosin cross-bridge formation. Additionally, calcium-independent mechanisms, such as RhoA-Rho kinase signalling, protein kinase C activation, and increased reactive oxygen species, also contribute to the regulation of vascular contraction in hypertension.
The treatment for hypertensive LES often involves myotomy, a minimally invasive surgical procedure similar to that used for achalasia. This procedure helps alleviate the increased muscle contraction associated with hypertensive LES and improves the function of the lower esophageal sphincter.
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Frequently asked questions
The lower esophageal sphincter (LES) is a bundle of involuntary muscles that open to allow food to flow into the stomach.
The primary function of the LES is to keep the acid and food in your stomach from coming back up into your throat.
When the LES doesn't close tightly enough, it can cause acid reflux, where stomach acid and food particles rise back up into the oesophagus. This can lead to gastroesophageal reflux disease (GERD), which causes symptoms such as heartburn, chest pain, and hoarseness.
The LES opens and closes based on the body's needs. Swallowing and distention of the oesophagus are the two major stimuli that induce relaxation of the LES, allowing food to pass through.
Yes, some studies suggest that breathing exercises to strengthen the diaphragm can help reduce reflux. Additionally, procedures such as laparoscopic antireflux surgery can strengthen the LES by creating a new valve device at the bottom of the oesophagus.
