What is the primary role of the lower esophageal sphincter in the gastrointestinal system?
Solution
Correct Answer: Option B
- The lower esophageal sphincter (LES) plays a crucial role in the gastrointestinal system by acting as a barrier between the esophagus and the stomach.
- Its primary function is to prevent the backflow (reflux) of gastric contents, including acidic stomach acid, into the esophagus.
- This is important because the lining of the esophagus is not adapted to withstand the corrosive effects of stomach acid, and reflux can lead to irritation or damage, commonly known as gastroesophageal reflux disease (GERD).
- The LES achieves this by maintaining a tonic contraction that closes off the esophagus from the stomach when food is not being swallowed. When swallowing occurs, the sphincter momentarily relaxes to allow food to pass into the stomach and then quickly closes again.
To clarify the other options:
- Option 1: The passage of bile into the stomach is not a function of the LES; bile is secreted into the small intestine, primarily through the bile duct.
- Option 3: The LES does not regulate pancreatic enzyme release; this is controlled by hormones such as secretin and cholecystokinin.
- Option 4: Nutrient absorption primarily occurs in the small intestine, and the lower esophagus does not play a significant role in nutrient absorption.
Therefore, the correct role of the lower esophageal sphincter is to prevent the backflow of gastric acid into the esophagus.
Reference: Robbins Basic Pathology, 10th Edition, Chapter 25: Esophagus — Page 1107
- Its primary function is to prevent the backflow (reflux) of gastric contents, including acidic stomach acid, into the esophagus.
- This is important because the lining of the esophagus is not adapted to withstand the corrosive effects of stomach acid, and reflux can lead to irritation or damage, commonly known as gastroesophageal reflux disease (GERD).
- The LES achieves this by maintaining a tonic contraction that closes off the esophagus from the stomach when food is not being swallowed. When swallowing occurs, the sphincter momentarily relaxes to allow food to pass into the stomach and then quickly closes again.
To clarify the other options:
- Option 1: The passage of bile into the stomach is not a function of the LES; bile is secreted into the small intestine, primarily through the bile duct.
- Option 3: The LES does not regulate pancreatic enzyme release; this is controlled by hormones such as secretin and cholecystokinin.
- Option 4: Nutrient absorption primarily occurs in the small intestine, and the lower esophagus does not play a significant role in nutrient absorption.
Therefore, the correct role of the lower esophageal sphincter is to prevent the backflow of gastric acid into the esophagus.
Reference: Robbins Basic Pathology, 10th Edition, Chapter 25: Esophagus — Page 1107
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