Organ
Lower esophageal sphincter
Intrinsic smooth-muscle barrier supported by the crura
High-yield
Intrinsic smooth-muscle tone and crural contraction are complementary parts of the antireflux barrier. Swallowing activates a vagal–enteric pathway that relaxes the intrinsic muscle.
Overview
The lower esophageal sphincter is a tonically active smooth-muscle region at the gastroesophageal junction. It is identified physiologically as a high-pressure zone rather than as a conspicuous pylorus-like ring. The crural diaphragm, junctional geometry and intra-abdominal esophageal segment add external support to the intrinsic sphincter.
Reference facts
- Location
- At the distal esophageal/gastric junction, normally closely aligned with the diaphragmatic hiatus and partly within the abdomen.
- Parts
- Specialized distal smooth muscle forms the intrinsic high-pressure region; phrenoesophageal attachments and the crural diaphragm support its position and function.
- Blood supply
- Distal esophageal and cardial branches, particularly from the left gastric and inferior phrenic arterial territories.
- Innervation
- Preganglionic vagal fibers influence myenteric neurons; inhibitory enteric motor neurons release nitric oxide, while excitatory pathways help maintain or restore contraction.
- Relations
- The crural diaphragm surrounds the hiatus, chiefly through right-crural fibers, and normally overlaps the junctional high-pressure region.
- Function
- Limits gastric reflux during resting tone and relaxes for swallowed material and physiological venting such as belching.
Clinical correlation
A sliding hiatal hernia can separate the intrinsic sphincter from diaphragmatic support and promote reflux, although many hernias cause no symptoms. Paraesophageal and mixed hernias have different anatomical arrangements and can produce mechanical complications such as volvulus.
Frequently asked questions
Where is the lower esophageal sphincter located?
At the distal esophageal/gastric junction, normally closely aligned with the diaphragmatic hiatus and partly within the abdomen.
What does the lower esophageal sphincter do?
Limits gastric reflux during resting tone and relaxes for swallowed material and physiological venting such as belching.
What are the parts of the lower esophageal sphincter?
Specialized distal smooth muscle forms the intrinsic high-pressure region; phrenoesophageal attachments and the crural diaphragm support its position and function.
What is the blood supply of the lower esophageal sphincter?
The lower esophageal sphincter is supplied by the distal esophageal and cardial branches, particularly from the left gastric and inferior phrenic arterial territories.