Organ
Pyloric sphincter
Muscular regulator at the gastric outlet
High-yield
The pylorus is conventionally projected near L1 in the supine adult, but position varies with posture, filling and body habitus.
Overview
Thickened circular smooth muscle forms the pyloric sphincter between stomach and duodenum. Coordinated activity with the antrum and proximal intestine regulates passage through the outlet. It is a distinct muscular specialization, although the normal pylorus is not ordinarily a palpable abdominal mass.
Reference facts
- Location
- At the distal gastric–proximal duodenal junction, usually to the right of the midline.
- Parts
- Thickened circular muscle around the pyloric canal; a prepyloric vein may provide an external landmark.
- Blood supply
- Right gastric, gastro-omental and gastroduodenal-region branches contribute to a communicating local supply.
- Innervation
- Enteric and extrinsic autonomic pathways coordinate contraction and relaxation with antral and duodenal activity.
- Relations
- Proximal duodenum beyond the outlet, with gastroduodenal vessels posteriorly; lesser and greater omental attachments approach superior and inferior borders.
- Function
- Meters gastric emptying, supports antral grinding by resisting passage of larger particles and limits duodenogastric reflux.
Clinical correlation
Infantile hypertrophic pyloric stenosis narrows the outlet and classically causes progressive nonbilious vomiting because obstruction is proximal to duodenal bile entry. A palpable olive may occur but is not required. Adult outlet obstruction has other causes, including ulcer-related scarring and tumors.
Frequently asked questions
Where is the pyloric sphincter located?
At the distal gastric–proximal duodenal junction, usually to the right of the midline.
What does the pyloric sphincter do?
Meters gastric emptying, supports antral grinding by resisting passage of larger particles and limits duodenogastric reflux.
What are the parts of the pyloric sphincter?
Thickened circular muscle around the pyloric canal; a prepyloric vein may provide an external landmark.
What is the blood supply of the pyloric sphincter?
The pyloric sphincter is supplied by the right gastric, gastro-omental and gastroduodenal-region branches contribute to a communicating local supply.