pylorus

The pylorus is the distal region of the stomach that connects to the duodenum. It includes the pyloric antrum, the pyloric canal, and the pyloric sphincter, a thickened ring of smooth muscle that regulates the passage of stomach contents into the small intestine.

Gastric motility generates peristaltic waves that move chyme toward the pylorus. The pyloric sphincter remains tonically contracted to regulate emptying and relaxes in response to antral contractions, hormonal signals such as gastrin and cholecystokinin, and neural input. In normal function, the rate of gastric emptying is modulated by the composition of the chyme, with fatty and acidic contents slowing transit.

Blood supply to the pyloric region arises mainly from the right gastric and gastroduodenal arteries. Venous drainage follows into the portal system via the gastric and gastroepiploic veins. Lymphatic drainage passes to pyloric nodes and then to the celiac lymph node basin. Autonomic innervation includes parasympathetic fibers from the vagus nerve and sympathetic fibers from the celiac plexus.

Clinical significance includes hypertrophic pyloric stenosis in infants, a condition that causes nonbilious projectile vomiting and dehydration and is treated with pyloromyotomy. In adults, pyloric stenosis or peptic ulcers near the pylorus can cause gastric outlet obstruction and may require surgical or endoscopic intervention.

Etymology: pylorus derives from Greek pyelos, meaning gatekeeper.