The pylorus is the outlet of the stomach, a thick-walled region surrounding the pyloric orifice where the stomach opens into the duodenum. Its circular muscle is greatly thickened to form the pyloric sphincter. It usually lies on the transpyloric plane at about L1, just right of the midline.
| Location | Distal end of the stomach at about L1 (transpyloric plane), just right of the midline, continuous with the first part of the duodenum |
|---|---|
| Parts |
|
| Nerve Supply | Anterior and posterior vagal trunks; Coeliac plexus (sympathetic) |
| Blood Supply | Right gastric artery; Right gastro-omental artery; Supraduodenal and gastroduodenal branches |
| Venous drainage |
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| Lymphatic drainage |
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Regulates the passage of chyme into the duodenum in small amounts and limits reflux of bile and duodenal contents into the stomach.
The prepyloric vein, crossing the front of the pylorus, helps surgeons find it during operations. In infants a few weeks old, overgrowth of the pyloric muscle causes forceful non-bilious vomiting and a palpable olive-shaped mass, treated by pyloromyotomy. In adults, scarring from ulcers or cancer near the pylorus can obstruct gastric emptying.
Thickening of the pyloric muscle in infants, typically 2-8 weeks old, causing projectile vomiting, dehydration and hypochloraemic metabolic alkalosis.
Peptic ulcer at the pylorus that can cause pain soon after eating and may scar to obstruct the outlet.
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