Atresia is the absence or marked narrowing of the lumen (the passage inside) of the gut (gastrointestinal tract) at birth. It may occur at any point in the gut.

Pyloric Atresia

Anatomy and Physiology

The stomach is a C-shaped organ that lies under the left lower ribs and upper part of the abdomen.

• The stomach is divided into three parts (Figure 1):
  
  1. The cardia is the portion of the stomach that is adjacent to the esophagus
     
  2. The body of the stomach is the largest part and has two curvatures, the lesser curvature, which lies on the inside of the C, and the greater curvature, which lies on the outside of the C
     
  3. The pylorus lies at the end of the stomach
     
• Food entering the mouth is passed into the esophagus and then goes into the upper end of the stomach. The stomach holds and mixes the food with gastric (stomach) juices that aid in digestion and then passes the mixture through the pylorus, a muscular sphincter or gate, that controls the passage of the stomach contents into the duodenum, which is the beginning of the small bowel

Figure 1 - Sectional anatomy of the stomach demonstrating the pylorus. © P. Montelone