Stenosis (narrowing) of the pylorus or duodenum may occur in infants resulting in obstruction of the stomach or duodenum to the passage of food.

Pyloric Stenosis

Anatomy

• The stomach is arbitrarily divided into three parts (Figure 1):
  
  1. The cardia is the part 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 is the part of the stomach that lies at the end of the stomach and is demarcated from the body by a difference in the type of glands from those in the body. The pyloric canal is the narrow segment of the pylorus that approaches the pyloric sphincter
     
• The wall of the stomach is divided into four layers
  
  1. The mucosa is the inner layer and contains the glands that produce the gastric juice
     
  2. The submucosa is a thin layer lying just beneath the mucosa
     
  3. The muscularis is the muscle layer that has an inner circular portion and an outer layer that runs the length of the stomach
     
  4. The serosa is the outer layer of the stomach

Figure 1 - Sectional anatomy of the pylorus showing the stomach, pylorus and duodenum. © P. Montelone