The stomach is located in the upper part of the abdomen just beneath the diaphragm (Figure 1). The stomach is distensible and on a free mesentery, therefore, thesize, shape, and position may vary with posture and content. An empty stomach is roughly the size of an open hand and when distended with food, can fill much of the upper abdomen and may descend into the lower abdomen or pelvis on standing. The duodenum extends from the pylorus to the ligament of Treitz in a sharp
curve that almost completes a circle. It is so named because it is about equal in length to the breadth of 12 fingers, or about 25 cm. It is largely retroperitoneal and its position is relatively fixed. The stomach and duodenum are closely related in function, and in the pathogenesis and manifestation of disease.The stomach may be divided into seven major sections. The cardia is a 1–2 cm segment distal to the esophagogastric junction. The fundus refers to the superior portion of the stomach that lies above an imaginary horizontal plane that passes through the esophagogastric junction. The antrum is the smaller distal one-fourth to one-third of the stomach. The narrow 1–2 cm channel that connects the stomach and duodenum is the pylorus. The lesser curve refers to the medial shorter
border of the stomach, whereas the opposite surface is the greater curve. The angularis is along the lesser curve of the stomach where the body and antrum meet, and is accentuated during peristalsis
The duodenum extends from the pylorus to the ligament of Treitz in a circle-like curve and is divided
into four portions. The superior portion is approximately 5 cm in length, beginning at the pylorus, and passes beneath the liver to the neck of the gallbladder. The first part of the superior portion (2–3 cm) is the duodenal bulb. Thedescending or second part of the duodenum takes a sharp curve and goes down along the right margin of the head of the pancreas. The common bile duct and the
pancreatic duct enter the medial aspect of this portion of the duodenum at the major papilla either separately or together. The duodenum turns medially, becoming the horizontal portion, and passes across the spinal column, inclining upward for 5–8 cm. The ascending portion begins at the left of the spinal column, ascending left of the aorta for 2–3 cm, and ends at the ligament of Treitz, where the intestine angles forward and downward to become the jejunum.