CHAPTER 9: Foregut

GI PORTION OF THE FOREGUT

BIG PICTURE

The foregut consists of the distal end of the esophagus, stomach, duodenum (first and second parts), pancreas, liver, and gallbladder. The celiac trunk is the primary arterial supply of the foregut and the portal vein provides its venous drainage. Lymph from the foregut drains into the celiac nodes surrounding the celiac trunk.

ESOPHAGUS

The esophagus traverses the diaphragm to enter the abdominal cavity at the T10 vertebral level where the esophagus transitions immediately into the stomach. The cardiac sphincter serves as the transition boundary between esophagus and stomach.

GERD. A function of the stomach is the production of hydrochloric acid. If the cardiac sphincter fails to contain the acidic chyme produced by the stomach, the acid moves into the esophagus, irritating its mucosal lining and causing gastroesophageal reflux disease (GERD). The irritation presents as an uncomfortable, perhaps burning, sensation in the region of the esophagus, deep to the heart. As a result, this condition is also referred to as “heart burn.”▼

STOMACH

The stomach is a dilated portion of the foregut between the esophagus and duodenum (Figure 9-1A and B).

• Topography. The stomach is located in the upper left quadrant of the abdomen and is superficial to the spleen, pancreas, and aorta.

• Function. Peristaltic movements churn gastric contents, facilitating their breakdown and mixing in secretions from gastric glands.

  • Gastric secretions. Include pepsin (digests proteins) and gastric lipase (digests lipids); the stomach churns food contents and gastric secretions into chyme, which is transported to the duodenum.

• Regions. The stomach has the following regions:

  • Cardia. Surrounds the gastroesophageal opening into the stomach.

  • Fundus. Dome-shaped region superior to the cardia.

  • Great curvature. The longer, inferior region of the stomach.

  • Lesser curvature. The shorter, superior region of the stomach.

  • Body. Largest stomach region.

  • Pylorus. Distal region of the stomach, which lies at the L1 vertebral level (transpyloric plane).

  • Pyloric sphincter. A thick circular layer of smooth muscle that controls the passage of gastric contents into the duodenum.

  • Gastric rugae. Folds along the internal surface of the stomach that increases surface area and channels chyme toward the duodenum. The gastric rugae disappear when the stomach fills (can hold up to 1.5 L of food).

• Peritoneum. The stomach is covered externally by the peritoneum that is the transition between the lesser omentum and greater omentum.

Hiatal hernia. The distal end of the esophagus and gastric fundus can herniate through the esophageal hiatus of the diaphragm into the thoracic cavity. This is known as a hiatal hernia and results from conditions such as long-term ...