20.3: Stomach

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There are four main regions in the stomach: the cardia, fundus, body, and pylorus (Figure \(\PageIndex{1}\)). The cardia (or cardiac region) is the point where the esophagus connects to the stomach and through which food passes into the stomach. Located inferior to the diaphragm, above and to the left of the cardia, is the dome-shaped fundus.

Below the fundus is the body, the main part of the stomach. The funnel-shaped pylorus connects the stomach to the duodenum. The wider end of the funnel, the pyloric antrum, connects to the body of the stomach. The narrower end is called the pyloric canal, which connects to the duodenum. The smooth muscle pyloric sphincter is located at this latter point of connection and controls stomach emptying. In the absence of food, the stomach deflates inward, and its mucosa and submucosa fall into a large fold called a ruga.

This image shows a cross-section of the stomach, and the major parts: the cardia, fundus, body and pylorus are labeled. — Figure \(\PageIndex{1}\): Stomach The stomach has four major regions: the cardia, fundus, body, and pylorus. The addition of an inner oblique smooth muscle layer gives the muscularis the ability to vigorously churn and mix food. (CC-BY-4.0, OpenStax, Human Anatomy)

Histology

The wall of the stomach is made of the same four layers as most of the rest of the alimentary canal, but with adaptations to the mucosa and muscularis for the unique functions of this organ. In addition to the typical circular and longitudinal smooth muscle layers, the muscularis has an inner oblique smooth muscle layer (Figure 20.7). As a result, in addition to moving food through the canal, the stomach can vigorously churn food, mechanically breaking it down into smaller particles.

This diagram shows the histological cross-section of the stomach. The left panel shows the stomach and the center panel shows a magnified view of a small region including the epithelium and the gastric glands. The right panel shows a further magnification of the mucosa and the different cell types are labeled. — Figure \(\PageIndex{2}\): Histology of the Stomach The stomach wall is adapted for the functions of the stomach. In the epithelium, gastric pits lead to gastric glands that secrete gastric juice. The gastric glands (one gland is shown enlarged on the right) contain different types of cells that secrete a variety of enzymes, including hydrochloride acid, which activates the protein- digesting enzyme pepsin. (CC-BY-4.0, OpenStax, Human Anatomy)