The gastric antrum is a specialized, muscular section of the lower stomach. Derived from the Greek word for “cave” or “cavity,” this chamber-like region acts as a processing unit, ensuring food is adequately prepared before moving into the small intestine. It performs both mechanical grinding and chemical regulation necessary for efficient digestion.
Location and Appearance
The gastric antrum is situated at the bottom of the stomach, immediately before the pylorus. It forms a distinct, funnel-shaped structure, with its wider end joining the main body of the stomach, known as the corpus. The narrow end connects to the pyloric canal, which terminates at the pyloric sphincter, the muscular valve controlling entry into the duodenum (the first part of the small intestine).
The antrum’s wall is notably thicker than the upper stomach, reflecting its vigorous function. Its inner lining (mucosa) appears relatively smooth and flat compared to the large folds (rugae) found in the corpus. This robust muscular structure allows the antrum to serve as a high-force mixing and grinding station.
Primary Function in Digestion
The antrum’s function involves powerful mechanical action and precise chemical signaling. Mechanically, it turns solid and semi-solid food into chyme, a uniform, semi-liquid material. This transformation is achieved through intense, rhythmic muscular contractions (peristaltic waves) that grind the food particles. These contractions force the contents against the tightly closed pyloric sphincter.
Only particles smaller than approximately two millimeters pass into the duodenum. Larger material is forcibly pushed back toward the stomach body (retropulsion), ensuring further maceration until the required size is met.
Chemically, the antrum acts as a hormone-producing center, housing specialized G-cells within its lining. These G-cells secrete the peptide hormone gastrin into the bloodstream. Gastrin travels to the upper stomach and stimulates parietal cells to secrete hydrochloric acid. This regulatory loop links the processing activity in the lower stomach to the chemical environment of the upper stomach, controlling overall gastric function.
Common Medical Conditions
The antrum is frequently the site of gastrointestinal issues due to its specific cellular makeup and constant exposure to gastric contents. The most common condition is gastritis, or antral gastritis, which is inflammation of the stomach lining. This inflammation is most frequently linked to colonization by the bacterium Helicobacter pylori.
H. pylori prefers colonizing the antrum, causing chronic inflammation that weakens the mucosal barrier. Persistent inflammation can lead to the formation of peptic ulcers, often referred to as antral ulcers, which are open sores in the stomach lining. Long-term chronic gastritis in this region increases the risk for complications, including gastric polyps or, in rare cases, early-stage gastric cancer.
The antrum is a primary focus during an upper endoscopy, a procedure using a flexible tube and camera to visualize the stomach lining. This inspection allows physicians to detect inflammation, take biopsies to test for H. pylori, and identify structural abnormalities like ulcers or growths.