The stomach, a muscular organ located in the upper abdomen, plays a significant role in the initial stages of digestion. It acts as a temporary reservoir for food, breaking it down both mechanically and chemically before it moves into the small intestine. This organ is more complex than a simple pouch, featuring distinct regions that work together to process ingested food.
The Stomach’s Major Regions
The stomach is divided into several anatomical regions, each with a specific function in the digestive process. The first part, the cardia, surrounds the entry point where the esophagus connects to the stomach. This area contains a sphincter that prevents food and stomach acid from flowing back into the esophagus.
Following the cardia is the fundus, a rounded, dome-shaped section situated to the left and above the cardia. The body, also known as the corpus, represents the largest and central part of the stomach. This is where most of the mixing and initial breakdown of food occurs.
The stomach then narrows into the pyloric part, which is further subdivided. This final section connects the stomach to the small intestine. The pylorus includes the antrum, the pyloric canal, and the pyloric sphincter, which regulate the passage of digested food.
Locating the Gastric Antrum
The gastric antrum, also known as the pyloric antrum, is located in the distal portion of the stomach. It lies directly below the main body of the stomach. This region is the wider, initial segment of the pylorus.
The antrum is funnel-shaped, with its broader end connecting to the stomach’s body. Its narrower end leads into the pyloric canal, which then connects to the duodenum, the first part of the small intestine. This positioning makes the antrum a transitional zone within the digestive tract.
The pyloric canal is a narrow passage that acts as the inferior terminal segment of the antrum. The antrum thus sits just before the final muscular ring, the pyloric sphincter, which controls emptying into the small intestine.
Role of the Gastric Antrum
The gastric antrum performs functions in the digestive process. Its muscular walls contract rhythmically, churning and grinding food particles. This mechanical action, known as peristalsis, breaks down food and thoroughly mixes it with gastric juices, forming a semi-liquid substance called chyme.
Beyond mechanical mixing, the antrum also contributes to chemical digestion and regulating gastric emptying. It contains specialized glands that secrete mucus and hormones. Among these are G-cells, which are found deep within the pyloric glands of the antrum.
These G-cells produce gastrin, a hormone that stimulates the secretion of hydrochloric acid by other cells in the stomach. Gastrin also aids in gastric motility and strengthens antral contractions, which propel chyme through the pyloric sphincter and into the small intestine.