The stomach is a hollow, muscular, pear-shaped organ situated in the upper abdomen and connected to the oesophagus at one end and the duodenum (first section of the small intestine) at the other end. It also forms the most dilated portion of the alimentary tract, although the stomach's size, shape and position show considerable variations, depending upon a person's build and posture. In order to understand why your stomach gurgles after you eat, however, you need some knowledge of the digestive process and the stomach's two main functions.
The process of digestion consists of both chemical and physical changes as food passes from your mouth to your stomach and then into your intestines. The chemical change involves the breakdown of swallowed food into smaller, more soluble molecules. The physical change involves the rhythmic contractions of both the stomach and the intestines, and these contractions serve to mix consumed food with secretions from various portions of the digestive tract.
When you ingest food, it is saturated with salivary secretions, first in your mouth to a lesser degree, then in your stomach to a greater degree, and this action continues until checked by the acidity of the stomach's gastric juice, which contains from 0.4 to 0.5 per cent hydrochloric acid, as well as chlorides of sodium and potassium, nitrogenous elements and phosphates. This gastric juice softens the cellulose fibres in whatever you have ingested and initiates the digestion of proteins, converting them to peptones.
The stomach's motor function consists of periods of activity that create peristaltic waves (rhythmic motions consisting of alternating contractions) that, in small portions, churn and macerate (soften and break down) whatever food has been ingested and help prepare it for eventual ejection into the duodenum (small intestine). And it is these waves, along with the stomach's rhythmic contractions, as well as its secretory and motor functions, that cause your stomach to gurgle after you eat.