The Function of the Stomach Is to Process Food into a Fluid Consistency and Release It into the Intestine at a Controlled Rate
Among animals there is tremendous diversity in the anatomy and motility patterns of the stomach. The following discussion applies best to the animals with the simplest stomachs, such as the dog and cat, but is probably also a reasonable description of the activity of the somewhat more complex stomachs of the pig, horse, and rat.
The complex motility patterns of the ruminant stomach are discussed in Chapter 31.The function of the stomach is to serve food to the small intestine. There are two important aspects of this function: rate of delivery and consistency of material. The stomach serves both as a storage vat to control the rate of delivery of food to the small intestine and as a grinder and sieve that reduces the size of food particles and releases them only when they are broken down to a consistency compatible with small- intestinal digestion.
The stomach is divided into two physiological regions, each of which has a different impact on gastric function. The proximal region, at the esophageal end of the stomach, serves a storage function, retaining food as it awaits eventual entry into the small intestine. The distal region serves a grinding and sieving function, breaking solid pieces of food down into particles small enough for small-intestinal digestion.