Answer to Question #342872 in Human Anatomy and Physiology for Eleptheria

Question

How do motility and secretions of the stomach contribute to the digestive process?

Answer 1

Gastrointestinal (GI) motility refers to the movement of food from the mouth through the pharynx (throat), esophagus, stomach, small and large intestines and out of the body. The GI system is responsible for digestion.

Gastrointestinal motility refers to the contraction of the smooth muscles of the gastrointestinal tract.

Contractions of gastric smooth muscle serves two basic functions:

• ingested food is crushed, ground and mixed, liquefying it to form what is called chyme.
• chyme is forced through the pyloric canal into the small intestine, a process called gastric emptying.

Gastric secretion is stimulated by the act of eating (cephalic phase) and the arrival of food in the stomach (gastric phase). Arrival of the food in the intestine also controls gastric secretion (intestinal phase). The secreted fluid contains mucus (coats and lubricates the gastric surface, and serves an important role in protecting the epithelium from acid and other chemical insults); hydrochloric acid is secreted from parietal cells into the lumen where it establishes an extremely acidic environment, it is important for activation of pepsinogen and inactivation of ingested microorganisms such as bacteria; proteases: Pepsinogen, an inactive zymogen, is activated by stomach acid into the active protease pepsin, which is largely responsible for the stomach's ability to initiate digestion of proteins; hormones: the principal hormone secreted from the gastric epithelium is gastrin, a peptide that is important in control of acid secretion and gastric motility.

So, gastric juice renders food particles soluble, initiates digestion (particularly of proteins), and converts the gastric contents to a semiliquid mass called chyme together with GI motility thanks to which ingested food is crushed, ground and mixed , thus preparing it for further digestion in the small intestine.