Final answer:
Stomach acid, primarily composed of hydrochloric acid, kills most pathogens ingested with food or water, contributing to the body's defense against infections. Saliva and mucus also play a role in trapping and destroying bacteria, while enzymes like lysozyme break down bacterial cell walls.
Step-by-step explanation:
The Role of Stomach Acid in Preventing Infection
The acidity of the fluids in your stomach serves as a partial defense against infection by creating an environment that is lethal to many pathogens. This acidic environment is primarily due to hydrochloric acid which is very effective at killing off pathogens that enter the stomach with food or water. Moreover, other components like saliva and mucus trap microbes and facilitate their removal, while saliva also contains lysozyme, an enzyme that can destroy bacteria by digesting their cell walls. In addition, the stomach secretion and digestive enzymes called proteases break down proteins and kill most pathogens that are ingested. While most germs are neutralized by this harsh acidic environment, certain bacteria such as Helicobacter pylori have mechanisms to survive the stomach's acidity, which can lead to infections, ulcers, or even increase the risk of stomach cancer.