Which system uses acids and enzymes produced by the stomach to destroy invaders swallowed or consumed?

• A. Respiratory system
• B. Lymphatic system
• C. Digestive system
• D. Endocrine system

Answer: (C)

The digestive system. When you swallow, the stomach releases gastric acid (hydrochloric acid) and enzymes like pepsin. This combination creates a hostile chemical environment that helps destroy many ingested microbes and begins protein digestion, providing a first line of defense as material moves through the digestive tract. The other systems don’t use stomach acids to protect against swallowed invaders—respiratory deals with inhaled pathogens, the lymphatic system supports immune functions, and the endocrine system uses hormones.