ANATOMY

Detailed explanation-1: -Pathogens present in food substances killed by antimicrobial substances present in saliva, mucus produced by epithelial lining of gastrointestinal tract, and stomach acid or hydrochloric acid. So, if a pathogen present in food got past saliva, it would be targeted by mucus and stomach acid.

Detailed explanation-2: -The first line of defence (or outside defence system) includes physical and chemical barriers that are always ready and prepared to defend the body from infection. These include your skin, tears, mucus, cilia, stomach acid, urine flow, ‘friendly’ bacteria and white blood cells called neutrophils.

Detailed explanation-3: -Stomach acid is our first line of defense against harmful bacteria and parasites in food, liquid, and air we consume. On the other end of the stomach, HCL prevents normal bacteria present in the intestines from travelling into the stomach and esophagus, where they can cause problems.

Detailed explanation-4: -Answer and Explanation: Fever is not the first line of defense; it is considered the second line of defense. Suppose the first line of defense couldn’t protect the body, and the pathogen still enters the body. In that case, the second line of defense protects the body, including fever, inflammation, and phagocytosis.