(a) A person inhales dust and pathogens but does not always fall sick. Explain how the body protects against such infections. (b) Name and describe…

Due to immune response shown by the body / due to ability of the body to fight

against foreign agents (pathogens)

$\displaystyle \star$ Physical barrier, Skin on our body prevents entry of pathogens / Mucus coating (of respiratory, gastrointestinal, urinogenital tract) help in trapping microbes entering our body.

$\displaystyle \star$ Physiological barrier, Acid from stomach / saliva in the mouth / tears from eyes – all prevent microbial growth.

$\displaystyle \star$ Cellular barrier, Neutrophils and monocytes in the blood as well as macrophages in tissues can phagocytose and destroy microbes.

$\displaystyle \star$ Cytokine barrier, Virus infected cell secrete proteins interferons that protect non-infected cells from further viral infection