Summary of Innate (Nonspecific) Body Defenses

Question 1

Intact skin (epidermis) (Surface membrane barriers—first line of defense)

Answer 1

Forms mechanical barrier that prevents entry of pathogens and other harmful substances into body

Question 2

Acid mantle (Surface membrane barriers—first line of defense)

Answer 2

Skin secretions make epidermal surface acidic, which inhibits bacterial growth; sebum also contains bacteria-killing chemicals

Question 3

Keratin (Surface membrane barriers—first line of defense)

Answer 3

Provides resistance against acids, alkalis, and bacterial enzymes

Question 4

Intact mucous membranes (Surface membrane barriers—first line of defense)

Answer 4

Form mechanical barrier that prevents entry of pathogens

Question 5

Mucus (Surface membrane barriers—first line of defense)

Answer 5

Traps microorganisms in respiratory and digestive tracts

Question 6

Nasal hairs (Surface membrane barriers—first line of defense)

Answer 6

Filter and trap microorganisms and other airborne particles in nasal passages

Question 7

Cilia (Surface membrane barriers—first line of defense)

Answer 7

Propel debris-laden mucus away from lower respiratory passages

Question 8

Gastric juice (Surface membrane barriers—first line of defense)

Answer 8

Contains concentrated hydrochloric acid and protein-digesting enzymes that destroy pathogens in stomach

Question 9

Acid mantle of vagina (Surface membrane barriers—first line of defense)

Answer 9

Inhibits growth of bacteria and fungi in female reproductive tract

Question 10

Lacrimal secretion (tears); saliva (Surface membrane barriers—first line of defense)

Answer 10

Continuously lubricate and cleanse eyes (tears) and oral cavity (saliva); contain lysozyme, an enzyme that destroys microorganisms

Question 11

Phagocytes (Cellular and chemical defenses—second line of defense)

Answer 11

Engulf and destroy pathogens that breach surface membrane barriers; macrophages also contribute to immune response

Question 12

Natural killer cells (Cellular and chemical defenses—second line of defense)

Answer 12

Promote cell lysis by direct cell attack against virus-infected or cancerous body cells; do not depend on specific antigen recognition

Question 13

Inflammatory response (Cellular and chemical defenses—second line of defense)

Answer 13

Prevents spread of injurious agents to adjacent tissues, disposes of pathogens and dead tissue cells, and promotes tissue repair; releases chemical mediators that attract phagocytes (and immune cells) to the area

Question 14

Antimicrobial chemicals- Complement (Cellular and chemical defenses—second line of defense)

Answer 14

Group of plasma proteins that lyses microorganisms, enhances phagocytosis by opsonization, and intensifies inflammatory response.

Question 15

Antimicrobial chemicals- Interferons (Cellular and chemical defenses—second line of defense)

Answer 15

Proteins released by virus-infected cells that protect uninfected tissue cells from viral takeover; mobilize immune system

Question 16

Antimicrobial chemicals- Fluids with acid pH (Cellular and chemical defenses—second line of defense)

Answer 16

Normally acid p H inhibits bacterial growth; urine cleanses the lower urinary tract as it flushes from the body

Question 17

Fever (Cellular and chemical defenses—second line of defense)

Answer 17

Systemic response triggered by pyrogens; high body temperature inhibits multiplication of bacteria and enhances body repair processes