2. Non-Specific Defense (pg 6)
• Non-specific defenses are directed against all
pathogens, regardless of their nature
3. 1st Line of Defense
Physical Barriers:
1. Skin: Cells are tightly packed and contain the
tough protein keratin, which makes it difficult
for pathogens to penetrate.
4. 1st Line of Defense
Physical Barriers:
1. Skin: Cells are tightly packed and contain the
tough protein keratin, which makes it difficult
for pathogens to penetrate.
2. Mucous membranes: Line respiratory and
digestive tracts.
5. 1st Line of Defense
Physical Barriers:
1. Skin: Cells are tightly packed and contain the
tough protein keratin, which makes it difficult
for pathogens to penetrate.
2. Mucous membranes: Line respiratory and
digestive tracts.
3. Fluids: Tears, saliva, urine: flush pathogens
out of the body
6. 1st Line of Defense
Protective Secretions:
1. Skin secretions are acidic and sebum contains
chemicals that inhibit bacterial growth
7. 1st Line of Defense
Protective Secretions:
1. Skin secretions are acidic and sebum contains
chemicals that inhibit bacterial growth
2. Stomach produces hydrochloric acid, which
kills pathogens
8. 1st Line of Defense
Protective Secretions:
1. Skin secretions are acidic and sebum contains
chemicals that inhibit bacterial growth
2. Stomach produces hydrochloric acid, which
kills pathogens
3. Saliva and tears contain lysozyme, an enzyme
that destroys bacteria
9. 1st Line of Defense
Protective Secretions:
1. Skin secretions are acidic and sebum contains
chemicals that inhibit bacterial growth
2. Stomach produces hydrochloric acid, which
kills pathogens
3. Saliva and tears contain lysozyme, an enzyme
that destroys bacteria
4. Mucus traps microorganisms
10. 2nd Line of Defense
Chemical Action
1. Complement: group of proteins that are
activated by contact with foreign substances.
Activated complement proteins enhance
phagocytosis and inflammation and cause
bacterial cells to rupture
11. 2nd Line of Defense
Chemical Action
1. Complement: group of proteins that are
activated by contact with foreign substances.
Activated complement proteins enhance
phagocytosis and inflammation and cause
bacterial cells to rupture
2. Interferon: Produced by virus-infected cells.
Stimulates neighboring cells to block their
virus receptors so they don’t get infected
12. 2nd Line of Defense
Phagocytes
1. Neutrophils: First to arrive at site of infection.
Engulf a few bacteria and then die. “Suicide
mission”. Pus = dead neutrophils
13. 2nd Line of Defense
Phagocytes
1. Neutrophils: First to arrive at site of infection.
Engulf a few bacteria and then die. “Suicide
mission”. Pus = dead neutrophils
2. Macrophages: Large cells. Arrive later and
clean up dead neutrophils and any remaining
bacteria. “Clean up crew”
14. 2nd Line of Defense
Phagocytes
1. Neutrophils: First to arrive at site of infection.
Engulf a few bacteria and then die. “Suicide
mission”. Pus = dead neutrophils
2. Macrophages: Large cells. Arrive later and
clean up dead neutrophils and any remaining
bacteria. “Clean up crew”
3. Natural Killer Cells: Type of lymphocyte that
kills cancer cells and virus-infected cells.
15. 2nd Line of Defense
Fever
1. Macrophages release pyrogens, which cause
the hypothalamus to increase body
temperature
16. 2nd Line of Defense
Fever
1. Macrophages release pyrogens, which cause
the hypothalamus to increase body
temperature
2. High fevers are dangerous, but mild fevers
are beneficial because they decrease
availability of iron and zinc (which slows
bacterial growth) and increase metabolic rate
(which allows body cells to heal faster).
17. 2nd Line of Defense
Inflammation
1. Occurs in response to tissue damage
18. 2nd Line of Defense
Inflammation
1. Occurs in response to tissue damage
2. Signs = redness, heat, swelling, and pain
19. 2nd Line of Defense
Inflammation
1. Occurs in response to tissue damage
2. Signs = redness, heat, swelling, and pain
3. Increases blood flow to the damaged area,
which brings white blood cells and clotting
proteins.
20. 2nd Line of Defense
Inflammation
1. Occurs in response to tissue damage
2. Signs = redness, heat, swelling, and pain
3. Increases blood flow to the damaged area,
which brings white blood cells and clotting
proteins.
4. Inflammation is only helpful when it is
temporary and localized. Chronic or systemic
inflammation is damaging and dangerous.
Symptoms: High white blood cell count,
fever, decreased blood pressure (caused by
vasodilation)
