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Chapter 10
Bacteria and
Viruses
Section 10C-2
Defense against infectious disease
A. Structural defense – “First line of
defense” keep pathogens out!
1. Skin and mucous membranes lining
respiratory, digestive and urinary tracts
2. Mucus traps microbes and disposes of them
3. Stomach acid kills swallowed pathogens
4. Intestinal flora (good bacteria living in
intestines) competes against bad bacteria
5. Tear glands make lysozyme, which kills
bacteria entering eyes
Section 10C-2
Defense against infectious disease
B. Nonspecific defenses - “Second line of
defense” Inflammatory response, phagocytic
cells, lymphatic system, fever
–
–
Inflammation – increases blood flow in
response to chemicals released by infected cells
Phagocytic cells – white blood cells arrive due
to increased blood flow, recognize invaders,
form a barrier
Pus: fluid, WBC and dead pathogens
Section 10C-2
Defense against infectious disease
B. Nonspecific defenses (cont.)
–
–
Lymphatic system – helps clean body of
pathogens and toxins, phagocytizes
pathogens
Fever – Raised body temperature, makes
environment less favorable for many
pathogens & accelerates reactions that
activate defenses (if fever is too high, may
cause damage to body tissues)
Section 10C-2
Defense against infectious disease
C. Specific defenses – “Third line of
defense” – immune system (Ch. 22)
– Antibodies – proteins made by specific cells
in the blood that combat specific pathogens
or their toxins
– Other special cells with particular duties
have “chemical memory” of pathogen
Section 10C-2
Defense against infectious disease
D. Medical control- “chemical warfare”
–
–
Chemotherapy – use of chemical agents to treat or
prevent disease. Meant to injure the pathogen without
harming host’s body but may have side effects.
Antibiotics: Chemicals produced by living things
Work by interfering with enzymes and metabolic pathways
that bacteria have (& humans don’t have), like cell wall
synthesis
Are nonspecific (kill many kinds of bacteria), but don’t kill virus
Types: Bactericidal- kill bacteria, Bacteriostatic- inhibit
growth of bacteria
Example: Penicillin – The first antibiotic, a mold, discovered
by Sir Alexander Flemming,
10C-3 Disorders: diseases not
caused by a pathogen
1. Inherited disorders – due to a gene or inherited
2.
3.
4.
5.
tendency (ex. diabeties)
Injuries – broken bone, burns, etc.
Deficiency disease – lack of a vitamin/mineral
Chemical poisoning or radiation sickness – due
to exposure to environmental factors
Other organic disorders like stroke, kidney
stones, etc. caused by unknown or partially
understood causes
10C-3 Disorders (cont.)
• Benign tumors – abnormal growth of cells
• Biopsy – take tissue sample
• Pathologist – tissue specialist, analyzes tissue
from biopsy to determine benign or malignant
(benign tumors usually surgically removed)
• Cancer – malignant tumor (rapid cell growth)
• May metastasize (separate from parent tumor
and spread to other parts of the body)
10C-3 Disorders (cont.)
• Cancer
1. Initiation: 1st step to developing cancer,
cells become partially cancerous, happens
in 1 of 3 ways
A. Carcinogenic chemicals – cause cancer
(ex. tobacco products)
B. Radiation – ultraviolet or x-rays can cause
(ex. skin cancer)
C. Viruses – some viruses linked to some
cancers (ex. HPV  cervical cancer)
10C-3 Disorders (cont.)
• Cancer
2. Promotion: once cell has become
potentially cancerous, diet/general
health/genetic makeup help promote
conversion of initiated cells to cancer
cells (tumor forms)
– see p. 292 for steps to reduce cancer risk
10C-3 Disorders (cont.)
• Cancer Treatments
1. Surgery – leading method, remove cancer cells
2. Radiation – x-rays or radioactive isotope
emission to destroy cancer cells, side effects
harsh, can cause new tumors
3. Chemotherapy – chemicals aimed at
destroying cancer cells, side effects harm other
cells in the body
Facet: clinical death – absence of brain waves
for 24-48 hours