Chapter 4 – Mechanisms of Disease
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Health
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disease
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An abnormality in body function that threatens
health
Pathology
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Physical, mental, and social well-being—not merely
the absence of disease
Study of disease
Pathogenesis
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The pattern of a disease’s development
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Etiology
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Idiopathic
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Refers to a disease with an unknown cause
Symptoms
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the study of the factors that cause a disease
The objective and subjective abnormalities associated
with a disease
Syndrome
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Collection of different signs and symptoms, usually
with a common cause, that presents a clear picture of
a pathological condition.
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Acute
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Chronic
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Latent (hidden) stage of a disease
Convalescence
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Diseases that develop slowly and last for a long time
(perhaps for life)
Incubation
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Signs and symptoms appear suddenly, persist for a
short time, then disappear
recovery
Remission
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Reversal of a chronic disease
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Epidemiology
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Endemic diseases
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Native to a local population
Epidemic
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Study of occurrence, distribution, and transmission
of diseases in human populations
Occurs when a disease affects many people at the
same time
Pandemic
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Widespread, perhaps global, epidemic
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Discovering the cause of a disease is difficult
because many factors affect disease
transmission
Disease can be fought through prevention and
therapy (treatment)
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Pathophysiology

Study of underlying
physiological aspects
of disease
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Genetic Mechanisms
Pathogenic organisms
Tumors and cancer
Physical and chemical
agents
malnutrition
Autoimmunity
Inflammation
degeneration
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Genetic factors
Age
Lifestyle
Stress
Environmental factors
Preexisting conditions
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Bacteria
Tiny cells without a nucleus (prokaryotic)
 Secretes poisons (toxins) that damage normal cells
and tissues
 Form colonies in the body that disrupt normal body
functions
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Classifying Bacteria
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Oxygen requirements
 Aerobic (needs oxygen)
 Anaerobic (doesn’t
need oxygen)
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Staining (how cell
wall accepts staining)
 Gram positive (accepts
stain)
 Gram negative (does
not accept stain
 Certain antibiotics work
for certain cell walls
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Classifying bacteria
(continued)
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Shape
 Rod-shaped
(bacilli/bacillus)
 Round-shaped
(cocci/coccus)
 Spiral shaped
(spirillum/spirilla)
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Some bacteria
produce spores
(endospores) that are
resistant to chemicals,
heat, and dry
conditions
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Some bacteria have an
ability to change
genetically and make
themselves resistant
to certain antibiotics.
This can make
treatment difficult.
MRSA (methicillin
resistant
Staphylococcus aureus)
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Fungi
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Simple organisms
similar to plants but
without chlorophyll
Parasitize tissue on or
near skin or mucus
membranes
Can be single-celled
(yeasts) or
multicelled (molds)
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Examples of fungal
infections:
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Yeast cells infect
membranes all over
the body
Athlete’s foot
ringworm
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Protozoa
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One-celled organisms
that have a nucleus
Cause disease by
being parasites
Major groups:
 Amoebas
 Flagellates
 Ciliates
 Sporozoa
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Pathogenic Animals
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Called Metazoa
Cause disease by
acting like a parasite
An organism that
spreads disease to
other organisms is
called a vector
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Major groups of
pathogenic animals
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Nematodes
(roundworms)
 Transmit disease
through foods or biting
insects
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Platyhelminths
(flatwroms)
 Tapeworm
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Arthropods
 Ticks, mites, lice, fleas,
stinging bees, wasps,
spiders
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Virus
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Intracellular parasites
made of genetic
material (DNA or RNA)
Living or nonliving?
Invade cells and inject
genetic material
Some symptoms show
up immediately and
some don’t for many
years
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Virus (continued)
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Very small
 200 can fit on a period
on a typed page
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Examples of viral
diseases
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Polio
AIDS
Cold
Flu
Herpes
rabies