Download Human Anatomy/Physiology

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

Classifying bacteria
(continued)

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
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Prevention and Control
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Mechanisms of transmission
 Person-to-person contact
 Can be prevented by education
 Can be prevented by using aseptic technique (table 4-6)
 Environmental contact
 Can be prevented by avoiding contact
 Can be prevented by safe sanitation practices
 Opportunistic invasion
 Can be prevented by avoiding changes in skin and mucous
membranes
 Can be prevented by cleansing of wounds.
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Prevention and control (continued)
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Transmission by a vector
 Can be prevented by reducing the population of vectors
and reducing contact with vectors
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Prevention and control (continued)
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Other prevention and treatment strategies
 Vaccination – stimulates immunity
 Chemicals – destroy or inhibit pathogens
 Antibiotics – natural compounds derived from living
organisms (see next page)
 Synthetic compounds (examples: ACT and AZT)
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Neoplasm
New matter
 An abnormal growth of
cells
 Also called a tumor
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Types of tumors
Benign – remain
localized within the
tissue where they arose
 Malignant – spreads to
other regions of the
body
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Benign tumors
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Tend to stay together
Often surrounded by
a capsule of dense
tissue
Often welldifferentiated
Usually not life
threatening unless
they interrupt a vital
function
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Causes of Cancer
Hyperplasia – process that produces too many cells
 Anaplasia – production of undifferentiated tumor
cells
 All cancers are caused by a mistake or problem in
cell division
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Factors that can play a role in cancer:
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Genetic factors
 Oncogenes – abnormal “cancer genes”
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Carcinogens – chemicals that affect genetic activity,
often causing abnormal cell reproduction
 Mutagens – cause changes in DNA structure
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Age
Environment
 Sunlight causing skin cancer; radiation; asbestos fibers
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Viruses
 HPV – human papillomavirus (cervical cancer)
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Malignant tumors
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No capsule
Don’t stay in one
place
Cells fall away and
start new tumors
somewhere else
Metastasis –
spreading of
abnormal cells
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Methods used to
detect presence of
cancer
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Self examinations
Diagnostic imaging
 Radiography (x-rays)
 Computed
Tomography (CT scans)
 Magnetic Resonance
Imaging (MRI)
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Methods of detection
(continued)
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Biopsy
 Removal of some tissue for
further tests and
examination
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Blood Tests
 Example: some forms of
cancer elevate blood
concentration levels of
calcium ions
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Absence of early detection
and/or treatment usually
results in an advanced
illness followed by death
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Many patients suffer from cachexia:
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Loss of appetite
Severe weight loss
Physical weakness
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Treatment options:
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Surgery – removal of
cancerous tissue
Chemotherapy –
Attacking malignant
cells with “cell
killing” drugs
Radiation therapy –
Use of radiation to
destroy cancerous
malignant cells
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Treatment options
(continued)
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Laser therapy –
Intense beam of light
to destroy tumors
Immunotherapy –
New treatment that
bolsters the body’s
own defenses
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A number of body
responses that
attempts to minimize
injury to body tissue.
Four primary signs:
Redness
 Heat
 Swelling
 Pain
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Inflammation
Mediator (I.M.)
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Body chemicals
released when tissues
undergo damage:
 Histamines
 Prostaglandins
 Kinins
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I.M. causes blood
vessels to dilate
 Increases blood volume
to injured area and
causes redness and heat
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I.M. allows white
blood cells to travel
quickly to injured site
Liquids leaking out of
vessels causes
swelling or edema
Fluids that
accumulate in the
inflamed tissue is
called inflammatory
exudate
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Chemotaxis
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Pus
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Movement of white
blood cells to injured
area
Inflammatory exudate
thickens with used
white blood cells
Process of inflammatory
response eventually
eliminates the irritant
and healing can begin.
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Regeneration
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Replacement
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Healing and repair of
tissue (same cells)
Different cells take
place of injured cells
and results in
scarring
Tissue repairs are a
combination of
regeneration and
replacement
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Sometimes the
inflammatory
response affects the
entire body
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Fever – elevated body
temperature
Increased body
temperature often
kills or helps fight off
pathogens.
Note: Study diagram
on page 97.