chapter 4 – mechanisms of disease. health physical, mental, and social well-being—not merely...
TRANSCRIPT
HUMAN ANATOMY/PHYSIOLOGY
Chapter 4 – Mechanisms of Disease
Disease Terminology
Health Physical, mental, and social well-being—not
merely the absence of disease disease
An abnormality in body function that threatens health
Pathology Study of disease
Pathogenesis The pattern of a disease’s development
Disease Terminology
Etiology the study of the factors that cause a disease
Idiopathic Refers to a disease with an unknown cause
Symptoms The objective and subjective abnormalities
associated with a disease Syndrome
Collection of different signs and symptoms, usually with a common cause, that presents a clear picture of a pathological condition.
Disease Terminology
Acute Signs and symptoms appear suddenly, persist
for a short time, then disappear Chronic
Diseases that develop slowly and last for a long time (perhaps for life)
Incubation Latent (hidden) stage of a disease
Convalescence recovery
Remission Reversal of a chronic disease
Patterns of Disease
Epidemiology Study of occurrence, distribution, and
transmission of diseases in human populations Endemic diseases
Native to a local population Epidemic
Occurs when a disease affects many people at the same time
Pandemic Widespread, perhaps global, epidemic
Patterns of Disease
Discovering the cause of a disease is difficult because many factors affect disease transmission
Disease can be fought through prevention and therapy (treatment)
Mechanisms of Disease
Pathophysiology Study of
underlying physiological aspects of disease
Genetic Mechanisms Pathogenic
organisms Tumors and cancer Physical and
chemical agents malnutrition Autoimmunity Inflammation degeneration
Risk Factors (predisposing conditions)
Genetic factors Age Lifestyle Stress Environmental factors Preexisting conditions
Pathogenic Organisms
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
Pathogenic Organisms
Classifying Bacteria Oxygen requirements
Aerobic (needs oxygen)
Anaerobic (doesn’t need oxygen)
Staining (how cell wall accepts staining) Gram positive
(accepts stain) Gram negative (does
not accept stain Certain antibiotics work
for certain cell walls
Pathogenic Organisms
Classifying bacteria (continued) Shape
Rod-shaped (bacilli/bacillus)
Round-shaped (cocci/coccus)
Spiral shaped (spirillum/spirilla)
Pathogenic Organisms
Some bacteria produce spores (endospores) that are resistant to chemicals, heat, and dry conditions
Pathogenic Organisms
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)
Pathogenic Organisms
Fungi 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)
Pathogenic Organisms
Examples of fungal infections: Yeast cells infect
membranes all over the body
Athlete’s foot ringworm
Pathogenic Organisms
Protozoa One-celled
organisms that have a nucleus
Cause disease by being parasites
Major groups: Amoebas Flagellates Ciliates Sporozoa
Pathogenic Organisms
Pathogenic Animals Called Metazoa Cause disease by
acting like a parasite
An organism that spreads disease to other organisms is called a vector
Pathogenic Organisms
Major groups of pathogenic animals Nematodes
(roundworms) Transmit disease
through foods or biting insects
Platyhelminths (flatwroms) Tapeworm
Arthropods Ticks, mites, lice,
fleas, stinging bees, wasps, spiders
Pathogenic Organisms
Virus 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
Pathogenic Organisms
Virus (continued) Very small
200 can fit on a period on a typed page
Examples of viral diseases Polio AIDS Cold Flu Herpes rabies
Pathogenic Organisms
Prevention and Control 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.
Pathogenic Organisms
Prevention and control (continued) Transmission by a vector
Can be prevented by reducing the population of vectors and reducing contact with vectors
Pathogenic Organisms
Prevention and control (continued) 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)
Tumors and Cancer
Neoplasm New matter An abnormal growth of
cells Also called a tumor
Types of tumors Benign – remain
localized within the tissue where they arose
Malignant – spreads to other regions of the body
Tumors and Cancer
Benign tumors Tend to stay
together Often surrounded
by a capsule of dense tissue
Often well-differentiated
Usually not life threatening unless they interrupt a vital function
Tumors and Cancer
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
Tumors and Cancer
Factors that can play a role in cancer: Genetic factors
Oncogenes – abnormal “cancer genes” Carcinogens – chemicals that affect genetic
activity, often causing abnormal cell reproduction Mutagens – cause changes in DNA structure
Age Environment
Sunlight causing skin cancer; radiation; asbestos fibers
Viruses HPV – human papillomavirus (cervical cancer)
Tumors and Cancer
Malignant tumors No capsule Don’t stay in one
place Cells fall away and
start new tumors somewhere else
Metastasis – spreading of abnormal cells
Pathogenesis of Cancer
Methods used to detect presence of cancer Self examinations Diagnostic imaging
Radiography (x-rays) Computed
Tomography (CT scans)
Magnetic Resonance Imaging (MRI)
Pathogenesis of Cancer
Methods of detection (continued) Biopsy
Removal of some tissue for further tests and examination
Blood Tests Example: some forms of
cancer elevate blood concentration levels of calcium ions
Absence of early detection and/or treatment usually results in an advanced illness followed by death
Pathogenesis of Cancer
Many patients suffer from cachexia: Loss of appetite Severe weight loss Physical weakness
Pathogenesis of Cancer
Treatment options: Surgery – removal
of cancerous tissue Chemotherapy –
Attacking malignant cells with “cell killing” drugs
Radiation therapy – Use of radiation to destroy cancerous malignant cells
Pathogenesis of Cancer
Treatment options (continued) Laser therapy –
Intense beam of light to destroy tumors
Immunotherapy – New treatment that bolsters the body’s own defenses
Inflammatory Response
A number of body responses that attempts to minimize injury to body tissue.
Four primary signs: Redness Heat Swelling Pain
Inflammatory Response
Inflammation Mediator (I.M.) Body chemicals
released when tissues undergo damage: Histamines Prostaglandins Kinins
I.M. causes blood vessels to dilate Increases blood volume
to injured area and causes redness and heat
Inflammatory Response
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
Inflammatory Response
Chemotaxis Movement of white
blood cells to injured area
Pus Inflammatory exudate
thickens with used white blood cells
Process of inflammatory response eventually eliminates the irritant and healing can begin.
Inflammatory Response
Regeneration Healing and repair of
tissue (same cells) Replacement
Different cells take place of injured cells and results in scarring
Tissue repairs are a combination of regeneration and replacement
Inflammatory Response
Sometimes the inflammatory response affects the entire body Fever – elevated
body temperature Increased body
temperature often kills or helps fight off pathogens.
Note: Study diagram on page 97.