defense mechanisms three lines of defense protect the body against foreign invasion: physical or...
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Defense Mechanisms
Three lines of defense protect the body against foreign invasion:Physical or surface barriersInflammationImmune response
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Inflammation
Non-specific cellular and vascular reaction to tissue
Repels and destroys invader; cleans up debris to promote healing
Requires blood supply
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Inflammatory Process
Signs and symptoms:RednessHeatEdemaPain
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Chronic Inflammation
Last two weeks or longer Acute inflammation lasts less than 10
days
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Inflammatory Exudates
Appearance and amount of exudate (blood fluid) reveals acute or chronic condition
Serous exudate is clear serum-like fluidAcute state of inflammationSkin blisters and cold sores
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Inflammatory Exudates
Fibrinous exudate Indicates larger injury with severe
inflammationCommonly called scabStrep throat or bacterial pneumonia forming
a mesh-like lesion
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Inflammatory Exudates
Purulent exudate called “pus” Collection of pus is an abscess Accumulation of pus in body cavity is
empyema
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Inflammatory Lesions
Due to physical or pathologic injury Inflammatory lesions include:
AbscessesUlcersCellulitis
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Tissue Repair and Healing
Ongoing process Tissue repair:
Regeneration Fibrous connective tissue repairScar formation
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Tissue Repair and Healing Regeneration leads to normal function Fibrous connective tissue repair does
not
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Tissue Healing
Primary Union (First Intention)Involves approximating edges of woundSteps of primary healing:
○ Forms scab○ 1 to 2 days, new capillaries begin to bridge
gap between wound edges
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Tissue Healing
Primary Union (First Intention)Steps of primary healing:
○ Fibroblast grows across deeper wound layers forming granulation tissue
○ Scar forms○ Example of primary healing is surgical incision
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Tissue Healing
Secondary Union (Secondary Intention) Larger, deeper wounds with more
inflammation than primary unionNeed more capillaries, fibroblasts, and
collagen
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Tissue Healing
Secondary Union (Secondary Intention) After a week, new soft red tissue called
granulation tissue is producedScar tissue is formedHealing time is dependent on size of wound
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Delayed Wound Healing
Debridement (washing or cutting away necrotic tissue and foreign material) may be necessary
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Delayed Wound Healing
Factors affecting healing time:AgeSize of woundLocationNutrition
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Delayed Wound Healing
Factors affecting healing time:CirculationOrganism virulenceSteroids
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Complications of Wound Healing Poor or excessive scar formation Dehiscence - separation of tissue
margins Keloid - hard, raised scar Adhesions - fibrous bands of tissue that
attach to surfaces of adjacent organs as scar tissue develops
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Infection
Invasion of microorganisms causing cell or tissue injury
Pathogenic - microorganisms causing disease
Opportunistic - normal flora become pathogenic under certain conditions
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Infection
Conditions for flora to become pathogenicMicroorganisms gain access to body
through portal of entryPathogen is resistant to defenses of hostNumber of invading microorganisms Condition of individual or host
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Frequency and Type of Infection
Infectious diseases leading cause of death in the world
Identifying and tracking infectious diseases is crucial
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Frequency and Type of Infection
CDC - Centers for Disease Control and Prevention provide these services in the United States
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Frequency and Types of Infection
BacteriaPrimary or secondary diseaseStaphylococcus is bacterium on skinStreptococcus live on skin and in throatEscherichia coli, Kelbsiella, Pseudomonas,
Shigella, and Salmonella are common enteric bacteria
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Frequency and Types of Infection Viruses
Smallest infective organismMust be visualized by electron microscopeCannot reproduce or live outside cellViral infections are not easily treated Antibiotics do not kill a virus but help prevent
secondary infections
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Frequency and Types of Infections
VirusesImmunizations are effective in preventing
many viral diseases such as measles, mumps, rubella, and smallpox
Latent viruses lay dormant in cells and replicate and cause symptoms during times of stress
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Frequency and Types of Infection
FungiMicroscopic plant-like organisms larger than
bacteria Only few are pathogenicTypes of infections:
○ Tinea - skin○ Candida - superficial infection of skin and
mucous membranes
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Frequency and Types of Infections
FungiTreated with antibiotics and antifungal
medicationsOften difficult to cureMay require long-term therapy
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Frequency and Types of Infections
RickettsiaeMicroscopic organisms that are intermediate
between bacteria and virusesMust live in host cell like a virusSpread by fleas, ticks, mites, and liceMost common infection: Rocky Mountain
Spotted Fever
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Frequency and Types of Infections
ProtozoaSingle-celled microscopic organismsFound in soil; live on dead or decaying
materialInfection through bite of infected insect or
ingestion of sporesMalaria is most common disease
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Frequency and Types of Infections
HelminthsRoundworms or flatwormsPinworms and tapeworms are most
commonPinworms cause anal itchingTapeworms cause intestinal disease due to
inadequately cooked meat
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