Chapter 4 Inflammation and Infection

Types of defense mechanisms

• Physical or surface barriers (nonspecific)

• Inflammation (nonspecific)

• Immune response (specific)

Inflammation

• NONSPECIFIC CELLULAR AND VASCULAR REACTION TO TISSUE

• REQUIRES BLOOD SUPPLY

• DESIGNED TO BE BENEFICIAL, PROTECTIVe

• CAN BECOME TOO INTENSE AND HARMFUL

• CLEANS UP DEBRIS TO PROMOTE HEALING

• REPELS AND DESTROYS INVADER

Trauma

triggers mast cells → histamine release

Histamine release can cause _____.

hyperemia, vascular permeability –> exudate

Hyperemia

redness, heat, increased leukocytes

Exudate

swelling/ edema

Edema can cause ______.

pain and loss of function

Changes in vascular permeability can lead to _____.

 neutrophil diapedesis (neutrophils exit the bloodstream to reach sites of infection or injury by squeezing through blood vessel walls)

Chemotaxis

signals that notify neutrophils to move to sites of infection

Phagocytosis (cell eating) can create ______.

pus

Role of Monocyte (macrophage)

killer / cleans everything up

Lymphocyte

3^rd line of defense If needed

Types of inflammation

acute and chronic

Acute inflammation

lasts less than 10 days

Chronic inflammation

lasts 2 weeks or longer

Inflammatory exudates

Appearance and amount of exudate (blood fluid) reveal acute or chronic condition

• types = serous, fibrinous, purulent, abscess, and empyema

Serous exudate

• Clear, serum-like fluid

• Acute state of inflammation

• E.g., skin blisters, cold sores

Fibrinous exudate

• Indicates larger injury with severe inflammation

• E.g., strep throat, bacterial pneumonia forming mesh-like lesion

• Superficial skin – scab

Purulent exudate

pus

Abscess

collection of pus

Empyema

accumulation of pus in body cavity

Inflammatory lesions

• Due to physical or pathologic injury

• include:

  • Abscesses (pimples)

  • Ulcers

  • Cellulitis

Tissue repair is an ______.

Ongoing process – can be slowed by disease, malnutrition, compromised immune system

Regeneration

Leads to normal function

Fibrous connective tissue repair/scar formation

does not lead to normal function

Tissue healing types

1. primary union

2. secondary union

• healing time dependent on wound size

Primary union (first intent)

• Involves approximating edges of wound

• Steps of primary healing:

  • Forms scab

  • After 1 to 2 days, new capillaries begin to bridge gap between wound edges

  • Fibroblast grows across deeper wound layers forming granulation tissue

  • Scar forms

Secondary union (2nd intent)

• Involves larger, deeper wounds with more inflammation than primary union

• Needs more capillaries, fibroblasts, and collagen

• Steps of secondary healing:

  • After 1-week, new soft red tissue produced

    • Granulation tissue

  • Scar tissue formed

Impediment to healing

• Amount of dead tissue or debris

  • Dirt, bacteria, dead leukocytes, other contaminants

Factors affecting healing time

• Age

• Size of wound

• Location

• Nutrition (Protein, Vit C)

• Immobility

• Circulation

• Organism virulence

• Steroids

Debridement

• Speeds healing

• Process of washing or cutting away necrotic tissue and foreign material

Complications of wound healing

• Poor or excessive scar formation

  • May lead to wound dehiscence

    • Separation of tissue margins

  • May result in a keloid scar

    • Excessive collagen formation

  • May result in adhesions

    • Fibrous bands of tissue that attach to surfaces of adjacent organs as scar tissue develops

Infection

Invasion of microorganisms causing cell or tissue injury

• can be caused by normal flora, opportunistic, and pathogenic microorganisms

Pathogenic

• Microorganisms causing disease

Opportunistic

• Normal flora become pathogenic under certain conditions

Conditions for microorganisms to become pathogenic:

• Microorganisms gain access to body through portal of entry

• Pathogen resistant to defenses of host

• High number of invading microorganisms

• Vulnerable condition of individual or host

Infectious diseases

• Leading cause of death worldwide

• Crucial to identify and track

  • Centers for Disease Control and Prevention (C D C) provide these services in the United States

• Respiratory infections are the most common
  

Staphylococcus

• Bacterium on skin

Streptococcus

• Bacterium that live on skin and in throat

Common enteric bacteria

Escherichia coli (E. coli), Klebsiella, Pseudomonas, Shigella, and Salmonella

Bacteria can be a ______.

primary or secondary disease

Virus

• Smallest infective organism

  • Must be visualized by electron microscope

• Cannot reproduce or live outside cell

• Not easily treated or killed by antibiotics

  • But antibiotics help prevent secondary infections

• Immunizations effective in preventing

  • E.g., measles, mumps, rubella, smallpox

• Latent viruses lay dormant in cells and replicate

  • Causing symptoms during times of stress

Fungi

• Microscopic plant-like organisms larger than bacteria

• Only a few are pathogenic

• Types of infections:

  • Tinea - Skin

    • Ringworm, athlete’s foot

  • Candida- yeast infection

    • Superficial infection of skin and mucous membranes

• Treated with antibiotics and antifungal medications

• Often difficult to cure and may require long-term therapy

Rickettsiae

• Microscopic organisms that are intermediate between bacteria and viruses

• Must live in host cell

  • Like virus

• Spread by fleas, ticks, mites, and lice

• Rocky Mountain spotted fever

  • Most common

Protozoa

Single-celled microscopic organisms

Found in soil

• Live on dead or decaying material

Infection through bite of infected insect or ingestion of spores

Malaria- most common

Giardiasis- from infected water/food

Helminths

• Roundworms or flatworms

• Pinworms and tapeworms

  • Most common

  • Pinworms cause anal itching

  • Tapeworms cause intestinal disease due to inadequately cooked meat

Symptoms of infection

• tachycardia

• fever

• malaise (fatigue, being unwell)

• leukocytosis

• septicemia

Testing for infection

• blood

• culture and sensitivity

• antigen-antibody

• skin