finals- lymphatic

• Pathogenesis


  The origin and development of a disease
• Host defense mechanism


  The way the body protects itself from pathogens
• Host defense mechanisms


  • Nonspecific
  • Specific (adaptive immunity)
• Immune response


  The very specific 3rd line of defense
• Antibodies


  Special proteins produced in response to foreign substances called antigens
• Nonspecific host defense mechanisms


  • Generally and serve to protect the body against many harmful substances
  • Example: innate or inborn resistance
• Nonspecific host defense mechanisms


  • Mechanical and physical barriers to invasion
  • Chemical factors
  • Microbial antagonism
  • Fever
  • Inflammatory response
  • Phagocytic white blood cells
• First line of defense


  • Skin and mucus membrane as physical barriers
  • Cellular and chemical factors
• Microbial antagonism


  When indigenous microflora (resident microorganisms/bacteria) prevent colonization of "new arrivals" as a result of competition for sites and nutrients and production of lethal substances
• Second line of defense

  • Transferrin
  • Fever
  • Interferons
  • Complement system
  • Cytokines
  • Inflammation
• Transferrin


  Glycoprotein that increases in response to systemic bacterial infections; binds to iron, depriving pathogens of vital nutrient
• Fever


  Stimulated by pyrogenic (fever producing) substances like Interleukin 1 (IL-1) which augments host defenses
• Fever

  1. IL-1 secreted by phagocytes travels to hypothalamus

  2. Hypothalamus secretes prostaglandins which resets hypothalamic thermostat

  3. Nerve impulses cause shivering, higher metabolic rate, inhibition of sweating, and vasoconstriction

  4. These increase body temperature to the point set by the hypothalamic thermostat
• Interferons


  Small antiviral proteins produced by virus infected cells; they prevent viruses from multiplying
• Types of interferons

  • Alpha
  • Beta
  • Gamma
• Complement system


  A group of approximately 30 different proteins found in normal blood plasma that interact in a stepwise manner known as the complement cascade to assist in the destruction of many different pathogens
• Opsonization


  A process by which phagocytosis is facilitated by the deposition of opsonins (e.g: antibodies or certain complement fragments) onto objects (pathogens)
• Cytokines


  Chemical mediators released from many different types of cells in the body that enable cells to communicate with each other
• Inflammation


  The body's response to any local injury, irritation, microbial invasion, or bacterial toxin by a complex series of events
• Formation of inflammation

  1. Tissue injury

  2. Vasodilation

  3. Increased permeability

  4. Emigration of leukocytes

  5. Chemotaxis

  6. Phagocytosis
• Purpose of inflammation


  • Localize infection
  • Prevent the spread of microbial invaders
  • Neutralize any toxins being produced at the site
  • Aid in the repair of damaged tissue
• Major signs and symptoms of inflammation


  • Redness
  • Heat
  • Swelling or edema
  • Pain
• Inflammatory exudate


  The accumulation of fluid, cells, and cellular debris at the inflammation site
• Purulent exudate or pus

  A thick, greenish-yellow exudate containing many live and dead leukocytes
• Phagocytosis


  The process by which phagocytic white blood cells (phagocytes) surround and engulf (ingest) foreign material
• Major categories of leukocytes (white cells)

  • Monocytes
  • Lymphocytes
  • Granulocytes
• Types of granulocytes


  • Eosinophils
  • Basophils
  • Neutrophils
• Phagocytes


  The most important groups are macrophages and neutrophils
• Phagocytosis


  1. Chemotaxis

  2. Attachment

  3. Ingestion

  4. Digestion
• Opsonization


  The process by which phagocytes can attach to and ingest pathogens that have been marked with opsonins (antibodies or complement fragments)
• Ingestion phase of phagocytosis

  1. Attachment

  2. Pseudopodia extend around bacterial cell

  3. Pseudopodia fuse

  4. Bacterial cell is within the phagocyte
• Digestion phase of phagocytosis

  1. Lysosome with digestive enzymes moves toward phagosome

  2. Lysosome membrane fuses with phagosome membrane

  3. Lysosome and phagosome become a single membrane-bound vesicle

  4. Bacterial cell is digested within the phagolysosome
• Mechanisms by which pathogens escape destruction by phagocytes

  • Capsules
  • Exoenzymes that kill phagocytes
  • Not destroyed within the phagolysosome
• Additional factors that can impair host defense mechanisms

  • Nutritional status
  • Increased iron levels
  • Stress
  • Cancer and cancer chemotherapy
  • Genetic defects
  • Age
  • AIDS
  • Drugs (e.g. steroids & alcohol)
• Immunology


  The scientific study of the immune system and immune responses
• Primary functions of the immune system

  • Differentiate between self and non-self
  • Destroy that which is "non-self" (infectious agents-bacteria, viruses, parasites, fungi)
• Lines of lymphocytes derived from lymphoid stem cells

  • B lymphocytes or B cells
  • T lymphocytes or T cells
  • Natural Killer lymphocytes or NK cells
• Categories of T cells

  • Helper T cells
  • Cytotoxic T cells
• Major arms of the immune system

  • Humoral immunity (antibody-mediated)
  • Cell-mediated immunity
• Humoral immunity


  Involves the production of antibodies by B cells to destroy specific microbes