CHAPTER 16 Nonspecific defense mechanisms

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CHAPTER 16Nonspecific defense mechanisms
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Chemical factors

• Sebaceous glands --gt sebum (acidic)
• Sweat glands --gt per- spiration w/ lysozyme
• Stomach glands --gt gastric juice
• Vaginal secretions - acidic
• Blood - transferins

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Skin and Mucous membranesmechanical factors

• Intact skin (dermis and epidermis, keratin)
• Mucous membranes - GI, respiratory and
  genitourinary tracts
• Lacrimal apparatus
• Saliva
• Mucous and cilia
• Urine
• Vaginal secretion

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Formed elements in blood - leukocytes

• White blood cells Staining makes the granules
  apparent. The monocyte enlarges to become a
  macrophage. The lymphycyte has a large nucleus
  it is not a phagocyte but either secretes
  antibody of kills infected cells

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Components of lymphatic system

• Interstitial fluid picked up by lymph vessels
  becomes lymph. Macrophages in lymph nodes remove
  microbes. Lymph enters general blood circulation
  at right lymphatic duct

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Mechanism of phagocytosis

• 4 stages
• chemotaxis - chem.attract
• adherence to phagocytes plasma membrane
• ingestion as pseudopods surround microbe --gt
  phagosome
• digestion - phagosome fuses with lysosome.
  Enzymes digest fragments discharged

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Inflammation

• 4 signs redness, pain heat and swelling
• 3 functions destroy agent, or wall it off,
  repair or replace tissue
• Vasodilation (histamine, kinins,
  prostaglandins_--gt edema
• Blood clot, abcess with pus

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Phagocyte migration phagocytosis

• Phagocytes migrate and marginate and emigrate
• 1st are neutrophylls
• 2nd are macrophages
• pus is dispersed or absorbed
• Tissue repair depends on type of tissue stroma
  parenchyma

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Fever

• System response to microbe and/or toxins
• Gram neg. organisms cause phagocytes to release
  interleukin-1 hypothalmus releases
  prostaglandins --gt reset thermostat higher
• Blood vessel constriction --gt shivering until
  higher temperature is reached.
• Infection subsides b.v.dilation - skin warm,
  sweating --gt crisis
• Higher temp. inhibits microbial growth

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Antimicrobial substancescomplement system

• Serum proteins lyse foreign cells, part of
  inflammation and phagocytosis
• Activation - classical pathway - reaction of
  antibodies to antigens
• alternative pathway - interaction of proteins and
  polysaccharides

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Cytolysis - complement cascade
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Microbes are punctured - contents leak out
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Inflammation

• C3a and C5a bind to mast cells, basophils and
  platelets trigger release of histamine
• --gt in blood vessel permeability
• C5a attracts phagocyte to site of complement
  activation

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Results of complement

• Complement components used in complement fixation
• Inflammation, opsonization (easier for phagocyte
  to adhere to microbes), complement inactivation
• complement can --gt collagen vascular disorders
  --gt hypersensitivity (anaphylaxis)
• C3 deficiency - increased susceptibility

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Antiviral action of alpha and beta interferon