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1st and 2nd Lines of Defense

skin - 1st line of defense  

  • 15% of an adult’s total weight
  • oil/sweat glands >> low pH on surface >> many microorganisms killed
  • prevents water loss
  • lyxozyme - enzyme in sweat that digests bacterial cell walls
  • stratum corneum - outer skin layer
    • cells constantly injured, worn, replaced
  • stratum basale - innermost skin layer, produces new skin cells
  • stratum spinosum - broad layer in middle of epidermis
  • dermis - skin layer below epidermis, gives structural support
  • mainly adipose (fat) cells below dermis
  • other surfaces leading to outside - digestive tract, respiratory tract, urogenital tract
    • mucus traps microorganisms in bronchi, cilia sweeps mucus towards glottis to stomach

cellular counterattack - 2nd line of defense 

  • uses nonspecific cellular/chemical devices to defend
  • goes after any infection w/ leukocytes
  • identity of pathogen doesn’t matter
  • lymphatic system = central location for distribution of immune system cells
  • macrophages - “big eaters”
    • ingests microbes through phagocytosis
    • uses oxygen-free radicals to destroy microbes
  • neutrophils - most abundant leukocyte
    • can release chemicals (similar to bleach) to kill all cells in surroundings
  • natural killer cells - destroys cells already infected by the microbe
    • drills hole into plasma membrane

complement system - in vertebrates, contains 20 proteins 

  • proteins encounter bacterial/fungal cell wall >> forms membrane attack complex
  • forms pore on membrane >> cell swells/bursts
  • adds on to the effects of other body defenses
  • interferons - messenger to warn other cells of the infection
    • alpha, beta, gamma
  • prostaglandin - produces clotting to block spread of pathogens

inflammatory response - localized, nonspecific response to infection 

  • infected cells release alarm signals >> blood vessels dilate >> increase blood flow >> area = red/warm
  • neutrophils, then macrophages arrive to kill microbes
    • pus = mixture of dead pathogens, tissue, neutrophils
  • temperature response - macrophages release interleukin-1 >> hypothalamus raises body temperature
    • fever >> stimulates phagocytosis, iron production
    • very high fever could start to denature enzymes
Subject: 
Biology
Subject X2: 
Biology

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