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Chapter 15 Lecture 1 (An Overview of the Body’s Defenses (Our body needs…

- - - - Correct chemical receptors not present on human cells
      - Conditions may be incompatible with those needed for pathogen’s survival
      - Or we can just say that the absence of necessary receptors and lack of suitable environment in the body gives protection or species resistance
- - - - Thin outer covering of the mucous membranes
      - Epithelial cells are living
      - Tightly packed to prevent entry of many pathogens
      - Continual shedding of cells carries away microorganisms
      - Dendritic cells below epithelium phagocytize pathogens
      - Goblet and ciliated columnar cells help remove invaders
- - - - Some punch holes in the cytoplasmic membranes of the pathogens
      - Interrupt internal signaling or enzymatic action
      - Some act as a chemomatic factors (chemicals that recruit WBC to a site)
      - Others assemble to form fibers and microscopic nets to grab the invading bacteria
  - - - Stomach acid is an example
- - - - Multiple layers of tightly packed cells
        
        Few pathogens can penetrate these layers (barrier)
        
        Deepest layer of epidermis continually divides pushing the daughter cells towards the surface this is shedding
        
        Shedding of dead skin cells removes microorganisms (clearance)
      - Epidermal dendritic cells phagocytize pathogens they devour pathogens nonspecifically and play a role in adaptive immunity
    - - Collagen fibers give skin strength and pliability to prevent many jabs and abrasions that could introduce microorganisms
      - Blood vessels in the dermis deliver defensive cells and chemicals such as antimicrobial peptides and sweat glands secrete perspiration, which has salt, antimicrobial peptides and lysozyme.
        
        What do salts do? They draw water osmotically from invading cells, stopping their growth and that kills them
- - - - Again, salt inhibits growth of pathogens
      - Antimicrobial peptides act against microorganisms
      - Sweat glands secrete a class of antimicrobial peptides called dermcidin that act on Gram – and Gram + bacteria and fungi
      - Lysozyme destroys cell wall of bacteria
    - - Helps keep skin pliable and less likely to break