Nonspecific Defenses of the Host

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Nonspecific Defenses of the Host Powered By Docstoc
					Nonspecific Defenses
    of the Host
                     The Immune System
Innate (Nonspecific) Immunity                          Acquired
                                                       (Specific)
                                                       Immunity
First line of defense            Second line defense   Third line of
(barriers at the body surface)                         defense
•Skin                            •Inflammation      •T cell lymphocytes
•Mucous membranes                •Phagocytes        •B cell lymphocytes
•Secretions                      •Fever             •Antibodies
•Reflexes                        •Complement system
•Normal microbiota               •Interferon
The First Line of Defense

      Surface Barriers
               Epidermis (Skin)
• Intact surface is rarely
  penetrated by microbes
• Stratum Corneum is made
  of dead keratinized cells
  that form an armor plating
• Dead karatinized cells are
  constantly sloughing off
               Epidermis
• Dry: Most areas of the skin are too dry for
  microbial growth.
• Acidic: (pH 5): The sebaceous glands produces
  sebum, an unsaturated fatty acid.
• Temperature: slightly cooler than 37 degrees
• Resident microflora: The natural flora out
  competes pathogenic organisms.
              Mucous Membranes
• Mucous membranes are surfaces areas
  lining the Respiratory, G.I., and
  urogenital tracts.
• These membranes are considered to be
  outside the body.
• Mucous membranes are involved in
  either secretion or absorption and thus
  cannot be covered with an armor of
  dead cells.
• Membranes must be bathed in fluids
  (warm, wet environments that would
  readily colonize bacteria if they were
  not protected by a number of
  defenders.
   Defense of the Mucous Membrane
• Goblet cells produce mucus, a thick
  sticky substance composed of
  polysaccharide and protein.
• Mucus contains carbohydrate
  structures similar to the ones on
  mucosal cells surfaces
• Mucus traps bacteria before they can
  reach membrane.
• Muco-ciliary escalator pushes
  microbes and debris outside the
  respiratory system
• M-cells funnel bacteria into waiting
  phagocyts
         Eyes (lacrimal apparatus
• Washing action of
  tears along with the
  blinking action of the
  eyelid mechanically
  removes bacteria and
  debris
• Lysozyme attacks
  peptidoglycan layer of
  bacteria
                Stomach
• Low pH and digestive enzymes kill
  microbes and endospores that enter the GI
  tract.
                  Reflexes
• Types: Coughing
  sneezing, blinking,
  vomiting
• Function: Expel
  microbes and toxins
Earwax

         Antibacterial and
          insect repellent

				
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posted:9/15/2011
language:English
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