defense system

• our bodies have THREE lines of defense

  1. mechanical barrier
  2. chemical barrier
  3. WHITE blood cells
• what are the two parts in the mechanical barrier?

  1. skin : stops pathogens getting into the body
  2. nostril hair : filters out pathogen that are breathed in, prevent pathogens from environment to enter body
• what are the three parts in the chemical barrier (kills pathogen already in the body)?

  1. stomach acid : destroy pathogen that taken in with food
  2. mucus in nostril, trachea, bronchi : traps pathogen
  3. ciliated cells: sweep mucus (pathogens) out
• how do the WHITE blood cells act as a barrier?

  1. phagocytes carries out phagocytosis
  2. lymphocytes produce antibody & memory cell
• ANTIBODY:

  • a protein (CHN)
  • produced by lymphocytes in response to an antigen
  • specific antibody (complementary shape) BINDS to specific antigen's binding site on the pathogen
  • marks the pathogen
• process of the slow phagocytosis

  1. phagocytes engulf the pathogen by using PSEUDOPODIUM
  2. the pseudopodium (fake intrusion) fuse with each other (close up the phagocyte and pathogen tgt)
  3. forms phagocytotic vacuole
  4. digestive enzyme is secreted into phagocytotic vacuole directly
  5. digestive enzyme digests the pathogen
• what is the process of killing a pathogen (relation between lymphocyte & phagocyte)?

  
• how the antibody produced by lymphocytes work in the defense system?

  1. the antibody binds to the pathogen antigen's active site
  2. and clump the pathogens together
  3. to then stimulates phagocytosis to happen
• state the differences between passive and active immunity:

  • passive immunity is fast
  • active immunity involves the production of memory cell and antibodies
  • passive immunity obtains antibodies from external sources i.e. serum, mother's milk