human defence system

• The Body's DEFENCE SYSTEM is to prevent pathogens from entering the body and infecting a person:

  A) nose

  B) trachea

  C) skin

  D) bronchus

  E) stomach

  
• The SKIN:

  • Provides a protective BARRIER against pathogens.
  • Produces oils / ANTIMICROBIAL SUBSTANCES to kill pathogens.
• The NOSE:

  • HAIRS and MUCUS in the nose serve as physical traps for dust, microbes, and other particles.
  • Helps prevent the entry of pathogens into the respiratory system.
• The TRACHEA and BRONCHI (Air Passages)


  • Secrete MUCUS to capture and trap pathogens.
  • Lined with CILIA, tiny hair-like structures that move mucus loaded with trapped pathogens OUT OF the respiratory system to the back of the throat.
  • From there it is swallowed and goes into the STOMACH.

  
• The STOMACH:

  • Produces HYDROCHLORIC ACID, a strong acid that destroys pathogens ingested through food or drink.
• • If the body defences fail and the pathogens enters the blood stream of a person, they are said to be INFECTED.
  • From this stage the IMMUNE SYSTEM kicks in to try and kill the pathogens.
• The IMMUNE SYSTEM / Specific defence:

  To locate and destroy pathogens that enter the body

  mainly made up of WHITE BLOOD CELLS which can fight pathogens in THREE different ways:

  • phagocytosis
  • ANTIBODY PRODUCTION
  • ANTITOXIN PRODUCTION:
• PHAGOCYTOSIS:


  A process where phagocytes:

  • tracks down a pathogen and then binds to it then engulf invading pathogens to digest it.
  • The phagocyte's membrane SURROUNDs the pathogen and engulf it.
  • enzymes inside the phagocyte break down the pathogen in order to destroy it.

  
• ANTIBODY PRODUCTION:

  • LYMPHOCYTES identifies the antigens and produce ANTIBODIES.
  • When a pathogen is marked, it makes it easier for PHAGOCYTES to find them and engulf them.

  
• Once all of the pathogens of a disease have been killed:

  • most of the lymphocytes that produced the antibodies to kill them die off as they are no longer needed.
  • However a few lymphocytes still remain in the body, just in case the pathogen REAPPEARS.

  
• Memory cells


  Are the lymphocytes that remain and produce more antibodies rapidly, so the pathogens die off quickly before the symptoms of the disease have appeared.

  • If this occurs, we say that the person is IMMUNE to the disease and pathogen.

  
• If pathogens enter the body, the immune system tries to destroy the pathogens by:

  • white blood cells detecting pathogens and kills invading cells.
  • phagocytes engulfs and kills invading cells.
  • lymphocytes producing antibodies, to attach and kill invading cells.
  • they make invading cells clump together, so phagocytes can engulf more pathogens.
  • produce antitoxins to destroy toxins, so less tissue damage and don't fell as ill.
  • produce memory cells, so immune response to later exposure is faster.
• Describe how pathogens cause infections and how the immune system defends the body against these pathogens.


  Bacteria and viruses are pathogens:

  • they reproduce rapidly inside the body
  • Bacteria produce toxins that makes us feel ill.
  • viruses live and reproduce inside cells, causing damage.

  white blood cells help to defend against pathogens by:

  • phagocytosis to engulf pathogen and destroy it.
  • producing antibodies to destroy specific pathogens
  • producing antitoxins to counteract toxins released by pathogens
  • This leads to immunity from that pathogen.
• White blood cells:


  Does has a nucleus, to divide by mitosis.

  • produced in bone marrow.
  • It fights infection and are part of the immune system.
  • It patrols the body, circulating in our blood and tissues
• Phagocytes are a special type of white blood cell, that does phagocytosis.
• ANTITOXIN PRODUCTION:



  These help with BACTERIAL infections:

  • Bacteria produce TOXINS, which cause harm to body cells.
  • ANTITOXINS are substances that Bind neutralize the toxins released by invading bacteria.

  
• Antigen


  It's a protein with a part of molecule

  • it stimulates an immune response.
  • An antibody will bind onto it and try to destroy it.

  For example:

  • toxins
  • cell walls of pathogens 

  would be considered antigens.
• Antibodies:


  A protein produced by B lymphocytes.

  • they have a chemical "fit" to a certain antigens.
  • This acts as a signal to our immune system to destroy the antigen (or the pathogen it is part of).
  • They can neutralize pathogens.

  
• Describe how pathogens cause infections:

  Bacteria and viruses are pathogens:

  • they reproduce rapidly inside the body
  • Bacteria produce toxins that makes us feel ill.
  • viruses live and reproduce inside cells, causing damage.
• The immune system defends the body against pathogens as:

  white blood cells help to defend against pathogens by:

  • phagocytosis to engulf pathogen and destroy it.
  • producing antibodies to bind to specific antigens and acts as a signal for phagocytes to destroy the pathogens.
  • producing antitoxins to counteract toxins released by pathogens.
  • This leads to immunity from that pathogen.
• LYMPHOCYTES


  A special type of white blood cell, that produces a specific type of antibody.

  There are two types:

  • B lymphocytes:
  • make antibodies
  • T lymphocytes:
  • destroys harmful pathogens and by sending signals that help control your immune system's response to threats.

  
• Types of white blood cells:

  • T-cells = Kills diseases
  • B-cells = Produces antibodies
• When a lymphocyte with the appropriate antibody meets the antigen.

  • the lymphocyte reproduces quickly and makes many copies of the antibody to kill the pathogen.
• Lymphocytes first divide, then produce antibodies.

  • it takes a while for it to divide, so that's when we feel symptoms.
  • once it starts to make antibodies, it can't divide anymore.
• In first exposure to pathogen:

  • antibodies are created, but they slowly decrease, as they are fighting against the infection.

  In the 2nd exposure to pathogen:

  • antibodies are produced rapidly.
  • As memory cells were created then it gradually decrease.