Layers of defence

• The body system that prevents and fights disease is called the immune system. It is made up of many organs, tissues and cells working together. The immune system fights both infectious diseases, like measles, and non-infectious diseases, like cancer.
• What is the immune system?


  The immune system is the body's defense against disease. It's comprised of organs, tissues, and cells that collaborate to identify and eliminate harmful pathogens. This system is versatile, combating both infectious diseases such as measles and non-infectious ones like cancer.
• The immune system has three lines of defence. The first line of defence is made up of barriers to prevent infection. The second line of defence is made up of responses to infection that apply generally to all pathogens. The third line of defence provides immunity against specific pathogens
• What is the first line of defense?

  The immune system has three lines of defense to protect the body against pathogens. The system of barriers to prevent pathogens from entering the body is the first line of defense. Pathogens must make it past the first line of defense before they can cause an infection.
• What are the components of the first line of defense?

  -Skin

  -Tears, Saliva, Mucus

  -Stomach Acid

  -Cilia

  -Urine Flow
• How does the skin act as a barrier in the first line of defense?

  Acts as an effective barrier against most pathogens, unless broken by a cut or graze.
• How do tears, saliva and mucus act in the first line of defense?

  Trap pathogens so they can be flushed from the body or swallowed. These fluids contain chemicals also called enzymes. They can kill many types of bacteria by breaking down their cell walls.
• How does stomach acid act in the first line of defense?

  Kills pathogens we swallow before they can cause and infection.
• Cilia are microscopic hairs on cells that line the airways which are part of the first line of defense. They move back and forth, pushing mucus & trapped pathogens out of the airways.
• How does urine flow act in the first line of defense?

  It flushes out pathogens out of the bladder and urethra.
• An infection occurs when pathogens make it past the first line of defence and enter the body. When this happens, the immune system responds in some general ways that treat all pathogens equally. Such general responses to infection make up the second line of defence.
• What are the general responses involved in the second line of defense?

  -Fever

  -Inflammation

  -Phagocytes
• How does a fever act in the second line of defense?

  A fever causes an increase in core body temperature above 38 degrees Celsius, which can slow down or even kill some pathogens, alongside speeding up processes which help the immune system deal with the threat.
• What does inflammation do in the second line of defense?

  Inflammation occurs when redness and swelling occurs and the site of infection due to an increase in blood directed to infected region. Blood contains white blood cells which are specialized fight off pathogens.
• What is the purpose of Phagocytes in the second line of defense?

  Some white blood cells destroy anything that they don't recognize as a part of the body by engulfing it. These blood cells are referred to as phagocytes. They help protect the body by engulfing and destroying pathogens.
• What is pus?

  When dead white blood cells build up at the site of a wound, forming pus.
• Snot

  Snot turns yellow when it contains a large number of dead white blood cells. This is a sign that the body is fighting a respiratory infection.
• When the body is healthy, its core body temperature needs to be kept within narrow limits. Usually, this is about 37°C. If the temperature gets too high or too low, natural mechanisms work to return it to normal. So one change in a system causes another change in the opposite direction. This is called a negative feedback loop.
• What is the third line of defense?

  Develops an effective weapon against a particular pathogen. It can also remember that pathogen if it ever shows up in the body again. It can then use the same weapons to defeat it more quickly.
• What is the main roles of the third line of defense

  The third line of defence identifies the pathogen that has infected the body. It then develops a specific weapon to attack it.

  
  

  The third line of defence builds immunity to a pathogen by developing weapons that target it. If the same pathogen shows up in the body again, the weapons can be used to quickly defeat it.
• Each type of pathogen has its own unique structure.
• What do B cells(specialised white blood cells) do in the 3rd Line of defence

  Identify pathogens
• How do B cells identify pathogens?

  They travel through the bloodstream using pattern recognition receptors to identify pathogens and produce antibodies which are specialized to bind onto the antigens on the pathogen, which neutralize and fight the pathogen. Once an antibody binds to a pathogen, the B cell releases millions of matching antibodies into the blood to fight the pathogen. The B cells also clones itself to form an army.
• After an infection has been defeated, some B cells remain in the blood as memory cells, along with any leftover antibodies. Together, these form your immune system's memory of the pathogen, so if you're infected by the same pathogen again, the third line of defense will respond faster and stronger than it did the first time. It works so fast you don't even get sick. This is what it means when you become immune to the disease.
• Phagocytes are a specialized type of white blood cell that form part of the second line of defence. They engulf pathogens and destroy them.
• Antibodies are special proteins produced by B cells. They can be attached to the surfaces of B cells or sent out into the blood. If they bind to a particular pathogen, they can then identify and attack it.
• B cells are a specialized type of white blood cell that form part of the third line of defence. They produce antibodies to fight specific pathogens that have infected the body.
• The third line of defense is made up of specialized white blood cells called B cells which have protiens called antibodies on thier surfaces, that bind to pathogens to identify them. Each type of pathogen has unique surface markers, which only antibodies with a matching shape can bind to. Once the antibody finds its match, it triggers the B cell to clone itself. The new cell army produces millions of antibodies to fight the pathogen. After the pathogen is defeated antibodies and memory cells remain in the body, providing immunity if the pathogen ever appears again.
• What are the two key functions of antibodies

  -Antibodies on the cell membranes of B cells identify pathogens. They do this by binding to the unique markers on pathogens.

  -Once the type of pathogen has been identified, B cells release antibodies into the bloodstream. The huge number of antibodies circulating in the blood help fight the pathogens. 
• What structure is an anti body

  An antibody is a Y shaped structure
• What is an antigen?

  a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies.