4.3.1.6 – human defence systems

what are the non-specific defence systems of the human body against pathogens

• skin

• nose

• trachea and bronchi

• stomach

how does this skin work as a defence system

• a physical barrier to pathogens

• secrets antimicrobial substances which kills pathogens

how does the nose work as a defence system

• hair and mucus in nose trap pathogens and prevent them from entering the respiratory system

how do the trachea and bronchi work as a defence system

• they are lined with cilia and mucus

• the cilia waft their hairs and move mucus and pathogens upwards towards the throat where it is swallowed into your stomach

• goblet cells produce mucus which trap pathogens and prevent them from entering the respiratory system
  

how does the stomach work as a defence system

• the stomach produces hydrochloric acid which kills pathogens which make it far from the mouth

immune system

• the body's defence system against entry of any foreign body, including pathogens and agents such as pollen grains

• the role of the immune system is to prevent disease

what happens when a pathogen enters the body

• if a pathogen enters the body the immune system tries to destroy the pathogen

what does the immune system comprise of

• white blood cells

how do white blood cells help to defend against pathogens?

• phagocytosis

• antibody production

• antitoxin production

what is phagocytosis

• phagocytes surround any pathogens in the blood and engulf them

• they are attracted to pathogens and bind to them.

how does phagocytosis work

• phagocytes engulf and digest pathogens, this can be non-specific or helped by antibodies which cause agglutination (clumping) of pathogens

• the phagocyte surrounds the pathogen and releases enzymes to digest and break it down to destroy it

which white blood cells produce antibodies

lymphocytes

what are antibodies

• a protein made by lymphocytes that is complementary to an antigen and, when attached, clumps them together and signals the cells they are on for destruction

what is the aim of antibody production

• the aim of antibody production is to produce the antibody that is specific (complementary) to the antigens on the surface of the pathogen

• the antibodies produced are specific to each pathogen's antigens

what are memory cells

• lymphocytes that remain in the body after an initial infection with a particular pathogen

• they produce the specific antibodies against its antigens so that if you get infected by the same pathogen again in the future (and the antigens are the same) you can produce antibodies much quicker against it

how are antibodies transported through the body

through plasma

what are antitoxins

a protein that neutralises the toxins produced by bacteria

what produces antitoxins

lymphocytes