Human Defences Flashcards
what are the 2 types of human defences
chemical defences
physical barriers
what are chemical defences
a chemical produced that is used to kill or make pathogens inactive
what is the purpose of physical barriers
make it hard for pathogens to enter the body
what are 2 chemical defences
lysozyme enzyme in tears and saliva
hydrochloric acid in the stomach
what are 2 physical barriers
skin
mucus
how is the lysozyme enzyme a chemical defence
it breaks down bacteria cell walls
how is hydrochloric acid a chemical defense
it kills pathogens in foods and drinks
how is skin a physical barrier
it forms a protective barrier that is too thick for most pathogens to get through
where is sticky mucus found
in the breathing passages and lungs
how does sticky mucus work
they trap pathogens, the cilia on the cells lining the lungs will move in a wave-like motion moving mucus and trapped pathogens out
what are the 2 types of white blood cells
lymphocytes and phagocytes
what are phagocytes
white blood cells that are not specific that engulf pathogens
how do lymphocytes work
every pathogen has unique antigens. the body mutates lymphocytes to create a lymphocyte that has antibodies that fit the antigens. once the correct lymphocyte is found it will divide to produce more of them. they will release lots of antibodies which will stick to the pathogen and destroy it
how do lymphocytes deal with secondary infections
some of the lymphocytes will stay in the blood as memory lymphocytes so that they are ready to respond immediately if the pathogen returns
what is immunisation
when a person is given a vaccine to prevent them from becoming ill
how do vaccines work
- a vaccine contains antigens from the pathogen, often in the form or dead or weakened pathogens
- the person’s lymphocytes produce antibodies against the pathogen and also memory lymphocytes
- when the person becomes infected for real, the memory lymphocytes will give a very rapid secondary response to the pathogen as it already has the memory lymphocytes. this will prevent the person from becoming sick
what are 3 advantages of immunisation
immunity can be produced without being ill
lasts a long time
herd immunity
what is herd immunity
when most of the people in a community are vaccinated the unvaccinated people are less likely to catch the disease. as the disease will be contained
what are 2 negatives of immunisation
some people get a mild reaction
very rarely a person as a major harmful reaction
