How our bodies defend themselves against infectious diseases

Pathogens are microorganisms that cause infectious diseases. 

Bacteria:

- Reproduce rapidly in our body. 

- Produce toxins which make us feel unwell.

Viruses:

- Reproduce inside cells. 

- When released, they damage cells making us unwell. 

White blood cells protect us from pathogens. 

White blood cells ingest pathogens and destroy them. 

White blood cells produce antibodies which destroy particular bacteria or viruses. 

White blood cells produce antitoxins which counteract toxins released by pathogens. 

Semmelweis was a doctor in the 1800's. In those times, a lot of women died after childbirth from 'childbed fever'. Semmelweis looked closely at how many women were dying at different parts of the hospital. 

There were two main wards; one ran by doctors (Ward A), the other by nurses (Ward B). 

Semmelweis noticed that in ward A, a large number of women died from childbed fever and on ward B the death rate was much lower. 

In ward B, the nurses only worked with pregnant women and NEVER dealt with dead bodies. 

In ward A, the doctors often examined dead bodies and then went straight from there to working with pregnant women. Doctors never washed their hands after examining bodies, so Semmelweis wondered if they were spreading fever on their hands.

Semmelweis told doctors to wash their hands in disinfectant before working with pregnant women. After they did this, the death rate decreases rapidly. However, it took a long time before all doctors understood the importance of handwashing and hygiene because they didn't understand that infectious diseases were spread by pathogens. 

Once we fight off a pathogen, we are immune. Immunity is specific. 

MMR Vaccine (measles, mumps, rubella)

When someones vaccinated, they're given a dead or inactive pathogen, so that the person will not actually get the disease. 

White blood cells then produce antibodies against the dead/inactive pathogen. 

At the same time, the white blood cells reproduce. 

This is so that if you get the live pathogen in the future, antibodies can be produced rapidly as the body already knows what to do. 

It's important that a large number of people are vaccinated against disease because there are always some people who don't get vaccinated. If lots of people are vaccinated, it protects unvaccinated people too. 

Culture of bacteria = population of bacteria.

Culturing = growing.

Equipment:

- Petri dish 

- Innoculating loop 

- Agar jelly