B1 Topic 3: Defence Against Disease L/O: To examine ways the body defends itself against disease. S/C: EBI: Evaluate the differences in defence between humans and plants. Great: Explain physical and chemical ways in which the body defends against specific diseases. Good: Describe how micro-organisms can get into the body.

How do pathogens get into the body? Draw a person and annotate.

ears eyes Nose and mouth Cuts or bites genitals

How does the body defend itself against disease? Around the room are some fact sheets explaining how the body protects itself. You have 15 minutes to understand how the body defends itself against disease. Either make revision notes or further annotate your person. EXTRA CHALLENGE: What diseases may be prevented by these defences? (think of mode of transmission).

How are plants different?

How are plants different?

How are plants different? Nettles have adapted to have acid in their spines. This protects them against predators.

How are plants different?

How are plants different? Mint, tea tree and witch hazel all have anti- bacterial properties. Humans now use these plants for their own purposes.

What happens when the natural defences don’t work? How do humans work to prevent disease?

Why did so many people used to die from minor illnesses and minor surgery?

A young child goes to school for the first time A young child goes to school for the first time. Soon after, the child gets a cold and a sore throat. (a) Explain, as fully as you can, what causes the child’s illness. (2) (b) The doctor tells the child’s mother that children often get ill when they start school and mix with other children. Why is a child more likely to get an infectious illness when he or she starts school? (1) (c) The child gets better without taking any medicine. Explain how. (Total 4 marks)

(b) contact with infected people for 1 mark           (a)     microbes entered body,  multiplied rapidly, made poisons any 2 for 1 mark each 2 (b)     contact with infected people for 1 mark 1 (c)     the body kills the microbes [4]  

An investigator placed paper discs containing different concentrations of an antibiotic onto a culture of bacteria in a Petri dish. After an incubation period of two days, the dish looked like this. (i) Explain why there are areas around some of the paper discs where no bacteria are growing (2)

(iii)    Use the table to describe the effect of an increase in the concentration of the antibiotic on the growth of the bacteria. (2) (iv)     The results of the investigation did not show the best concentration of antibiotic to kill the bacteria. Describe how the experiment could be improved to find the best concentration.

(b) (i) because antibiotics diffuse / pass (into agar) 1 where they kill bacteria (ii)     as a control (iii)    as the concentration increases more bacteria are killed or causes less growth levels off (at 6 units) or the greatest effect is when the concentration is increased from 4 to 6 units (iv)     repeat experiment with more concentrations of antibiotic between 4 and 6 units

Scabs are formed from blood clotting. When you get a wound special blood cells called platelets stick together and react with other proteins to build a clot. This clot is made from a stringy protein that stretches across the wound, pulls the edges together and plugs the gap between them. This helps to stop any more blood from escaping, but also stops bacteria getting in.

TEARS & EYE-LASHES Your eye-lashes act as a barrier which protects the eye when it is open. They trap dirt and microorganisms preventing them from entering the eye and causing infection. Tears have lysosomes (organelles that release enzymes) that essentially desiccates or "dries up" microorganisms. They also help wash out any microorganisms that enter the eye, keeping it clean.

STOMACH ACID Your stomach contains an acid called hydrochloric acid (HCl). This acid is used to breakdown food, it has a pH of 2 and is very corrosive. Helicobacter pylori is the only bacteria which can survive the acidic conditions in our stomach. The stomach is coated with a special lining to prevent the acid corroding the wall away. However any microorganisms that enter our body though our nose/mouth end up in the stomach & its acid, which then destroys their cell walls and kills them.

HAIRS IN OUR NOSE Hair in the nose is one of the body's first lines of defence against microorganisms. When you breathe in oxygen, you are also breathing in whatever solid particles are contained in that air. The hair contained in the nostrils helps to trap the larger particles in a sticky layer of mucus (snot). This is can then be removed from the nose through blowing or swallowing the mucus, which is then taken care of in the stomach.

SKIN Our skin is our bodies large organ and first line of defence. The different layers of skin literally block microorganisms like a force-field. Microorganisms, especially bacteria, live on our skin because it cant get in. The top layer (dead epidermis) sheds all the time. Getting rid of old skin means we are also getting rid of a lot of the microorganisms and bacteria with it. This keeps them from staying on our bodies too long.

TRACHEA - CILIA There are some specially adapted cells in our trachea (windpipe) which contain cilia (hair like projections). As you can see from the picture, there are mucus producing cells mixed in with the ciliated cells to help keep a fresh lining of mucus in our airways. This sticky layer of mucus traps the majority of microorganisms and large particles which enter our body. The cilia sweep the mucus containing the trapped microorganisms into the stomach.