BGE Science Body Defence Lesson 4 Second Lines
BGE Science Body Defence Lesson 4 Second Lines of defence
Starter – try the quiz, on the following slides, to see what you already know! There are 2 questions. For the quiz to work, make sure you view this presentation in ‘present’ mode. Click on the answer you think is correct for each question. Good luck! 7 mins
Question 1 Which of the following are barriers to infection? A. Body hair, mucus and skin B. Mucus, skin and tears C. Body hair, skin and tears D. Body hair, mucus and tears
1. Which of the following are barriers to infection? Your answer: A. Body Hair, Mucus and Skin Correct answer is: B. Mucus, skin and tears ★Tiny hairs in the nose help to stop microbes from entering our lungs but body hairs do not have a role in preventing infection. Click here for the next question
1. Which of the following are barriers to infection? Your answer: B. Mucus, Skin and Tears That’s right! Click here for the next question
1. Which of the following are barriers to infection? Your answer: C. Body hair, Skin and Tears ★Correct answer is: B. Mucus, skin and tears ★ Tiny hairs in the nose help to stop microbes from entering our lungs but body hairs do not have a role in preventing infection. Click here for the next question
1. Which of the following are barriers to infection? Your answer: D. Body hair, Mucus and Tears ★Correct answer is: B. Mucus, skin and tears ★ Tiny hairs in the nose help to stop microbes from entering our lungs but body hairs do not have a role in preventing infection. Click here for the next question
Question 2 Which statement about stomach acid is FALSE? A. Acts as a chemical barrier B. Can kill microbes consumed in water C. Can kill microbes trapped by mucus D. Designed to destroy the stomach lining
2. Which statement about stomach acid is FALSE? Your answer: A. Acts as a chemical barrier False answer is: D. Designed to destroy the stomach lining Cells in the stomach wall produce lots of mucus to protect the stomach lining. Click here for the next question
2. Which statement about stomach acid is FALSE? Your answer: B. Can kill microbes consumed in water False answer is: D. Designed to destroy the stomach lining Cells in the stomach wall produce lots of mucus to protect the stomach lining. Click here for the next question
2. Which statement about stomach acid is FALSE? Your answer: C. Can kill microbes trapped by mucus False answer is: D. Designed to destroy the stomach lining Mucus from the nose can be swallowed and ends up in the stomach. Click here for the next question
2. Which statement about stomach acid is FALSE? Your answer: D. Designed to destroy the stomach lining You’re correct, that’s the false answer! Cells in the stomach wall produce lots of mucus to protect the stomach lining. Click here for the next question
Learning Intentions for this lesson • How does the body respond if a pathogen gets past the first line of defence? • Role of white blood cells • Is it possible to get the same infection more than once? • Who is more at risk if they catch an infection?
Success Criteria ✔I can describe how pathogens can get into the body ✔I can describe the 2 roles of white blood cells in defending the body ✔I can describe what an antigen is ✔I can describe what an antibody is ✔I can explain why antibody action is described as specific ✔I can explain why it is possible to get a viral infection more than once ✔I can state who is most at risk if they get an infection
Key Words Pathogen Aerosols White blood cells Phagocytes Infection Non-specific Antibody Antigen Genetic material Risk Mutate Immunity
Getting past the first line of defence ★ Sometimes disease-causing microbes get past the first line of defence ★ Example: if the skin gets damaged by a cut or wound, this provides an entry point for viruses.
Getting past the first line of defence ★Even when the skin is damaged the blood clots quickly, sealing the cut with a scab to prevent microbes entering.
Getting past the first line of defence ★Viruses that travel in aerosols from coughs or sneezes can survive on the skin or on surfaces. ★The virus cannot multiply on the skin or on surfaces but can be picked up by someone who touches that area.
Getting past the first line of defence ★ Once on the hands, the virus can then be transferred into the nose and eyes by the fingers. ★ Viruses in the eye are washed down the tear duct into the nose and into our bodies.
Getting past the first line of defence ★ Use this information to complete this part of Worksheet 4 3 mins
The Blood The two main cells in the blood are: ★ red blood cells and ★ white blood cells.
Second line of defence - white blood cells ★ White blood cells clip.
Second line of defence - white blood cells ★ There are several types of white blood cells. ★ One type called ‘phagocytes’ notice anything foreign or strange that gets through the first line of defence.
Second line of defence - white blood cells ★Phagocytes move towards the foreign object (e. g. microbe), surround it and then destroy it.
Second line of defence - white blood cells This short clip shows white blood cells (phagocytes) attacking bacteria (coloured green)
Second line of defence - white blood cells ★Phagocytes are known as non-specific because they will attack ANYTHING that is foreign to the body. ★They also trigger swelling and redness by sending more blood to the area.
Second line of defence - white blood cells ★ Use this information to complete this part of Worksheet 4 3 mins
Antigen ★All cells have distinctive markers called antigens on their surface. ★When a microbe enters the body, the antigens on the microbe’s surface will allow the body to recognise that it is foreign.
White Blood cells and antibodies ★ A second type of white blood cell recognises foreign antigens. ★ They respond by producing substances called antibodies. ★ Antibodies are Y-shaped molecules. ★ The shape of each antibody type matches the shape of an antigen and so they are described as being specific.
White Blood cells and antibodies Antigen A Antigen B Antibody 1 ★ Antibody 1 will target only antigen A. ★ Can you explain why antibody 1 will not target antigen B?
White Blood cells and antibodies ★Antibodies attach to the antigen on the microbe and destroy it. ★These antibodies will ONLY target these specific markers/antigens and no others. ★Your body will make extra white blood cells to destroy the microbe.
Summary of Antibody Action
Immunity ★Once the microbes have been killed, your body will recover from the infection and the numbers of white blood cells will return to normal levels. ★Some white blood cells, that make the same antibody, will stay in your body as memory cells.
Immunity ★If the same antigen infects the body again, these white blood cells destroy the microbe before it has a chance to make you ill. ★This is why we don’t usually catch the same disease twice - we are described as being immune.
Antibodies and Antigens ★ Use this information to complete this part of Worksheet 4 6 mins
Viruses can mutate ★Remember in lesson 2 you learnt about the structure of a virus? ★Viruses contain genetic material and it can be DNA or RNA.
Viruses can mutate ★Viruses have a superpower! ★They can change the structure of their genetic material - this is called a mutation. ★The new genetic material of a virus will mean the antigen on this altered virus is different.
Viruses can mutate ★Our memory cells will not recognise these new antigens as they are different and so the whole process of making new antibodies has to start again from scratch.
Viruses can mutate ★There are several strains of the cold virus (Rhinovirus), each with different antigens. ★This is why you can catch several colds each year. ★In fact, each infection is caused by a different strain (mutation) of the cold virus. ★It is thought that immunity to the common cold only lasts about 6 months.
Virus superpowers! ★ Use this information to complete this part of Worksheet 4 6 mins
Who is more at risk if they catch an infection? ★Babies and young children – their immune system is not yet fully developed. ★The elderly – their immune system no longer functions as well. ★People who are already ill – their immune system is already working very hard.
Who is most at risk of infection? ★ Use this information to complete this part of Worksheet 4 6 mins
Plenary Complete the plenary on Worksheet 4. 6 mins
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