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L2: The Body’s Natural Defenses BIG QUESTION: What is the body’s first line of defense against bacteria and germs? WARM-UP: Make a list of all the ways in which a germ or foreign particle might get into the body. (p. 54 of Journal – title “Body’s Natural Defenses”) Lesson Objectives: SWBAT •Describe the body’s natural defenses •Explain how each defense protects the body •Create a specialized germ that would be able to penetrate these defenses. L2: The Body’s Natural Defenses The human body has natural defenses which prevent foreign particles and germs from entering the body. 1. How can germs and foreign particles enter the body? Share your answers. FORGET IT! WE NEED TO FIND A WAY INTO THE BODY! L2: The Body’s Natural Defenses The human body has natural defenses which prevent foreign particles and germs from entering the body. 1. How can germs and foreign particles enter the body? Share your answers. • The mouth and nose • Any open hole, including the ears, anus • Sores and cuts • Exposed tissue from piercings • The eyes Ahh, I see an opening! Oh Boy! Me and my big mouth! L2: The Body’s Natural Defenses There are 6 natural body defenses which help defend our body from foreign particles these include the SKIN, TEARS, SALIVA, MUCUS, HAIR and STOMACH ACID. The skin is my main barrier L2: The Body’s Natural Defenses THE SKIN The SKIN this is the major barrier to foreign particles. Its outer layer is tough, it also contains sebaceous glands which secrete oil (sebum) which help kill bacteria. The skin is the body’s largest organ L2: The Body’s Natural Defenses THE SKIN The surface of the skin is constantly being renewed, the top layer is replaced about every 27 days. The oil glands, sometimes referred to as the sebaceous glands release oil. This oil (sebum) contains some antibacterial qualities, killing bacteria. The skin also contains special cells called “Langerhans Cells”, which detect foreign particles, they then present these particles (their antigens) to the immune system which will decide what to do. L2: The Body’s Natural Defenses TEARS The EYES, although they are not holes, do allow foreign particles or bacteria to enter the body. The eyes are therefore protected by TEARS. If you ever get something in your eye you might notice that your eye starts to water, this is a natural defense mechanism. My Eyes are burning Tears produced here L2: The Body’s Natural Defenses TEARS The tears, contain a chemical called Lysozyme, this chemical kills microorganisms (small living things). This process is sometimes accompanied with the release of mucus, which can capture foreign particles, the mucus then hardens and accumulates in the corner of your eye. QUICK RUN! Tears produced here SHE HAS GOT TEARS! L2: The Body’s Natural Defenses SALIVA Your mouth is huge , some people’s mouths are bigger than others!! The facts is that the mouth is a great way for bacteria and other germs to enter the body. Luckily for us we have SALIVA. SALIVA: is the liquid that is produced naturally in our mouth. It plays an important role in the digestion of food, but also in killing germs. These germs make my mouth water L2: The Body’s Natural Defenses SALIVA SALIVA contains the same chemical that is found in tears, Lysozyme. If something enters our mouth the Lysozyme chemicals get to work destroying the germs. Lysozyme in saliva I am out of here! HELP ME! I’m MELTING….. L2: The Body’s Natural Defenses MUCUS MUCUS is that gross sticky stuff that runs from your nose. MUCUS: Is found in the nose and respiratory system. It sticks to foreign particles and microbes. Some mucus contains white blood cells which can call for back up or handle the infection on the spot. Stay away I have got mucus in my nose! MUCUS In the respiratory system, the mucus is secreted from tiny structures called Goblet cells, which are located in the lining of the trachea (wind pipe). Mucus secreted by goblet cell Goblet Cell MUCUS The mucus is carried to the top of the trachea by a column of ciliated epithelia. Column of Ciliated Epithelia Goblet Cell Trachea ZOOM Mucus secreted by goblet cell Cilia moves mucus away from lungs Mucus traps dust particles and it is swept to the top of the trachea MUCUS The cilia beat back and forth carrying the mucus and germs upwards. dust germs mucus cilia Ciliated epithelium Mucus, germs and dust moves along like a conveyor belt MUCUS If mucus was not produced by the goblet cells dust, germs and other particles might become lodged within the airways, which could result in an infection. Foreign Bodies Goblet Cell COUGH COUGH COUGH HAIR L2: The Body’s Natural Defenses HAIR: Tiny hairs in the nose, ear, and pubic area can help keep unwanted particles out of the body. They are also a great place to catch mucus which might contain foreign particles. NOSE HAIR You are no match for my nose hair! That nose hair is scary!! Lets think of another plan! L2: The Body’s Natural Defenses STOMACH ACID STOMACH ACID: The stomach contains Hydrochloric Acid which kills microorganisms. If you eat something that contains bacteria, or other microorganism the acid should destroy it. My acid will destroy you little germ! ACID L2 The body’s Natural Defenses: ACTIVITY 1. The body has many natural defenses, however the fact that we get sick means that these defenses are not 100% effective. Using a decision tree* (next slide), Imagine that you were a germ, what would be the best way to enter the body. Create 3 solutions, for each solution list the pros and cons, then based on your evidence explain which is the best solution and why. . 2. If you could remove one natural defense to make it easier for germs to enter the body, which defense would it be and why? Include explain and support your argument with evidence 3. Design the ultimate germ. Create a sketch of the ultimate germ, annotate your sketch to explain what features it has to help it get past the body’s natural defenses. You may draw your own or use the templates below to help you. 19 THE DECISION TREE BEST SOLUTION and WHY: SOLUTION #2 SOLUTION #3 PROS PROS PROS CONS CONS CONS STATE THE PROBLEM: Biologyguy © SOLUTION #! 20