1. Biology in Focus, HSC Course Glenda Childrawi, Margaret Robson and Stephanie Hollis A Search For Better Health Topic 7: First Line of Defence

2. DOT Point(s) identify defence barriers to prevent entry of pathogens in humans: skin mucous membranes cilia chemical barriers other body secretions world.edu

3. Introduction Just like the defence forces that protect our country, the human body has a number of different defence mechanisms, to protect itself from invasion by foreign organisms. The human bodies first line of defence is to try to prevent the entry of foreign organisms into the body. www.dsto.defence.gov.au

4. Introduction If these organisms succeed in getting past the barriers to their entry, the second line of defence then tries to destroy them quickly before they can cause any problems for the body. Both of these types of defence are non-specific, meaning that they are directed against a wide range of invaders. www.timesofmalta.com

5. Introduction If these invaders manage to survive both the first and second line of defence, then the third line of defence, the immune response, is activated. This is now getting serious; the response is specific to the particular invader and involves an attack from a number of different directions. www.walgreens.com

6. Introduction The symptoms of a disease allow us to recognise the disease, and our recovery from the disease indicates that our immune system has successfully defended our body and overcome the pathogens. www.fitango.com

7. First Line of Defence The first line of defence is a nonspecific defence and involves the body using both physical and chemical barriers to try to prevent the entry of pathogens into the blood and tissues.. www.appliedsafety.net.au

8. First Line of Defence The most vulnerable areas on the body for the entry of the pathogens are the openings, such as the mouth and nose, and the internal passages, such as the alimentary canal and the urinogenital tract. americankabuki.blogspot.com

9. First Line of Defence Barriers include: The skin Mucous membranes Cillia Chemical barriers Other body secretions www.fitango.com

10. First Line of Defence The Skin – a physical barrier The skin forms a tough outer barrier that covers the body and prevents penetration by microbes. It is fairly dry, which helps to prevent the growth of pathogens. www.lilsugar.com

11. First Line of Defence The skin also contains its own population of harmless bacteria that help to stop the invading microbes from multiplying. Oil and sweat glands in the skin produce antibacterial and antifungal substances that further inhibit the growth of invading pathogens. commons.wikimedia.org

12. First Line of Defence If the continuous barrier of the skin is cut, the blood clots almost immediately to produce a temporary patch to maintain the barrier until new skin forms. en.academic.ru

13. First Line of Defence Mucous membranes The respiratory, digestive, reproductive and urinary tracts are covered with membranes that produce a thick layer of mucus which traps the entering pathogens. The pathogens are held in the mucus until they are removed by processes such as coughing and sneezing. www.betweenbabies.com

14. First Line of Defence The mucus can contain an antibody that prevents bacteria and viruses from attaching to the surface. The mucus also provides a moist, nutritious layer in which the harmless microbes live and produce substances that inhibit the growth and entry of pathogens. www.obfocus.com

15. First Line of Defence Cilia Cilia are tiny ‘hairs’ that line the respiratory surfaces of the trachea and bronchial tubes. The cilia are constantly beating in an upwards direction to move the mucus containing the trapped pathogens towards the throat, where they are removed by coughing, sneezing or swallowing. www.digitalblasphemy.com

16. First Line of Defence Chemical Barriers Different types of chemicals secreted in different parts of the body act as a barrier to the invading pathogens. In the alimentary canal, pathogens entering with food or drink, or swallowed with mucus, will be destroyed by the acidic conditions of the stomach or the alkaline conditions in the intestines. www.heraldsun.com.au

17. First Line of Defence The urinary and vaginal openings and the surface of the skin are also acidic, which inhibits the growth of pathogens. rationalpreparedness.blogspot.com

18. First Line of Defence Other body secretions Urine is sterile and slightly acidic and flushes and cleans the ureters, bladder and urethra. It helps to prevent the growth of microorganisms. www.ocweekly.com

19. First Line of Defence Other body secretions Tears contain lysozymes that destroy the cell walls of some bacteria. As the tears are produced and the eyelid blinks, the surface of the eye is cleaned and the pathogens are washed away. my.englishclub.com

20. First Line of Defence Other body secretions Saliva also contains lysozymes and washes micro-organisms from the teeth and the lining of the mouth. www.thefastertimes.com

21. Homework -Students to complete 7.1.2 First Line of Defence Barriers Activity