Planet Earth and Its Environment A 5000-million year Journey

Biology in Focus, HSC CourseGlenda Childrawi, Margaret Robson and Stephanie Hollis

A Search For Better HealthTopic 7: First Line of Defence1DOT Point(s) identify defence barriers to prevent entry of pathogens in humans:skinmucous membranesciliachemical barriersother body secretionsworld.eduIntroductionJust 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

IntroductionIf 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 IntroductionIf 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

IntroductionThe 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

First Line of DefenceThe 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

First Line of DefenceThe 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

First Line of DefenceBarriers include:The skinMucous membranesCilliaChemical barriersOther body secretionswww.fitango.com

First Line of DefenceThe Skin a physical barrierThe 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

First Line of DefenceThe 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

First Line of DefenceIf 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

First Line of DefenceMucous membranesThe 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

First Line of DefenceThe 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

First Line of DefenceCiliaCilia 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

First Line of DefenceChemical BarriersDifferent 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

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

First Line of DefenceOther body secretionsUrine 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

First Line of DefenceOther body secretionsTears 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

First Line of DefenceOther body secretionsSaliva also contains lysozymes and washes micro-organisms from the teeth and the lining of the mouth.www.thefastertimes.com

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