Understanding the 3 Levels of Human Defence Against Pathogens

N3 Science Human Health Human Defence

N3 Science Human Health Human Defence Success Criteria I will know the 3 levels of defences prevent microbes getting in.

N3 Science Human Health The 3 Levels of Defence The Human body has 3 Lines of Defence Against Invading Pathogens 1. Physical and Chemical Barriers 2. Nonspecific Resistance 3. Specific Resistance

N3 Science Human Health Watch this clip which gives some information on how these defence systems work https://www.youtube.com/watch?v=aq-F4rNuj3Y

N3 Science Human Health First Line of Defence The body is constantly defending against attacks from pathogens. The first line of defence against infection stops the pathogens from entering your body. These first lines are general defences and are not specific to fight against certain types of pathogen. They are called non-specific and are physical or chemical barriers.

N3 Science Human Health The first line of defence is non-specific. It works against any type pf disease-causing agent. Tears antibacterial enzymes Saliva antibacterial enzymes Skin Mucus linings traps dirt and microbes prevents entry Stomach acid low pH kills harmful microbes Good gut bacteria out compete bad

N3 Science Human Health Second Line of Defence The second line of defence is also nonspecific. When the invading microbes get past the first line of defence, special White Blood Cells called Phagocytes ingest them and destroy them.

N3 Science Human Health Copy and complete using the word bank Word bank All Inside Phagocytes Microbe Digests Response White Cells Second Line of Defence There is a group of ________ cells that are found in blood called _________________. These white __________are able to surround the invading _____________ and trap it. Once the microbe is ____________ the phagocyte, it ___________ it. This is called a non- specific ____________. It is the same response for ________pathogens

World of Microbes Check your answers Word bank All Inside Phagocytes Microbe Digests Response White Cells Second Line of Defence Invading Microbe There is a group of ________ cells that are found in blood called white _________________. These white __________are able to Phagocytes cells surround the invading _____________ and trap it. Once the microbe microbe is ____________ the phagocyte, it ___________ it. This is inside digests Phagocyte called a non- specific ____________. It is the same response for response ________pathogens. all

N3 Science Human Health Third Line of Defence A lymphocyte is another type of white blood cell that is part of the immune system. There are two main types of lymphocytes - B cells and T cells. The B cells produce antibodies that are used to attack invading bacteria, viruses, and toxins. B cells produce antibody molecules that can latch on and destroy invading viruses or bacteria. The T cells destroy the body's own cells that have themselves been taken over by viruses or become cancerous.

N3 Science Human Health Third Line of Defence Production of Antibodies By Lymphocytes This is a specific response. The antibodies produced in response to one particular microbe will only work against that specific Microbe.

N3 Science Human Health Copy and complete using the word bank Word bank Surface Specific Lymphocyte Antibodies One Fighting Phagocytes Third Line of Defence The third system for ___________ microorganism is provided by a different group of white blood cells called _________________. These white blood cells produce special _____________ which bind to the ______________of the invading microorganism and destroy it. ______________ then eat up the debris. Antibodies are ______________so each type will only work against _____________ type of invading microbe.

N3 Science Human Health Check your answers Word bank Surface Specific Lymphocyte Antibodies One Fighting Phagocytes Third Line of Defence The third system for ___________ microorganism is provided by a different group of white blood cells called _________________. These white blood cells produce special _____________ which bind to the ______________of the invading microorganism and destroy it. ______________ then eat up the debris. Antibodies are ______________so each type will only work against _____________ type of invading microbe. fighting Lymphocytes antibodies surface Phagocytes specific one