Biology Notes 2nd Term

Biology Notes 2nd Term - Chapter 33 How the Animal Body...

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Chapter 33 How the Animal Body Defends Itself A. Three Lines of Defense 1. Skin – the skin protects the body from pathogen invasion 2. Cellular Counterattack – the second line of defense against invasion is provided by a host of nonspecific cellular and chemical defenses 3. Specific Immunity – T and B cells provide the body’s third line of defense Antigen – any molecule that is foreign to a white blood cell and triggers or causes an immune response Every person has a different self marker Your immune system recognizes it and does not attack Anything that does not have the same marker will get attacked Antigens on surface of virus tell immune system to attack since it does not have the same self marker Antibody – is a Y shaped protein composed of 4 polypeptides (2 heavy chains and 2 light chains) V – variable C – constant Higher part of polypeptide is variable Lower part of polypeptide is constant Your body is able to make millions of antibodies through the variability region Disulfide bridges – holy polypeptide together Epitope – region of antigen where the antibody will attach to Immunity – resistance to a specific invader obtained by infection or by vaccination (when you get a harmless sample of virus) Active Immunity – you made the antibodies yourself and generally last life time (LONG TERM) Passive Immunity – you receive the antibodies already made (ex. Mother to fetus); only last couple of months (SHORT TERM) v v v v c c c c
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Autoimmune Diseases – immune system gets confused wand starts attack self as it is non-self (ex. Attacking pancreas with diabetes) Severe Combined Immune Deficiency – critical cells of immune system are not produced and missing First Line of Defense The skin produces lysozyme, which go after bacteria and destroys their cell wall Skin is very acidic (pH of between 4 and 5.5) which inhibits the growth of many microbes Tears contains lysozymes which bathe the eyes and fight bacterial infections Microbes are present in food, but many are killed by saliva (which also contain lysozyme), by the very acidic environment of the stomach (pH of 2), and by the digestive enzymes in the intestine Microbes also enter body through the air, but the cells lining the smaller bronchi and bronchioles secrete a layer of sticky mucus that traps most microorganisms before they can reach the warm, moist, lungs, which would provide idea breeding grounds for them. Other cells lining these passages have cilia that continually sweep the mucus up toward the glottis in the throat, where it can be swallowed, carrying potential invaders out the lungs and into the digestive tract Second Line of Defense The lymphatic system consists of structures: lymph nodes, lymphatic organs, and a network of lymphatic capillaries that drain into lymphatic vessels The three basic kings of killing cells are macrophages and neutrophils, which are phagocytes, and natural killer cells. Each uses a different tactic to kill invading microbes.
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Biology Notes 2nd Term - Chapter 33 How the Animal Body...

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