Micro Topic 7 - TOPIC 7: IMMUNOLOGY (ch 16-19) a) The...

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TOPIC 7: IMMUNOLOGY (ch 16-19) a) The ability to avoid disease is resistance. Lack of resistance is susceptibility. b) There are 3 lines of defense (figure 16.1 pg 459) a. First : skin, mucous membranes, normal flora. b. Second : phagocytic white blood cells, inflammation, fever, antimicrobial substances (complement and interferons). c. Third : specialized lymphocytes (B cells and T cells). c) The first and second lines of defense are non-specific and protect the body against any kind of pathogen. d) The third line of defense is specific and acts against specific microbes. 1. FIRST LINE OF DEFENSE – non specific defenses A: Skin and mucous membranes a) Protect by mechanical and chemical factors: a. Mechanical factors: i. Tightly packed cells, ii. Keratin, iii. Dryness, iv. Periodic shedding, v. Mucus, vi. Washing action of tears, saliva, urine and vaginal secretions, vii. Cilia b. Chemical factors: i. Sebum ii. Perspiration iii. Lysozyme iv. Gastric juice v. Transferrins B: Normal microbiota a) Protect body from pathogens by: a. Environmental changes e.g. pH – makes the internal environment unfavorable for invading microbes. b. Competitive exclusion – normal flora competes with invading microbes for nutrients etc. c. Bacteriocins – toxins that kill bacteria. 2. SECOND LINE OF DEFENSE – non-specific defenses A. White blood cells and phagocytosis a) Phagocytosis is the ingestion (eating) of microbes or other particles by a cell, specifically a white blood cell called a phagocyte. b) There are two main categories of WBC (Figure 16.5 pg 464): a. Granulocytes: neutrophils, basophils and eosinophils 1
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b. Agranulocytes: monocytes, macrophages and lymphocytes (B and T cells) c) Neutrophils, eosinophils and macrophages have a phagocytic function. a. Neutrophils and monocytes migrate to site of infection. b. Monocytes develop into macrophages: i. Fixed ii. Wandering d) Phagocytosis has the following steps (Figure 16.8 pg 467): a. Chemotaxis : attraction of phagocytes to microbe. b. Adherence : attachment of phagocyte to surface of microbe. c. Ingestion : “eating” of microbe by phagocyte by pseudopods and formation of phagocytic vesicle and then phagolysozome . d. Digestion : breakdown of microbe in phagolysozome e. Discharge : release of undigested wastes. e) Some microbes are able to evade phagocytosis e.g. by capsule formation, and can thus cause disease. B: Inflammation (Figure 16.9 pg 470) a) Inflammation is a local response to cell damage. b) It is characterized by redness, swelling, pain, heat and sometimes loss of function . c) Inflammation can be acute (e.g. boil) or chronic (e.g. TB). d) Inflammation: a. Destroys the injuring agent. b. If it does not destroy the agent, it walls it off and isolates it. c.
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Micro Topic 7 - TOPIC 7: IMMUNOLOGY (ch 16-19) a) The...

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