Micro Topic 9 - TOPIC 9 MICROBIAL DISEASES OF THE SKIN AND EYES(Chapter 21 1 STRUCTURE AND FUNCTION OF THE SKIN(Figure 21.1 pg 591 A SKIN a The

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TOPIC 9: MICROBIAL DISEASES OF THE SKIN AND EYES (Chapter 21) 1. STRUCTURE AND FUNCTION OF THE SKIN (Figure 21.1 pg 591) A. SKIN a) The skin is the largest organ in the body. b) It consists of two parts: i) The epidermis: i. Thin outer portion: several layers of dead epithelial cells. ii. Contains waterproof keratin that prevents water-soluble substances from entering the body. ii) The dermis: i. Thick inner portion composed of connective tissue. ii. Contains sweat glands, oil glands and hair follicles, which are potential portals of entry for microbes. c) Perspiration (from sweat glands) and sebum (from sebaceous glands) provide moisture and nutrients for microbial growth. d) Sebum and perspiration also have some anti-microbial properties – high salts and acidic pH. B. MUCOUS MEMBRANES a) Consist of tightly packed epithelial cells, attached to a basement membrane. b) Line those tissues and organs that open to the outside of the body e.g. respiratory, digestive and urogenital systems. c) Many of the cells secrete mucus (thick, watery secretion of glycoproteins and electrolytes), hence the name mucous membrane or mucosa. d) Mucus forms a protective layer over epidermal cells, preventing desiccation. e) Also traps pathogens before they establish an infection. f) Mucosa are often acidic, limiting microbial growth. g) Some mucosal cells have cilia – ciliatory escalator. 2. NORMAL MICROBIOTA OF THE SKIN a) Skin is relatively dry and acidic – prevents growth of most microbes. b) Some microbes can grow on the skin, and can metabolize oils, creating an acidic pH that prevents the growth of other, pathogenic bacteria (also creates unpleasant odor). c) Microbes exist in hair follicles, sweat glands and moister areas such as armpits. d) Most common normal flora of the skin is Staphylococcus sp., which grow well in salty conditions. e) Also found in the normal flora are Micrococcus sp and Corynebacteria. 3. MICROBIAL DISEASES OF THE SKIN (figure 21.1 pg 592) 1
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a) Few bacteria can penetrate the intact skin. b) However, broken skin and mucous membranes are more easily penetrated. c) Many systemic diseases manifest with skin lesions. These include: a. Vesicles: small fluid-filled lesions b. Bullae: large vesicles c. Macules: flat red lesions d. Papules: raised lesions e. Pustules: papules containing pus d) Skin also exhibits rashes: a. Exanthem: rash on skin arising from disease b. Enamthem: rash of the mucous membrane A. BACTERIAL DISEASES OF THE SKIN 1. Staphylococcal skin infections (Figure 21.4 pg 595) a) These are gram-positive bacteria that cluster like grapes. b) Can be divided into those that produce coagulase (coagulase positive) and those that don’t (coagulase negative). a.
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This note was uploaded on 04/07/2008 for the course BIOLOGY BIO230 taught by Professor Prof.? during the Spring '08 term at Borough of Manhattan Community College.

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Micro Topic 9 - TOPIC 9 MICROBIAL DISEASES OF THE SKIN AND EYES(Chapter 21 1 STRUCTURE AND FUNCTION OF THE SKIN(Figure 21.1 pg 591 A SKIN a The

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