113lecture3506 - BIOLOGY 113 - MICROBIOLOGY Lecture 35:...

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BIOLOGY 113 - MICROBIOLOGY Lecture 35: Microbial Diseases of the Digestive System - Infections of the mouth, bacterial gastroenteritis Most infectious diseases of the gastrointestinal tract are acquired through ingestion of contaminated food or water that contains pathogenic microorganisms or their toxins - The digestive system (Tortora et al., Figure 25.1) may be divided into two groups of organs = The gastrointestinal (GI) tract (which is, in a topological sense, an external surface!) consists of the mouth, esophagus, stomach, small intestine and large intestine. = Various accessory structures , including salivary glands, liver, gallbladder and pancreas, lie outside of the GI tract and produce secretions that are conveyed into the GI tract - The function of the GI tract is to provide conditions for digestion of nutrients and their transfer to the cardiovascular and lymphoid systems for use by cells = The combined action of enzymes produced in the GI tract and accessory structures serves to catalyze hydrolysis of polymers (polysaccharides, lipids, proteins) to their soluble monomers (simple carbohydrates, fatty acids, amino acids) = The small intestine serves the process of absorption of these monomers into the bloodstream = The processes of digestion and absorption require that large amounts of water and electrolytes (salts) be secreted into the GI tract · The large intestine serves the process of resorption of the water and electrolytes secreted during digestion · Dehydration and hypovolemia (low blood volume) resulting from inadequate resorption are the leading pathogenic effects of bacterial and viral gastroenteritis - The gastrointestinal tract contains an abundant bacterial flora = Various streptococci, including Streptococcus salivarius, inhabit the mouth, along with numerous spirochaetes and some strict anaerobes = The stomach and small intestine have relatively few bacteria, as the conditions that favor digestion (low pH, hydrolytic enzymes) do not favor growth of most microorganisms = The large intestine possesses an enormous native flora · Most of these are anaerobes, including species of Bacteroides, and are not readily isolated in the laboratory · The most common facultative anaerobe is Escherichia coli Dental caries (tooth decay) involve breakdown of enamal and dentin from teeth (Tortora et al., Figure 25.2)
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This note was uploaded on 11/24/2011 for the course BIO 113 taught by Professor Staff during the Fall '09 term at Rutgers.

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113lecture3506 - BIOLOGY 113 - MICROBIOLOGY Lecture 35:...

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