BIOL125_Ch14 Notes

BIOL125_Ch14 Notes - BIOL 125(Microbiology Text and Lecture...

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BIOL 125 (Microbiology) Text and Lecture Notes Chapter 14: Host Defenses 14.1. DEFENSE MECHANISMS OF THE HOST IN PERSPECTIVE a. Innate (Natural) Defenses – are present at birth, providing nonspecific resistance. b. Adaptive Immunities – are specific and must be acquired. i. First Line of Defense – any barrier that blocks invasion at the portal of entry. ii. Second Line of Defense – system of protective cells and fluid, which include inflammation and phagocytosis. iii. Third Line of Defense – high specific and adaptive; acquired as each foreign substance is encountered by lymphocytes. c. Barriers at the Portal of Entry: An Inborn First Line of Defense i. Lecture Notes. 1) In the eye, blinking and tear production flush out bacteria. 2) Digestive Tract. a) Saliva has lysozyme that breaks down peptidoglycan layer and kills bacteria. b) Mucous traps bacteria. c) Stomach acid kills bacteria. d) Defecation and vomiting remove bacteria and their toxins from the body. 3) Respiratory Tract. a) Nasal hairs trap larger particles and pathogens. b) Mucous production by the ciliated epithelium traps and flushes out the pathogens by sneezing or coughing. 4) Genitourinary Tract. a) Periodic emptying of the urinary bladder flushes out bacteria. b) Resident bacteria maintain a low pH, which prevents pathogens from surviving in the tract. ii. Physical or Anatomical Barriers at the Body’s Surface 1) Lecture Notes: Outermost layer of skin is composed of epithelial cells, impregnated with keratin. a) Action of the following prevents establishment of resident File: 26b250e67cb1cbba86238f2f889d2ae0cb4f2f2a.doc Updated 8/14/09
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Microbiology Text and Lecture Notes Chapter 14: Host Defenses Page 2 pathogens: i) Flushing effect of sweat glands removes pathogens. ii) Sebaceous gland secretions kills pathogens. iii) Dead skin cells are rapidly replaced, removing pathogens. iii. Nonspecific Chemical Defenses 1) Lysozyme – enzyme in tears that hydrolyzes the peptidoglycan in the cell wall of bacteria. 2) Dermicidin – antimicrobic peptide secreted by skin cells, which breaks down bacterial membranes and causes them to lyse. 3) Lecture Notes. a) Skin. i) Sebaceous secretions prevent bacteria from colonizing. ii) Sweat contains high lactic acid and electrolyte concentrations that kill bacteria. b) Internal Secretions. i) Hydrochloric acid in the stomach kills bacteria. ii) Digestive juices and bile of intestines destroys pathogens. iii) Semen contains antimicrobial chemical. iv) Vagina as an acidic pH. iv. Genetic Resistance to Infection 1) Lecture Notes. a) Some pathogens have a narrow range of specificity. i) Generally true for viral pathogens that require a specific receptor to bind to the host. b)
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This note was uploaded on 08/12/2009 for the course BIOL 125 taught by Professor Dr.sujathapamula during the Spring '09 term at San Jacinto.

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BIOL125_Ch14 Notes - BIOL 125(Microbiology Text and Lecture...

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