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Microbiology
Portals of Entry & Exit for Pathogens (Lecture 3)
| Question | Answer |
|---|---|
| 5 portals of entry & exit by which pathogens can enter & exit the body | 1. skin & mucous membranes 2. respiratory tract 3. digestive tract 4. genitourinary tract 5. placenta |
| Most frequently used portal of entry & exit by pathogens | respiratory tract |
| 2nd most frequently used portal of entry & exit by pathogens | digestive tract |
| Body's first good line of defense against entry of pathogens | unbroken skin |
| Abrasions, lesions and open wounds in the skin are an invitation to what? | disease-causing pathogens |
| The respiratory tract is often invaded by pathogens transmitted by what 2 types of transmission? | droplet & airborne transmission |
| Are droplet pathogens direct or indirect modes of transmission? | direct |
| Are airborne pathogens direct or indirect modes of transmission | indirect |
| Name a type of pathogen that can be inhaled in or exhaled from the body through the respiratory tract | pathogenic bacterial spores |
| Ingestion of contaminated food or water is a frequent cause of the spread of disease in the digestive tract of the body through what route? | oral-fecal route |
| Both sexually transmitted diseases (STDs) and diseases of the urinary system (UTIs)are spread between hosts through what tract? | genitourinary tract |
| Some pathogens are directly transmitted to the fetus through what? | placenta |
| Name the 9 vehicles of exit of pathogens | 1. feces 2. urine 3. semen 4. vaginal secretions 5. sputum 6. saliva 7. blood 8. pus 9. tears |
| The relative ability of the body to defend itself against infection is known as | resistance |
| The body is capable of limiting the occurrence of disease through what 3 types of defenses? | 1. mechanical defenses 2. physiological defenses 3. chemical defenses 2. |
| Nonspecific defenses of the host; first line of defense | 1. skin & mucous membranes 2. normal flora |
| Nonspecific defenses of the host; second line of defense | 1. phagocytosis 2. inflammation 3. fever 4. antimicrobial substances (interferons-chemical substances) |
| 4 Mechanical defenses against infection | 1. outer (epithelial) skin 2. normal flora 3. oils of the skin; salt in sweat 4. mucous membranes |
| The eyes possess a mechanical barrier to pathogens in what two forms? | tears and blinking |
| The respiratory tract is lined by hairs in the nasal passage, ciliated epithelium and muscous membranes which trap debris and sweep them toward the esophagus where they are swallowed. This mechanical defense is known as what? | ciliary escalator |
| The mechanical defense against infection in the urinary tract is accomplished through what? | flushing action of urine |
| 3 physiological defenses against infection | 1. inflammation 2. fever 3. phagocytosis |
| Inflammation is what type of physiological response to tissue damage? | local |
| 4 manifestations of inflammation | 1. calor (heat) 2. tumor (swelling) 3. dolor (pain) 4. rubor (redness) |
| Fever is what type of physiological response to infections? | systemic |
| Normal body temperature is what? | 37 degrees celcius 98.6 degrees fahrenheit |
| Phagocytosis; phagocytes (white blood cells) contain chemicals capable of breaking down what? | foreign cells and debris |
| 4 Chemical defenses against infection | 1. body secretions (fluids & mucous) containing antimicrobial chemicals 2.lysozymes - enzymes found in body fluids s 3. gastric juice - digestive cells that produce HCl (hydrochloric acid) 4.interferon (to inhibit the spread of viruses. |
| What is the chain of infection? | 1. causative agent (pathogenic organism) 2. reservoir for organism to survive (host) 3. port of exit for pathogen 4. pathogen transmitted to new host 5. pathogen enters new host via entry portal 6. new host becomes ill if conditions are right |
| 4 primary factors influencing the occurrence of disease | 1. virulence of the pathogen 2. portal of entry of the pathogen 3. number of pathogens present 4. resistance of the host |
| The relative power & degree of pathogenicity possessed by the organism to produce disease | virulence |
| The reduction of a microorganism's virulence by diluting or weakening its pathogenicity | attenuation |
| The sum total of body mechanisms that interpose barriers to the progress of invasions, multiplication of infectious agents or damage by their toxic products | resistence |
| Having little resistance to a disease or pathogen | susceptibility |
| Factors influencing the virulence of microorganisms | toxins |
| 2 types of toxins | endotoxins exotoxins |
| 3 types of exotoxins | 1. cytotoxins - kills hosts cells/affect function 2. neurotoxins- interfere with normal nerve impulses 3. enterotoxins- affect host cells lining the gastrointestinal tract |
| Characteristics of exotoxins | 1. generally a protein 2. produced by microorganism; excreted into surrounding medium 3. soluble in bodily fluids so they can easily diffuse into the blood and are rapidly transported throughout the body 4. heat labile (sensitive to the effects of hea |
| The body produces antibodiesthat provide immunity to exotoxins called what? | antitoxins (specific types of antibodies) |
| Characteristics of Endotoxins | 1. generally lipopolysaccharides 2. part of the outer portion of the cell wall of a gram negative bacteria; confined within the body of a bacterium that is freed only when the bacterium is broken down (lysis). 3. heat resistant |
| Are endotoxins exotoxins organic? | yes |
| What bacterial toxins target red blood cells? | hemolysins |
| Some microorganisms are more virulent due to their ability to produce enzymes that damage human tissue. Name some examples. | leukocidins hemolysins coagulase fibrinolysin (kinase) hyaluronidase lipase collagenase |
| Bacterial toxin that can destroy white blood cells that are very active in phagocytosis | leukocidins |
| Bacterial toxins that cause the lysis of red blood cells which are transporting oxygen to cells of the body | hemolysins |
| Bacterial enzyme that causes blood to clot | coagulase |
| Bacterial enzyme that prevents blood from clotting | fibronolysin (kinase) |
| Bacterial enzyme that breaks down hyaluronic acid (glue that helps hold connective tissue in the body; helps the microorganisms spread fro their initial site of infection. | hyaluronidase |
| Bacterial toxin that acts on the oils & fats secreted by the sebaceous glands | lipase |
| bacterial enzyme that breaks down the protein collagen fibers in connective tissue | collagenase |
| Virulent microorganisms | microorganisms capable of producing endospores, and contain a capsule or pili (fimbriae) |
| What part of a microorganism contains chemicals that contribute to its virulence? | cell wall |
| What bacteria has a large amount of waxes/lipids in the cell wall that makes the cell wall more resistant? | mycobacterium |
| Most prevalent white cells; phagocytes | leukocytes |
Created by:
karlbwilsonsr