Mechanisms of Disease

1. Mechanisms of Disease Disturbances to homeostasis and the body’s responses

2. Disease Mechanisms • Genetic mutations • Pathogenic organisms and particles • parasites • Tumors and cancer • Physical and chemical agents • Malnutrition • Autoimmunity • Inflammation • Degeneration

3. Risk Factors • Genetic factors • Age • Lifestyle • Stress • Environmental factors • Preexisting conditions Many risk factors overlap and can be avoided.

4. Pathogenic particles • Viruses – • small,nonliving particle, • capsid and nucleic acid • can not reproduce on own • Symptoms can be slow to appear • Ex. SARS, West Nile, HIV (table 5-1) • Prion – pathogenic protein molecule, convert normal proteins to abnormal ex. Mad cow

5. Bacteria- Pathogenic organism • Prokaryotic • Produce disease by: • secreting toxins • parasitic in human cells • form colonies to disrupt normal function • Classified by • Function: aerobic/anaerobic • Staining properties: gram -, gram + • Size and shape – coccus, spirilla, bacillus • Table 5-2 for examples Spores – formed under adverse conditions

6. Fungus • Fungus • Heterotrophic, parasitic • Molds, mildew • Often resists treatment • Ex. Athelete’s foot, yeast infections (table 5-3)

7. Protozoa • Unicellular, eukaryotic organisms • Larger than bacteria • Major groups (classified by locomotion) • Amoebas • Flagellates • Ciliates • Sporozoa (usually 2 hosts and 2 life cycles) Table 5-4 for examples

8. Pathogenic Animals - metazoa • Large, multicellular • Major groups • Nematodes – roundworms, human tissue • Platyhelminths – flatworms and flukes • Arthropods – mites, ticks, lice and fleas, wasps, mosquitoes, spiders • Table 5-5 for examples