4. Protozoa, Helminths, and Arthropods

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cornpops
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92497
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4. Protozoa, Helminths, and Arthropods
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2011-07-07 04:44:13
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PH162A midterm1
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public health microbiology lecture 4
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  1. protozoa
    • unicellular eukaryotic organisms
    • no cell wall
  2. protozoa nutrition
    • heterotrophic
    • some absorb soluble nutrients
    • others have specialized feeding structures - pseudopodia, cytosome
  3. pseudopodia
    • extension of cell cytoplasm
    • surround food source and engulf
  4. cytosome
    mouth-like structure surrounded by cilia, beating pulls food in
  5. protozoa digestion
    • occurs within food vacoules
    • unwanted byproducts excreted
  6. protozoa sensory and locomotion
    • some have rudimentary chemoreceptors
    • most are motile
    • structures related to locomotion:
    • - pseudopodia
    • - flagella
    • - cilia
    • - adhesive discs - prevent movement, used to attach
  7. protozoa protection
    • protect against drying, heat, chemicals, predators
    • usually only plasma membrane
    • some have:
    • pellicle - thin layer that supports plasma membrane
    • mineral shells
    • cysts - secretion of a thick outer layer, lowered metabolism resting, active form called trophozoite
    • trichocysts - intracellular organelles, thin threads shoot outward as defense mechanism, poison enemies
  8. protozoa reproduction
    • most species can reproduce:
    • asexually - new individuals are identical to parent
    • - binary fission
    • - schizogeny: multiple fission - survival advantage of massive infection
    • sexually - new individuals are genetically different
    • - syngamy: union of 2 dissimilar haploid cells
    • - conjugation: must have micronucleus and macronucleus, genernates genetic diversity, two way exchange
  9. protozoan classification
    • subphylum sarcodina
    • subphylum mastigophora
    • phlyum ciliophora
    • phlyum apicomplexa
  10. subphylum sarcodina
    • ameoba
    • move by pseudopodia
    • feed by engulfment
    • form cysts for protection
    • reproduction asexual by binary fission
  11. subphylum mastigophora
    • flagellates, move by flagella
    • absorb nutrients directly
    • form cysts
    • reproduction by binary fission
  12. phlyum ciliophora
    • cilliates, move by cilia
    • nutrients through cystostome
    • many have trichocysts
    • reproduction asexually by fission and sexuallly by conjugation
  13. phylum apicomplexa
    • nonmotile
    • absorb food directly
    • no special protection, live inside host
    • reproduce asexually by schizogeny, sexually by syngamy
  14. protozoa relevance
    • most are free-living in soil and water, do not relate to health and human disease, decomposers
    • commensal protozoa- flagellates and amoeba live in human mouth
  15. helminths
    • worms
    • microscopic
    • infective life stage is microscopic
    • cause human disease
  16. helminth life cycles
    • at least two forms = ovum, adult
    • most have 1 or two larval stages between
    • for parasitic, each phase may involve a different species of animal host -
    • definitive harbors the adult
    • intermediate hosts harbor larval phases
  17. helminth nutrition
    • heterotrophs
    • absorb directly or ingest through mouth
  18. helminth sensory
    • primitive nervous system
    • no brain but ganglia and nerve trunks
    • tactoreceptors and chemoreceptors
  19. helminth locomotion
    • some larval forms have cilia
    • muscle cells in larvae and adults
    • most parasitic have structure for attachment to tissue in host
  20. helminth protection
    • adult parasitic worms have thick skin to protect from fluids of host
    • ova have thick shells to protect from drying outside of host and against digestive juices
  21. helminth reproduction
    • some species dioecious- males and females separate
    • other hermaphroditic- male and female organs on same individual, self-fertilization is sexual
    • parthogenesis-asexual, unfertilized ova grows into new individuals
  22. helminth classification
    • phylum platyhelminthes
    • - class cestoida
    • - class tematoda
    • phylum nematoda
  23. cestodes (tapeworm)
    • head with suckers
    • primitive- no digestive system, absorbs nutrients through skim from the digestive tract of host
    • hermaphroditic
  24. trematodes (flukes)
    • suckers allow attachment
    • more advanced, digestive and excretory system
    • hermaphroditic, except schistosomes (dioecious)
  25. schistosomes
    • type of trematode that is dioecious
    • female lives in groove of male
  26. nematodes (roundworms)
    • cylindrical
    • more advanced, digestive system
    • most are dioecious, some can undergo parthenogenesis
  27. arthropods
    • advanced animals with well developed digestive, excretory, vascular, respiratory, and nervous systems
    • reproduction is sexual with separate sexes
    • hard exoskeleton made of chitin - like fungi
  28. insects vs. arachnids
    • insects:
    • 6 legs
    • head, thorax and abdomen
    • many have wings
    • flies, fleas, mosquitoes, lice, bugs

    • arachnids:
    • 8 legs
    • fused head and thorax (cephalothorax)
    • no wings
    • spiders, ticks, mites
  29. arthropods relevance
    • vectors - transmit microorganisms
    • allergies - dust mites live in dust, excretions of dust mites cause allergy
    • ectoparasites - live on exterior of human skin

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