lecture 4 Flashcards

1
Q

what are parasitic helminths?

A

parasitic worm-like organisms that live in and feed off living hosts

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2
Q

are helminths endoparasites or ectoparasites?

A

endoparasites

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3
Q

where do helminths live as sexually mature adults?

A

the GI tract

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4
Q

how do helminths injure their host? (2 ways)

A

mechanically and chemically

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5
Q

what are the three groups of helminths?

A
  • cestodes
  • trematodes
  • nematodes
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6
Q

for the _____, each proglottid segment of the adult tapeworm is hermaphroditic

A

cestodes

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7
Q

all _____ are hermaphrodites, except for the schistosomes

A

trematodes

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8
Q

adult parasitic _____ have separate male and female worms

A

nematodes

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9
Q

platyhelminths are flatworms because most are ________

A

dorsoventrally flattened

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10
Q

what are the two classes of Phylum Platyhelminthes?

A
  1. Class Cestoda - Tapeworms

2. Class Trematoda - Flukes

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11
Q

what are the two subclasses of class cestoda?

A
  1. subclass cestodaria

2. subclass eucestoda

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12
Q

what are the two orders of subclass eucestoda?

A
  1. order cyclophyllidea

2. order pseudophyllidea

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13
Q

cestodes lack a ____ & a _____

A

mouth & a digestive tract

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14
Q

what is the life cycle of a tapeworm?

A
the adult tapeworms live in the definitive host (predator) while the prey plays host to 
the intermediate stages.
o Eggs laid by the adult pass out 
in the feces of the definitive 
host and are eaten by the 
intermediate host.
o These develop into the 
intermediate stage, which 
generates the adult when 
eaten by the definitive host.
o A tapeworm may pass 
through several intermediate 
hosts before it finds the right  definitive host
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15
Q

what are the intermediate hosts of tapeworms?

A
  • a mammal
  • an arthropod
  • a fish
  • a bird
  • a reptile
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16
Q

what are the 3 distinct regions of a cestode?

A
  • scolex
  • neck
  • strobila
17
Q

what is a scolex?

A

the anterior point of attachment structure; a key feature in identifying the different tapeworms (NOT a mouth)

18
Q

whats the difference in the scolex structure between order cyclophyllidea and order pseudophyllidea?

A
  1. order cyclophyllidea - scolex contains 4 suckers and sometimes hooks
  2. order pseudophyllidea - scolex contains slit-like suckers or grooves called bothria
19
Q

what is the structure of the neck?

A
  • undifferentiated/unsegmented region between the scolex and the strobila
  • the narrowest part of the tapeworm
  • contain stem cells that are responsible for giving rise to new proglottids
20
Q

what is the structure of the strobila?

A

linear series of segments or proglottids

21
Q

what are the three types of proglottids?

A
  1. immature proglottids - newly formed
  2. mature proglottids - possess both male and female sex organs
  3. gravid proglottids - develop after mating; contain hundreds to thousand of embryonated eggs.

*each proglottid is an independently functioning unit

22
Q

which system develops first within the proglottid?

A

the male system

23
Q

the male organs disappear in ____ ____

A

gravid proglottids

24
Q

what are the structures of the female system?

A
  • ovaries (always 2)
  • vitelleria (yolk gland) - scattered or compact
  • mehlis’ gland
  • uterus (contains eggs in branches)
  • vagina (carries sperm to ootype)
  • common genital pore
25
Q

most of the female organs disappear in ___ ___, except for the _______

A

gravid proglottids

egg-filled uterus