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Parasitology > Helminthes- Trematode Intro > Flashcards

Helminthes- Trematode Intro Flashcards

1
Q

What is the most common niche for helminthes in humans?

A

in the GI tract, as adults. They are one of the most prevalent forms of parasitic disease

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2
Q

By which two general means do helminthes do damage to the host?

A

through physical and chemical damage

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3
Q

What are the three groups of helminthes?

A

cestodes (tapeworms), trematodes (flukes), and nematodes (roundworms)

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4
Q

Which group of helminthes has proglottids that are each hemaphroditic?

A

cestodes

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5
Q

Which group of helminthes are all hemaphrodites with one exception?

A

all trematode species except schistosomes

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6
Q

Which group of helminthes are dioecious?

A

nematodes

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7
Q

Which groups’ bodies are covered by tegument?

A

cestodes and trematodes

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8
Q

Which group’s bodies are covered by cuticle?

A

nematodes

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9
Q

Which group lacks a digestive tubule?

A

cestodes

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10
Q

Which group’s digestive tubule ends in a cecum?

A

trematodes

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11
Q

Which group’s digestive tubule ends in an anus?

A

nematodes

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12
Q

How are digenetic trematodes classified?

A

by the organ that they invade

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13
Q

Where do blood flukes invade?

A

the vasculature of the GI or genitourinary systems

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14
Q

Where do intestinal flukes invade?

A

the lumen of the GIT

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15
Q

Where do live flukes invade?

A

the liver

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16
Q

Where do lung flukes invade?

A

lungs and sometimes other organs such as the CNS

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17
Q

What is a distinguishing feature of the trematode classification?

A

all trematodes are obligate parasites in all classes of vertebrates

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18
Q

What does digenetic mean?

A

the life cycle involves at least 2 hosts

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19
Q

What is the first intermediate host?

A

a mollusk, usually a snail

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20
Q

What is the definitive host?

A

a vertebrate

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21
Q

What is the name of the third host?

A

most trematodes have a second intermediate host

22
Q

Where do the larval stages most often occur?

A

in the intermediate host(s)

23
Q

Where do the adult stages most often occur?

A

in the definitive host

24
Q

Where is the oral sucker located and what is its function?

A

at the anterior end of the trematode and is used for attachment and feeding

25
Q

Define acetebulum

A

aka ventral sucker. located mid-ventral to oral sucker, has no internal opening, used for attachment only

26
Q

What is the syntegument?

A

the outer layer of the tegument body covering. contains mitochondria, secretory bodies and occasional spines. covered by a chemical layer

27
Q

What is cytotegument?

A

cells beneath syntegument that produce mucus. separated from syntegument by tegumental muscle and connected by cytoplasmic bridges

28
Q

What are the functions of the tegument?

A

1) osmoregulation & excretion
2) synthesis & secretion of mucus
3) absorption of nutrients

29
Q

Describe the trematode digestive tract

A

food enters mouth and passes into the esophagus, which separates into two long blind-ending cecum (no anus)

30
Q

Define parenchyma

A

loosely arranged cells filling space between internal organs

31
Q

What is the function of the excretory system?

A

removes excess water that has diffused into the worm

32
Q

What are flame cells and how do they function?

A

cells with beating flagella that create hydrostatic pressure to draw water from parenchyma into the collecting duct.
The collecting ducts empty into the excretory bladder at the posterior end

33
Q

Describe the nervous system of trematodes

A

Ladder-type system: anterior ganglion + lateral nerve trunks + connecting commissures. Sense organs in the tegument

34
Q

Which two ways can hermaphroditic trematodes reproduce?

A

via auto-fertilization OR require another worm for cross-fertilization (even though they are hermaphroditic)

35
Q

What are the components of the male reproductive system?

A

two testes -> sperm ducts (2 vas efferentia join to form vas deferens) -> cirrus sac

36
Q

What are the components of the female reproductive system?

A

SINGLE ovary produces eggs -> oviduct -> ootype

37
Q

Describe trematode eggs

A

well developed egg shells, usually operculate (having a lid) except in schistosomes (have spines)

38
Q

When and what happens when the egg hatches?

A

release of operculum.

can happen when ingested or under certain environmental conditions

39
Q

What distinguishing organ do most miracidium have?

A

cilia used for locomotion

40
Q

What do the miracidium do?

A

free-swimming stage that either seeks the intermediate host OR, in a few cases, is not free-swimming and hatches in the intestine to invade mollusk tissues

41
Q

What marks the transformation of the miracidium to mother sporocyst?

A

at the point of penetration where cilia, penetration glands and apical gland are lost

42
Q

What is the sporocyst cell and what does it become?

A

a hollow fluid filled germinal sac containing germ cells.

the germ cells either multiply & develop into daughter sporocysts or into a second larval stage (redia)

43
Q

How does the sporocyst obtain nutrients?

A

passage of soluble material across the tegument

44
Q

Can a trematode have both a daughter sporocyst and redia stage?

A

NO! if there is a daughter sporocyst stage, there is no redia stage and vise versa

45
Q

What are the distinguishing features of redia larvae?

A

more active form, has a simple gut (mouth + pharynx + simple intestine), may have a ridge-like collar

46
Q

What is the ridge-like collar?

A

located behind the mouth. Below this, the birth canal opens and either a daughter redia or cercariae emerges

47
Q

What can redia prey on?

A

sporocysts & redia of the same species or of other species

48
Q

Describe the cercarial stage

A

infective stage. variations in structure depending on species. usually free-swimming form.
Has a brief free-living stage. At this point may penetrate the next host or be ingested.

49
Q

What is the mesocercaria?

A

the stage where the cercaria enters a second intermediate host (3-host system)

50
Q

What is the metacercaria?

A

encysted form where the mesocercaria’s second intermediate host is ingested by a third intermediate host

51
Q

What are the potential final intermediate hosts?

A

a fish, an arthropod, another mollusc (usually an echinostome)

52
Q

How does the cercaria/metacercaria enter the definitive host?

A

can be ingested with the intermediate host by a carnivore definitive host OR ingested in encysted form when on plants by a herbivore definitive host

Parasitology (25 decks)

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