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Parasitology > 10. Nematodes intro > Flashcards

10. Nematodes intro Flashcards

1
Q

nematodes make up what fraction of the multicellular animals on earth?

A

4/5

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2
Q

how many species of nematodes have been described?

A

500,000

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3
Q

what is a non-parasitic nematode that is used for research and development?

A

Caenorhabditis elegans (C. elegans)

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4
Q

what is the most common human parasitic nematode worldwide?

A

Acaris lumbricoides

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5
Q

what is the most common human parasitic nematode in US/Canada?

A

Enterobius vermicularis

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6
Q

in most species _____ reproduction by adult nematodes is the norm and occurs within an infective definitive host

A

sexual

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7
Q

what are the ways in which the larval stages may be passed?

A
  • within the egg
  • free living in soil
  • parasitic in an intermediate host
  • parasitic in the definitive host
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8
Q

what is the basic life cycle of nematodes

A
  • egg
  • four larval stages (L1, L2, L3, and L4)
  • two adult stages comprising separate males and females
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9
Q

what is L5?

A

another name for sexually immature adults

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10
Q

what are the two phases of the life cycle of nematodes?

A
  • pre-parasitic

- parasitic

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11
Q

what stages are part of the pre-parasitic phase?

A
  • L1, L2 and L3

- the parasite must pass through these stages before the nematode is again infective for another host

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12
Q

what stages are part of the parasitic phase?

A
  • L3 and onward

- will undergo a migration within the body of the definitive host

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13
Q

which nematodes have infectious eggs?

A
  • ascaris (ex: ascaris lumbricoides)

- pinworm (ex: enterobius vermicularis)

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14
Q

which nematode is up to 30 cm in length and lives in the intestines of humans, horses, and pigs?

A

Ascaris

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15
Q

which nematode spends the entire lifecycle in or on the human host?

A

pinworm/Enterobius vermicularis

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16
Q

which parasite lays eggs in the perianal region causing itch?

A

pinworm/Enterobius vermicularis

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17
Q

which nematodes have infectious larvae?

A
  • adult hookworm (Necator americanus)

- trichina worm (Trichinella spiralis)

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18
Q

how do the larvae of the hookworm enter the human host?

A

by penetrating skin

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19
Q

describe the path in the body which is taken by the hookworm?

A

they penetrate the skin, enter the blood stream to travel to the lungs and are coughed up and swallowed in the sputum

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20
Q

what is the best way to avoid getting hookworm?

A

wearing shoes

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21
Q

what is the largest nematode and in what animal is it found?

A
  • Placentonema gigantisma
  • 9-13m long
  • found in sperm whales
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22
Q

is the body of a nematode segmented or non segmented? flat or round?

A
  • non-segmented

- round (roundworm) and tapered at both ends

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23
Q

what does the nematode body wall consist of?

A
  • an outermost cuticle

- an underlying hypodermis that secretes the cuticle

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24
Q

what is the cuticle made of?

A
  • the syncytial hypodermis secretes the thick outer layer of collagen
  • it is proteinaceous (not callagen) with outer lipid laters
25
Q

what are the characteristics of the collagenous cuticle?

A
  • tough

- flexible

26
Q

does a nematodes cuticle have cilia?

A

no

27
Q

how often is the cuticle molted/shed?

A

usually four times in the life of the nematode, as it goes through the life stages

28
Q

with which other groups does the nematode share the characteristics of a molted cuticle and the lack of cilia?

A
  • arthropods

- ecdysozoans

29
Q

what constrains the growth of the parasite between life stages?

A

the cuticle

30
Q

what are the two steps of molting?

A
  • SYNTHESIS of a new cuticle by the hypodermis
  • EXSHEATHMENT - a process by which the old cuticle is loosened and ruptured followed by the larva wriggling out of the casing
31
Q

what does exsheathment initiate?

A

infection

32
Q

the process of exsheathment during infection is not only _______ but is also _______ within the host

A
  • host-specific

- site-specific

33
Q

what kind of muscle lies below the hypodermis?

A

longitudinal muscle (NO circular muscle, meaning the worm cannot shorten and lengthen as do earthworms)

34
Q

movement of the parasite is due to _________ caused by contraction of the longitudinal muscles

A

undulating motion

35
Q

what type of motion is observed with longitudinal muscle?

A

dorsoventral flexion, which allows for the characteristic sinusoidal undulating motion

36
Q

what is another name for the body cavity?

A

pseudocoelom

37
Q

why is it a pseudocoelom and not a coelom?

A

it is not lined internally with cilia

38
Q

what fills the pseudocoelom?

A

pseudocoelomic fluid

39
Q

where are reproductive organs found?

A

suspended in the pseudocoelom

40
Q

what are the two functions of the pseudocoelomic fluid?

A
  • gives the body rigidity

- transports materials from cell to cell

41
Q

is the digestive tract complete or incomplete?

A

complete

42
Q

what are the parts of the digestive tract in order?

A

mouth –> pharynx –> oesophagus –> intestine –> anus

43
Q

what is found in the intestine to increase absorption?

A

microvilli

44
Q

who does most of the digestion, the host or the nematode?

A

the host, the nematode mostly just absorbed the digested food of the host

45
Q

what does the nervous system of the nematode consist of?

A
  • a ganglian nervous system
  • with an anterior neural ring,
  • and 2 or 4 longitudinal nerve truncs extending the length of the nematode
46
Q

what is another name for the anterial neural ring?

A

circumesophageal ring

47
Q

where is the excretory pore of the nematode?

A

near the mouth

48
Q

what are the characteristics of the excretory system?

A
  • simple and tubular
  • one or 2 one-celled renette glands and excretory ducts
  • excretory pore is anterior
  • NO flame cells*
49
Q

does the nematode have a respiratory system?

A

no

50
Q

how does gas exchange occur in nematode?

A

diffusion

51
Q

all nematodes are ______ (reproductive anatomy)

A

dioecious (separate male and female organisms)

52
Q

what does the reproductive system consist of?

A

tubular organs lying in the pseudocoelom

53
Q

what do all nematodes release?

A

eggs

54
Q

which are smaller, male or female nematodes?

A

male

55
Q

what is particular about the posterior end of a male nematode?

A

it is curved

56
Q

what does the male reproductive system consist of?

A

a single tubules starting with one testis and ending with a terminal cloaca and copulatory spicules

57
Q

what is different in the female reproductive system?

A

the organs are doubled

58
Q

what are the components of the female reproductive system?

A
  • 2 threadlike ovaries
  • 2 oviducts
  • 2 uterus
  • single genital pore at mid-body
59
Q

what is common about the male and female reproductive organs?

A

they are both tubular and continuous, and increase in diameter as they extend to the genital opening

Parasitology (27 decks)

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