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Biology > Nematoda > Flashcards

Nematoda Flashcards

1
Q

what newly classified group does nematodes belong to and why

A

Ecdysozoa
Three layer cuticle and they molt when they grow (ecdysis)

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2
Q

Nematodes are the first group that can be terrestrial. They are also parasitic. Where are they very abundant in?

A

soil

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3
Q

What do nematodes possess that flatworms dont ?

A

Body cavity

between single mesodermal layer and endoderm.Called pseudocoelom

Full of liquid and the pressure supports muscle; hydrostatic skeleton

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4
Q

Why doesnt nematodes need scolex for attachment?

A

They are MOTILE so they dont need to attach to small intestine to move.
They use peristalsis from oesophagus action to force them down

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5
Q

Structure of nematodes

A

lips=touch and sense

acellular cuticle layer

2 openings of digestive tract: mouth and anus

Excretory system – two lateral ducts that run longitudinally down either side of the body

Nervous system: dorsal and ventral nerve cords

No circulation or respiratory system so no filtration of blood

Separate sexes: fem bigger than male. Male has coiled posterior end

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6
Q

Are nematodes protosomes or deuterosomes

A

Protosomes

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7
Q

Difference between protosomes and deuterosomes

A

protosomes: blastophere becomes mouth first then anus develops

deuterosomes: blastophere becomes anus then mouth develops

humans are deuterosomes

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8
Q

what are soil transmitted nematodes called

A

geohelminths

adult geohelminths are anaerobic but larval stage aerobic

intestinal paarasites
infection through fecal contamination of soil or food, water
no intermediate host

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9
Q

Ascaris lumbricoides are the largest intestinal nematodes. What size can they get to

A

female: 40cm
male:15-30cm

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10
Q

Why is the nematode Ascaris lumbricoides important

A

most common human helminthic infection

can be spread in europe
*this and eccinhoccus granulosas endemic to this region

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11
Q

diagnostic stage of ascariasis

A

eggs in faeces

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12
Q

Life cycle Ascaris lumbricoides

A
  • eggs released in faeces
  • larvae forms in soil. Another host injests eggs
  • larave hatches in small intestine but it needs oxygen
  • It goes to lungs and grows there
  • Goes along bronchial tree to oesophagus and is swallowed
  • develops into adult worm in small intestine
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13
Q

Name some geohelminths

A

Ascaris lumbricoides
Trichiurus trichiura (whipworm)
Strongyloides stercoralis
Ancylostoma duodenale (hookworm)
Enterobius vernicularis (pinworm)

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14
Q

Why cant you cant get autoinfection from Ascaris lumbricoides

A

after ingestion of eggs, 2-3 months required for new egg production

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15
Q

Life cycle of Trichiurus trichiura (whipworm)

A
  • eggs shed from human faeces to soil
  • eggs become embryonated after 2-3 weeks
  • Human injests eggs and hatch in small intestine (growth and molting here) Infective larvae penetrate villi
  • Young worms penetrate the mucosa of cecum (large int) Develops into worms
  • injestion to maturity=3 months

NO AUTOINFECTION

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16
Q

2 stages of Strongyloides stercoralis in its life cycle

A

parasitic stage in human
free living stages in soil

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17
Q

Life cycle of Strongyloides stercoralis

A

FREE LIVING:
* Rhabditiform larvae in the intestine are excreted in stool

  • Develops into free living adult worms (male and fem)
  • eggs are produced by fertilized female worms. Rhabdidiform larvae hatch
  • Rhabditiform develop into filariform

PARASITIC:
* If infective filariform larvae penetrate skin, it migrates to small intestine to become adults

  • Develops into parasitic FEMALE worms. Lays eggs in intestinal mucosa

*Rhabdidtiform larvae hatch and migrate to intestinal lumen

AUTOINFECTION: rhabditiform in large intestine become filariform, penetrate intestinal mucosa + migrate

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18
Q

which nematode is the old world hookworm

A

Ancylostoma duodenale

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19
Q

How big are the males and the females in A.duodenale

A

fem: 13 mm
male:11mm

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20
Q

whats the infective stage of S.stercoralis

A

larvae passed in stoop
NOT EGG IN FAECES

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21
Q

life cycle of Ancylostoma duodenale (anaemia)

A
  • eggs passed in poo, Rhabditform larvae hatch
  • they grow in feces/soil and develop into infective filariform larvae

*Penetrates skin, carried through blood vessels

  • Ascend bronchial tree and pharynx then swallowed
  • larvae matures in small intestine
  • attach to intestinal wall sucks blood, caises ANEMIA
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22
Q

what can hookworms cause in children in the tropics

A

chronic anemia and stunts growth

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23
Q

How large are Enterobius vernicularis (pinworm)

A

fem:13mm
male: 5mm

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24
Q

Can E.vernicularis cause autoinfection

A

yes because they are small and can lay eggs outside the body (around anus) can eat them from hands.
Also eggs injested from contaminated surfaces

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25
Q

Life cycle of Enterobius vernicularis

A
  • Eggs deposited on perianal folds
  • infection occurs by transferring infected eggs into mouth
  • Larvae hatches in small intestine
  • adults develop in the colon
  • Gravid females migrate outside of anus at NIGHT and lay eggs
  • larvae develop in 4-6 hours
26
Q

how do female E. vernivularis lay their eggs

A

Produces GLUE to adhere the eggs around anus

27
Q

What is the diagnostic and infective stage of E.vernicularis

A

Both the same

Eggs

BUT NOT IN FAECES ITS AROUND ANUS

28
Q

which region is E.vernicularis most common

A

high sanitation areas

29
Q

name the non geohelminth nematodes and which ones are filarian (transmitted by blood sucking insects)/ tissue ( not by insects)

A

T. trichinella spiralis
T. dracunculus medinesis
F. wuchereria bancrofti
F. loa loa
F. onchocera volvulus

30
Q

Trichinella spiralis length and infective stage

A

F= 2mm m= 1mm
infective = larve NO EGGS

31
Q

Trichinella spiralis life cycle

A
  • Ingesting undercooked meat with encysting larvae
  • larvae released from cysts + invade intestinal mucosa + develop into worms
  • females release larvae that move to straited muscle and encyst.
  • adult worms and larvae develop in the same host so new host is needed to start a new cycle. resovoir hosts = rodents
32
Q

what does the larvae do in Trichinella spiralis

A

modifies areas of skeletal muscle cells and turn them into nurse cells

33
Q

Dracunculus medinesis (guinea worm) length and infective stage

A

f = 80cm m= 4cm
infective stage = copepods (int host) + larvae

34
Q

Dracunculus medinesis life cycle

A
  • Humans infected by drinking water with copepods infected with larvae/ eating fish with the infected copepods
  • larvae penetrates the hosts stomach + intestinal wall
  • after developing to adults and copulation, male worms die
  • females migrate towards skin surface
  • 1 year after maturation, the f worms makes blister on skin (foot)
  • Blister ruptures when contact with water, worm emerges + release larvae
  • if ingested by copepod, later it develops into infective larvae
35
Q

how to cure Dracunculus medinesis

A

no vaccine for dracunculiasis but filtering h20 is a prevention

36
Q

Wuchereria bancrofti (thread like worm) length

A

f = 10cm m= 4cm

37
Q

Wuchereria bancrofti infective stage and int host

A

int host = culex mosquito
infective stage = larvae

38
Q

Wuchereria bancrofti life cycle (mosqs)

A
  • During blood meal, infected mosquito introduces filarial larvae onto human skin
  • larvae penetrates wound + develops into aadult and live in lymphatics
  • they produce microfilariae + they migrate into lymph + blood channels.
  • daytime - larvae live in deep seated blood vessels
    nighttime - they migrate to peripheral blood vessels ( to be
    available for mosqs)
  • fem mosqs ingest microfilariae after biting
  • microfilariae develop to 1st stage larvae then 3rd stage infective

** parasite DOESNT MULTIPLY in mosquito

39
Q

what disease does Wuchereria bancrofti cause and its symptoms

A

Lymphatic filariasis (elephatiasis)
develop swollen legs/arms

40
Q

Loa Loa (eye worm) length

A

f= 70mm m= 34mm

41
Q

Loa Loa int host and infective stage

A

int host = deer fly (chrysops)
infective = microfilariae/filarial larvae

42
Q

Loa Loa life cycle (deerfly)

A
  • female births living microfilariae inside skin
  • microfilariae travels in blood during the day, nighttime they live in the lungs
  • When deerfly takes blood meal from infected human, it ingests microfilariae
  • mf lose their sheaths + develop into 1st then 3rd stage filarial larvae.
  • larvae invades another person during next blood meal
  • 3rd stage larvae transferred from flys mouth to human skin. burrows into wound + enters subcutaneous layer and matures
43
Q

Onchocera volvulus length

A

f = 5cm m = 3cm

44
Q

Onchocera volvulus int host and infective stage

A

int host = Blackfly
infective stage = filarial larvae

45
Q

Onchocera volvulus life cycle

A
  • Blackfly takes blood meal + introduces 3rd stage larvae to skin. they penetrate wound
  • in subcutaneous tissues, larvae develops to adult microfilariae
  • lives in connective tissues (up to 15 years)
  • Blackfly ingests microfilariae during another meal
  • Develops to 1st then 3rd stage infective larvae + can infect another person
46
Q

What is condition called if human is accidental host of foreign nematode (non human nematode)

A

Larva Migrans
Cutaneous or visceral

47
Q

What is cutaneous migration

A

Humans acquire filariform through penetration of skin

migration to human connective tissue but larvae cannot become adults worms therefore die

48
Q

What is visceral migrating larva?

A

human swallow eggs of foreign nematode

migrate to small intestine and die in liver/lung

Example: Toxocara canis

49
Q

Nematodes are often species specific, which nematode is non species specific

A

Trichinella spiralis

50
Q

How can humans acquire the parasite trichinella spiralis

A

cycle is completed in 1 host

Can only get parasite if you eat raw infected meat of previous host

humans kind of dead end for parasite as nothing really eats humans

51
Q

Trichinella spiralis realeses what in small intestine if female already releaes eggs in uterus?

A

larvae

52
Q

Which parasite known as guinea worm

A

Dracunculus medinenis

53
Q

which is the longest nematode ever

A

Dracunculus medinenis

fem: 120cm
male: 4cm

54
Q

how does primary host (human) acquire Dracunculus medinenis

A

drink contaminated water with copepods

55
Q

How does the Dracunculus come out

A

female needs to liberate larva

comes out from foot by blister after a year

56
Q

What condition does Wuchereria bancrofti cause

A

Elephantiasis (swollen leg)

57
Q

Why does Wuchereria bancrofti cause swelling

A

adult worms die in lymph nodes

causes blockage of lymphatic system

58
Q

what is the swelling called when Loa loa migrates to subcutaneous layer

A

Calbar swelling

59
Q

what is the difference between pseudocoelom and coelom

A

pseudo: between mesoderm and endoderm layers

coelom: 2 mesoderm layers

60
Q

Structure of adult and egg of Trichocephalus trichiurus

A

adult: fem bigger and longer than male. male has coiled end. 2 openings of mouth and anus, excretory and nervous system, pseudcoelom

egg: lemon shaped

Biology (36 decks)

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