Nematoda Flashcards
what newly classified group does nematodes belong to and why
Ecdysozoa
Three layer cuticle and they molt when they grow (ecdysis)
Nematodes are the first group that can be terrestrial. They are also parasitic. Where are they very abundant in?
soil
What do nematodes possess that flatworms dont ?
Body cavity
between single mesodermal layer and endoderm.Called pseudocoelom
Full of liquid and the pressure supports muscle; hydrostatic skeleton
Why doesnt nematodes need scolex for attachment?
They are MOTILE so they dont need to attach to small intestine to move.
They use peristalsis from oesophagus action to force them down
Structure of nematodes
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
Are nematodes protosomes or deuterosomes
Protosomes
Difference between protosomes and deuterosomes
protosomes: blastophere becomes mouth first then anus develops
deuterosomes: blastophere becomes anus then mouth develops
humans are deuterosomes
what are soil transmitted nematodes called
geohelminths
adult geohelminths are anaerobic but larval stage aerobic
intestinal paarasites
infection through fecal contamination of soil or food, water
no intermediate host
Ascaris lumbricoides are the largest intestinal nematodes. What size can they get to
female: 40cm
male:15-30cm
Why is the nematode Ascaris lumbricoides important
most common human helminthic infection
can be spread in europe
*this and eccinhoccus granulosas endemic to this region
diagnostic stage of ascariasis
eggs in faeces
Life cycle Ascaris lumbricoides
- 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
Name some geohelminths
Ascaris lumbricoides
Trichiurus trichiura (whipworm)
Strongyloides stercoralis
Ancylostoma duodenale (hookworm)
Enterobius vernicularis (pinworm)
Why cant you cant get autoinfection from Ascaris lumbricoides
after ingestion of eggs, 2-3 months required for new egg production
Life cycle of Trichiurus trichiura (whipworm)
- 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
2 stages of Strongyloides stercoralis in its life cycle
parasitic stage in human
free living stages in soil
Life cycle of Strongyloides stercoralis
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
which nematode is the old world hookworm
Ancylostoma duodenale
How big are the males and the females in A.duodenale
fem: 13 mm
male:11mm
whats the infective stage of S.stercoralis
larvae passed in stoop
NOT EGG IN FAECES
life cycle of Ancylostoma duodenale (anaemia)
- 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
what can hookworms cause in children in the tropics
chronic anemia and stunts growth
How large are Enterobius vernicularis (pinworm)
fem:13mm
male: 5mm
Can E.vernicularis cause autoinfection
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