02. Helminths Flashcards
Parasitic helminths are always ____-parasites
Endoparasites
Why does harbouring a parasite affect the host?
Disrupts the nutrient uptake
Name mechanisms of survival that have evolved in parasitic helminths
immune evasion
immunological masking mechanisms
What are the ways that helminths injure their hosts?
- Mechanical means
- Chemical means
What is an example of a helminth that causes obstruction of the intestine?
- Ascaris lumbricoides
- Dog heartworm does a similar thing - blocks the heart
Name the categories of parasitic helminths
- Cestodes (Tapeworms)
- Trematodes (Flukes)
- Nematodes (Roundworms)
What is the shape of cestodes?
segmented and plane (flat)
Do cestodes have a body cavity?
NO
What is the body covering of a cestode?
Tegument (for absorption as well as classic functions)
Do cestodes have a digestive tube?
NO
Which parasitic helminths are hermaphrodites?
- Cestodes
- Trematodes (with the exception of Schisto, which are dioecious)
What category of parasitic helminth are Schistosomas?
Trematodes
What is the sexual morphology of Schistosomes?
Dioecious
What are the organs for attachment to the host in cestodes?
- Sucker (or bothridia)
- and some have a rostellum with hooks
What is the shape of trematodes?
Unsegmented and plane (flat)
Do trematodes have a body cavity?
NO
What is the body covering of a trematode?
Tegument
Do trematodes have a digestive tube?
Yes, but it is incomplete. it ends in the cecum (i.e. they have only an oral opening/not a complete gut)
What is the sexual morphology of trematodes?
Hermaphrotitic, except Schisto
What are the organs for attachment to the host in trematodes?
- Oral sucker
- Ventral sucker (acetalbulum)
What is the shape of nematodes?
Unsegmented, cylindrical (round)
Do nematodes have a body cavity?
YES
What is the body covering of a nematode?
Cuticle
Do nematodes have a digestive tube?
Yes, and it is complete - ends in anus.