BIOL123 - L10

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  • Created by: Katherine
  • Created on: 02-06-16 20:45
What are cestodes?
Tapeworms
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What are characteristic features of tapeworms?
Dorso ventrally flattened, ribbon like bodies - can be very long, scolex and strobili body plan, degeneration of non essential systems, body wall (tegument)
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How long are T.saginata?
4- 12m
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How long are T.solium?
4-8m
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How long are Echinococcus granulosus?
3 -6m
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What is the body plan of the cestodes?
Scolex and strobili (strobila = segmented part of tapeworm body - proglottids)
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What is degeneration of non essential systems?
Muscles, locomotory systems reguced and gut absent
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What is the body wall of the cestode like?
It is metabolically active through which nutrients are absorbed and secretions and waste materials exported.
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What are the chasracteristic features of cestodes?
Scolex, strobila, proglottids, strobilar growth,
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What is a scolex?
A small attachement organ that possesses hooks and sucks to attach to host tissues.
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What is the strobila?
A chain of proglottids - can grow 15 - 30cm a day
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What are proglottids?
They grow continuously from neck, new proglottids replace old
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What is strobilar growth?
When proglottids sequentially form from the neck behind the scolex.
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What are the types of tapeworms (Cestodes):
T.saginata - beef tapeworm, T.solium - pig tapeworm
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What are the features of T.saginata?
It has 4 large suckers - no sostellum and rostellar hooks
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What are the features of T.solium?
4 large suckers and rostellum containing double row of hooks. The scolex can be used to distinguish between tapeworm species.
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What are proglottids?
Each proglottid is minecious, caintaing both both male and female organs - testes and overies.
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Fertilisation can occur between proglottids of..
different tapewormds.
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After fertilisation, proglottids fill with eggs and...
The gravid proglottid breaks off and passes out in faeces of craw.
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How long are gravid proglottids?
T soilum - 7-13 uterine branches, T.saginata 15- 20 uterine branches.
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Where do tapeworms get their nutrition?
They absorb nutrients from host intestine directly via tegument. This is not a passive process and specialised membrane transport systems exist within the tegument.
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Microvillus projections do what?
Increase tegument surface area - similar to brush border on mammalian mucosal cells.
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How do the tapeworms excrete?
protenpheridium - functional unit of the excretory system. Also called flame cells (due to beating cilia looking like flickering flames) extend into a fine tubule. Cilia generate current excess water containing nitrogenous waste intotubule, out worm
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What does this excretion process allow for tapeworms?
It allows them to conserve water and elimitate salts - essential for survival in the host intestine.
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What are the only definitive host for T.saginate and T.solium
Humans
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Are T.saginate and T.solium eggs distinguishable?
No -
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How do the eggs remain in the environment for several weeks?
They have a thick membrane or wall - this forms a highly protective structure aroudn the internal oncosphere. The oncosphere burrows through muscose of the duodenum - passes into blood - encysts in tissue (cysticercus)
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How is transmission to the definitive host achieved?
Cysticerci - measly pork and beef - infective within 7- 10 weeks and remain viable for several months.
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What happens when the meat in ingested?
The cysteiceci excyst within the human intestine - scolex evaginated (activated by bile) and attaches to intesinal wall and develops into adult tapeworm.
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What is the geographical distribution of T.saginata?
Common in Africa
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What is the geographical distribution of T.solium
Worldwide distribution, rare where Muslims are
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What are the symptoms of tapeworms in humans?
Can cause intestinal blockages (segments become lodged in the appendix, bile or pancreatic ducts) or penetrate gut wall but pathology is usually inconsequential .
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Which tape worm shows more symptoms?
T.saginata because it is larger.
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What are the mild symptoms associated with adult tapewormd?
Digestive disturbances, abdominal pain, nausae and weight loss. The adults are long lived, 10-20 years
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Is meat okay to eat if it has cysicerci?
If there are a few, it can be frozen for at least 20 day and then is considered safe.
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If the entire carcus is destroyed then what must be done...
Meat must be thoroughly cooked to at least 56'C. Freezing is lethal to cysticerci, but it cen with stand 70 days at 0'C.
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Can humans be intermediate hosts for T.solium?
Yes
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What is cysticercosis?
Not aquired by eating undercooked pork, but by ingesting T.solium eggs excreted in human faeces. Cysts can form in the brain.
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How do you diagnose tapeowrms?
Identification of proglottids of T.solium in the faeces. In order to diagnose you must see cysts in tissue.
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How is it treated?
Praziquantel - it kills viable cysts, it can provoke an inflammatory response, making symptoms worse
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What is anothr cestode parasite
E.granulosus
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How long are the adult worms of E.granuloss?
3-6mm long.
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What is the lifecycle?
Adult in the intestine, the egg in the form of an oncosphere, theis is ingested by a human and becomes a hydatid cyst. The protoscolex formed by asexual reproduction causes the cyst to stay in place.
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What are characteristic features of tapeworms?

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Dorso ventrally flattened, ribbon like bodies - can be very long, scolex and strobili body plan, degeneration of non essential systems, body wall (tegument)

Card 3

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How long are T.saginata?

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Preview of the front of card 3

Card 4

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How long are T.solium?

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Card 5

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