Cestodes

Question 1

What are cestodes?

Answer 1

Tapeworms

Question 2

Describe the general structure of a cestode

Answer 2

• head = scolex (contains suckers + hooks)
• neck
• body = strobila
• segments = proglottids (gradually maturing)
• covered by tegument
• microthrinx increase SA
• gravid segments drop off and contain eggs

Question 3

What are the 2 major groups of cestodes?

Answer 3

1. Pseudophyllidea - scolex with 4 longitudinal grooves

2. Cyclophyllidea - have 4 circular suckers around a scolex

Question 4

Describe the general lifecycle of a cestode

Answer 4

1. Adult tape worm passes a segment
2. Eggs are released and swallowed by an intermediate host
3. Larval tapeworm develops = metacestode
4. IH tissue eaten
5. Adult tapeworm develops

Question 5

Types of metacestode (tapeworm larvae): Cysticercus

Answer 5

Fluid filled bladder with 1 inverted scolex

Question 6

Types of metacestode (tapeworm larvae):

Cysticercoid

Answer 6

1 scolex with a fluid filled cyst wrapped around it (protection)

Question 7

Types of metacestode (tapeworm larvae):

Strabilocercus

Answer 7

1 scolex joined by numerous segments to a fluid filled cyst

Question 8

Types of metacestode (tapeworm larvae):

Caenurus

Answer 8

Like cysticercus but multiple inverted scolices

Question 9

Types of metacestode (tapeworm larvae):

Hydatid cyst

Answer 9

Like caenurus but thousands of inverted scolices

Question 10

Types of metacestode (tapeworm larvae):

Alveolar cyst

Answer 10

Like hydatid cyst by endogenous + exogenous budding