FLATWORMS

1
FLATWORMS

• Phylum Platyhelminthes

2
Phylum Platyhelminthes

• Three germ layers
• Epidermis derived from ectoderm
• Mesoderm
• Gastrodermis (gut lining) derived from endoderm

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Platyhelminthes

• Acoelomate
• No cavity within mesoderm

4
Platyhelminthes

• Sac plan body
• One opening to gut serves as mouth and anus
• Time partitioning of gut function
• Intracellular digestion
• Branched gut

5
Platyhelminthes

• Muscular pharynx
• Usually retracted into sheath
• May be protruded, extended to ingest food

6
Platyhelminthes

• Simplest ( earliest ?) animals that are
• Motile, move through their environment
• Bilaterally symmetrical, streamlined to reduce
  friction, drag
• Cephalized, have concentration of nervous tissue
  (brain) and sense organs at leading end.

7
Platyhelminthes

• Phylum Platyhelminthes
• Class Planarians
• Class Flukes
• Class Tapeworms

8
Platyhelminthes

• Phylum Platyhelminthes
• Class Flukes
• Parasites
• Anterior mouth
• Oral sucker

9
Platyhelminthes

• Phylum Platyhelminthes
• Class Tapeworms
• parasites
• Scolex proglottids
• No gut (absorb nutrient molecules across skin)