Platyhelminthes

Definition

Platyhelminthes, also known as flatworms, are a phylum of simple bilaterian, unsegmented, soft-bodied invertebrates. Many platyhelminths are parasitic and can infect various hosts, including humans.

5 Must Know Facts For Your Next Test

1. Platyhelminthes include major parasitic groups such as tapeworms (Cestoda) and flukes (Trematoda).
2. Flatworms lack specialized respiratory and circulatory systems; they rely on diffusion for gas exchange.
3. They have a simple digestive system with only one opening that serves as both mouth and anus.
4. Some platyhelminths exhibit remarkable regenerative capabilities and can reproduce both sexually and asexually.
5. Schistosomiasis is a significant disease caused by trematodes that affects millions of people worldwide.

Review Questions

• What are the two major parasitic groups within the Platyhelminthes phylum?
• How do Platyhelminthes perform gas exchange given their lack of specialized respiratory systems?
• Describe the digestive system of Platyhelminthes.

Related terms

Cestoda: A class within Platyhelminthes known as tapeworms, which are intestinal parasites.

Trematoda: A class within Platyhelminthes comprising flukes, which often infect the liver or blood vessels of hosts.

Schistosomiasis: A disease caused by infection with freshwater parasitic worms in the Trematoda class.