In Platyhelminthes, what structure serves as the digestive system?

• A. Gastrovascular cavity
• B. Alimentary canal
• C. Crop and gizzard
• D. Digestive glands

Answer: (A)

Platyhelminthes rely on a gastrovascular cavity to digest and distribute nutrients. This is a sac-like cavity with a single opening that serves as the mouth; there is no separate anus or through-gut. Digestive enzymes act in the cavity to break down food, and nutrients are taken up by cells lining the cavity. This simple system contrasts with an alimentary canal, which is a complete digestive tract with two openings. Digestive glands or specialized structures like a crop or gizzard aren’t the main digestive organ in these flatworms. So, the digestive system is the gastrovascular cavity.