What is a closed digestive system?

A closed digestive system is a type of digestive system in which the digestive tract is a continuous tube from the mouth to the anus, and food passes through it in one direction only. This means that there is no direct connection between the digestive system and the outside environment, except through the mouth and the anus.

The main advantage of a closed digestive system is that it helps to prevent the entry of harmful substances into the body. This is because food is only introduced into the system at one point (the mouth), and it cannot escape until it has passed through the entire digestive tract and been eliminated as waste.

In contrast, some animals have an open digestive system in which the digestive tract is not a continuous tube. Instead, it is open at one end, usually the anus, and food can enter and leave the system through this opening. This type of digestive system can be more efficient at extracting nutrients from food, but it also carries a higher risk of contamination with harmful substances.

Closed digestive systems are found in all vertebrates, as well as in some invertebrates, such as some molluscs and arthropods.