Closed drains are tubes or other channel-like structures that are connected to a container, thereby creating a closed system. External drains go from inside the body to outside the body and can be seen, while internal drains are completely inside the body.
Conduits or channels that link to a container constitute closed drains, creating an enclosed system. In contrast, external drains originate internally and extend externally, becoming observable, while internal drains are completely contained within the body.