Why are the salivary glands, pancreas , liver and gall bladder considered accessory glands of the digestive system?

The Salivary Glands, Pancreas, liver and gall bladder are considered to be accessory glands of the digestive system, since they are not really part of the digestive tract, but they play a role in digestive activities, that is why they are considered to be accessory glands. Their digestive activities may include providing energy and nutrients for the body.