Introduction to the human digestive system?

If you mean the start of it well it is simply from the start due to eating food in need of necessary hunger

Introduction to the Digestive System. The digestive system includes the digestive tract and its accessory organs, which process food into molecules that can be absorbed and utilized by the cells of the body ... The salivary glands, liver, gallbladder, and pancreas are major accessory organs that have a role in digestion.