Final answer:
Glands that lie outside the GI tract and send their contents into it by means of ducts are located in the salivary glands, liver, pancreas, and gallbladder. These are known as accessory organs and include exocrine glands that secrete substances vital for digestion.
Step-by-step explanation:
The glands that lie outside the GI tract and send their contents into the GI lumen by means of ducts are located in several accessory organs. These organs secrete or store substances needed for digestion and are not part of the direct passage of food through the GI tract. The salivary glands, for example, deliver saliva into the mouth through ducts, aiding in the chemical digestion of food. Furthermore, the liver, pancreas, and gallbladder are other key accessory organs involved in this process. The liver and pancreas among these produce vital enzymes and substances such as bile that are carried to the GI tract to aid in the breakdown of food.
These organs are considered exocrine glands because they release their secretions through ducts that lead to the epithelial surface. These secretions, including enzymes and bile, are essential for the digestion of nutrients. Without the proper functioning of these accessory organs, many significant diseases can arise due to their malfunction.