ANATOMY AND PHYSIOLOGY OF ACCESSORY DIGESTIVE ORGANS
An accessory organ of the digestive system is the salivary glands. They are in pairs and include the parotid,
mandibular, and sublingual salivary glands. The parotid glands are located under the ears of animals. Their ducts
pass over the rear of the mandible to near the middle of the cheek. Here, the ducts penetrate the mucous membrane
of the mouth and secrete saliva. The mandibular salivary glands are under and to the rear of the parotid glands.
Their ducts pass in the middle of the mandibles and open into the mouth under the tongue. The sublingual salivary
glands are located under the mucous membrane around the outer sides of the tongue. They empty into the floor of
the mouth.
According to the type of fluid they secrete, the salivary glands are classified as serous, mucous, or mixed. The
serous type secretes a clear, watery fluid. The mucous type secretes a thick, cloudy substance. This substance
serves as a protective coating to the mucous membranes of the digestive system. Mixed salivary glands secrete
body mucous and serous fluids. The parotid and mandibular salivary glands secrete only the serous type of fluid.
The sublingual salivary glands secrete mixed fluids. They are not as well defined as the other two types of
salivary glands.
The pancreas is an elongated, somewhat lobe-shaped organ. It is located close to the beginning of the small
intestine and behind the liver. It has both exocrine and endocrine functions. The exocrine part is the largest and
produces digestive juices. These juices pass through the pancreatic duct and then empty into the beginning of the
small intestine or duodenum. The endocrine part of the pancreas produces the hormone insulin. Insulin goes directly
into the bloodstream.