Accessory Organs of Digestion-Part One
of the digestive system are those that help in digestion but are not a direct part of digestive tract.
Salivary glands, pancreas, liver and gallbladder
are the accessory organs of digestion.
The glands that produce saliva in mouth are called salivary glands. There are three major pairs of salivary glands: parotid, submandibular and sublingual. These pairs are situated in either side of the head. Parotid glands are located in front of both ears. Submandibular salivary glands are under the mandible or the lower jaw. Sublingual salivary glands are under the tongue.
The main function of the salivary glands is to produce saliva. This is done by two types of cells in the glands:
The serous cells produce a watery fluid that is rich in amylase. The main function of amylase is the break starch and glycerol into complex sugars. The mucous cells secrete mucus. Mucus us thick and sticky liquid. This sticky liquid binds the food and acts as lubricator while swallowing. The combination amylase and mucus is called saliva. Linings of mouth also contains mucus secreting cells that will enhance the swallowing of food in mouth.
The pancreas is a elongated gland that lies posterior to the stomach. Pancreas has two functions: As an endocrine gland it secrets hormones like insulin and as an organ of digestive system it produces digestive juices.
The digestive portion of the pancreas produces digestive juices such as amylase, lipase and proteinase. Amylase acts to break down carbohydrates, proteinase breaks proteins and lipase acts to break fats into simpler compounds. These juices are secreted through the pancreatic duct to the duodenum. This duct is called common bile duct. The endocrine portion of the pancreas are cellular islands called islets of Langerhans that are embedded in pancreas exocrine units. Thus pancreas is known as a compound gland.