Accessory Organs of Digestion
The alimentary canal or the human gastrointestinal tract refers to the stomach and the intestines. Strictly speaking, the digestive system essentially is made up of these two tubular structures. However, human digestion cannot be completed in these two structures. There are certain
accessory organs of digestion
which play a key role in the process. Hence, they are more than mere accessories to digestion.
The accessory digestive organs are as follows:
- Salivary Glands
Teeth and Tongue are not as such and hence often not classified in the said category. The tongue is a muscle and the teeth are bones. Never the less, they are the starting point of the digestive process. The teeth help to break down the food into smaller pieces. The tongue induces taste and helps to mix the food with saliva and is useful in the transit of the food from the mouth to the stomach through the esophagus.
In this article, we are going to provide a brief explanation of each organ from the list of the
accessory organs of digestion
and the diseases affecting them.
: The salivary glands are ductile glands that are present in the mouth. Salivary glands consist of two types of secretory cells. First, would be the serous cells that secrete the digestive enzyme amylase and the second would be the mucus cells which secrete the thick slimy fluid mucus. These two fluids act on the food in the mouth helping it to be broken down and passed on to the stomach. The enzyme amylase helps to break down starch into maltose. Saliva is secreted by the serous and the mucus cells in the salivary glands. One liter of saliva is secreted from these glands every day.
- The most common disease to affect the salivary glands is salivary duct calculus, which is the formation of calcified deposits or stones in the salivary glands. This hampers the production of saliva.
- Tumors of the salivary glands can also affect them adversely.
- Anti cancer treatment involving radiation, chemotherapy etc. can also severely affect the glands.
Pancreas is an elongated gland lying posterior to the stomach. It serves both as an endocrine organ secreting important hormones like insulin, glucagon and somatostatin and also acts as a digestive organ as it secretes enzymes such as amylase, protease and lipase which help to break down the proteins, fats and carbohydrates present in food. It releases these enzymes through the pancreatic duct into the common biliary duct which carries it to the small intestine along with the bile.
- The most common pancreas related disease is Type 1 Diabetes. It is an auto immune disorder in which the immune system starts attacking the insulin secreting cells of the pancreas and affects its secretion.
- Acute pancreatitis refers to an intense inflammation and infection of the organ caused by alcoholism or gallstones. The gallstones could travel down from the gallbladder and get lodged in the pancreatic duct. The retention of the pancreatic enzymes in the organ starts destroying the cells of the pancreas itself. This is known as autolysis or self digestion and damages the pancreatic tissue permanently.
- Pancreatic cancers or the formation of malignant tumors in the organ is a disease with extremely high mortality rate.
Liver is the largest gland and is situated in the right side of upper abdomen, just below the diaphragm and superior to pylorous and duodenum. It is an extremely important organ with a wide range of functions which are as follows:
- It produces bile which is an alkaline compound which helps in digestion, especially fats.
- Carbohydrates, proteins and fats are metabolized and absorbed.
- It detoxifies byproducts of protein digestion and other chemicals found in medications and drugs taken.
- It helps to break down or decompose red blood cells. Bilirubin is a byproduct of this metabolic process. It is excreted in bile and urine.
- It produces coagulation factors that help in clotting of blood.
- Glycogen obtained from carbohydrates and stored in the muscles is converted into Adenotriphosphate to be used as energy.
- It stores Vitamin A, D, B12 and iron.
- The most common liver diseases are infections as in Hepatitis A, B, C and E. These are essentially viral infections caused by the Hepatitis A, B, C or E virus. It is infectious and spreads from coming in touch or consuming any item contaminated with the virus.
- Alcohol damage or liver cirrhosis is a disease which involves destruction and permanent damage of liver tissue from excess alcohol consumption.
- Fatty liver or the inability of the liver to metabolize excess amount of fats in diet and leading to the deposition of it in the cells of the liver tissue.
- Drug induced liver injury is another common disease which is caused from toxins derived from the metabolism of certain drugs like acetaminophen in certain individuals.
- Cancers in the liver are also common with very high mortality rates.
It is a pear shaped sac located below the liver. The main function of the gallbladder is to store and concentrate bile obtained from the liver and release it to the duodenum or the small intestine as and when it is stimulated by fats. The neck of the organ tapers into a narrow duct known as the cystic duct. The cystic duct merges in to the common bile duct. The pancreatic duct also merges in it and finally it gets connected to the duodenum.
The most common disease of the gallbladder is caused by gallstones. Gallstones are formed from emulsified fats, cholesterol, bile salts etc. They can travel down and get lodged in the neck of the organ or in any duct carrying bile towards the duodenum. The bile retention caused by it leads to inflammation and infection as in acute gallbladder disease. Other conditions like ascending cholangitis, gallstone ileus, perforated gallbladder etc. are complications of gallbladder infection.