Parotid glands are a pair of the major salivary glands, and the largest ones. They produce and release saliva into the mouth to help chewing and swallowing foods. Each one is located on either side of the mouth, behind the last upper molar teeth, and in front of the ears. They produce 20 % of the total saliva that is present in the mouth.
Each parotid gland is wrapped around the mandibular ramus of the mandible, which is the back perpendicular extremity of the mandible bone on either side. The saliva produced is secreted through the parotid duct (also called Stensen duct), of which the exit is located near the second upper molar.
In the mouth there are three major salivary glands, each present in pairs: parotid glands, submandibular glands, and sublingual glands. There are also hundreds of minor salivary glands which are located all over the mouth. The saliva that is produced by all these glands can be either serous (watery fluid) or mucous (thick and viscous fluid). Parotid glands are the largest of the major salivary glands and they secrete serous type of saliva, which means that it contains the enzymes that break down carbohydrates into glucose and maltose.
Functions of the parotid glands
The main function of the parotid glands, and all other glands, is initiating digestion. Enzymes contained in saliva such as amylase, break down foods. Mucus that is secreted from other salivary glands, lubricates the food preparing amylase to do its work. This process will transform food into a small round and slurry build-up called a bolus, which will make its way to the stomach.
Saliva also protects the teeth because they are lubricated with the mucus produced by the other salivary glands . Saliva also has enzymes that break down bacteria contained in dental plaque that normally initiates cavities and gum disease.
Saliva produced by the parotid gland and other salivary glands, also help in the processes of tasting foods and cleaning the mouth after a meal.
Disorders of the parotid gland
Xerostomia can affect all salivary glands, and it is expressed by a production of a lesser quantity of saliva in the mouth. This can follow many diseases, such as diabetes, and it can also be a side effect of several drugs. Xerostomia can increase the risk of having dental cavities.
Hypersalivation is the opposite where a lot of saliva is produced. This can be a side effect of a few diseases, the use of a few drugs, or exposure to substances such as copper, mercury or arsenic.
Mumps is the swelling of parotid glands following a viral infection (Mumps orthorubulavirus). It is highly contagious and can spread by airborne droplets from salivary, nasal and urinary secretions. About 85% of infected people are children under the age of 15 years. The mortality rate is very low, and infections have been greatly reduced since the development of its vaccine.
Parotitis is the inflammation of one or both of the parotid glands, and the most common cause is mumps. Other bacterial infections can also cause swelling, either by blocking the duct, or following an infection. Inflammation can also be observed following Mikulicz disease and Sjögren syndrome.
Sialolithiasis is the development of salivary stones, within the parotid gland itself, but most frequently in its duct, and that can have many causes.
Parotid gland tumours can either be benign (around 80%) or malignant (around 20%). Benign lesions include hemangiomas, pleomorphic adenomas (which can develop into a malignant form), and lymphatic malformations. Malignant lesions occur less frequently and can extend to the other major salivary glands; those lesions include Mucoepidermoid carcinoma and adenoid cystic carcinoma.
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- Kraaij, S., Karagozoglu, K., Forouzanfar, T. et al. (Salivary stones: symptoms, aetiology, biochemical composition and treatment). Br Dent J 217, E23 (2014) doi:10.1038/sj.bdj.2014.1054.
- Canadian Cancer Society, (Research in salivary gland cancer).
The information above should be used as a reference only. Any medical decision should not be taken before consulting a health care professional.