The salivary gland is a term used to collectively describe an extensive set of glands throughout the mouth and throat. The major purpose of these glands is the secretion of saliva. Saliva is a mixture of water, mucus, antibacterial agents and enzymes that is secreted by most mammals. This substance begins the breakdown of starch and fats that, along with chewing, begins the digestive process.
The salivary gland is made up of three major pairs of glands: the parotid glands, the submandibular glands, and the sublingual glands. The parotid glands are responsible for the production of approximately 20-25% of saliva. They are located over the back portion of the mandible (the jaw) on either side of the head. The submandibular glands are located under the floor of the mouth. They are responsible for the production of around 70% of saliva. The sublingual glands are located beneath the floor of the mouth in front of the submandibular glands. They are responsible for the production of only about 5% of saliva.
There are between 600 and 1,000 minor glands located throughout the mouth and throat that are considered part of the salivary gland. They are located beneath the moist skin that lines the oral cavity. Their major function, though certainly not their only function, is mucous production for the purposes of keeping the mouth and throat appropriately coated with saliva.
The salivary gland is composed of three kinds of cells: mucous, serous, and myoepithelial cells. Mucous cells are shaped like cubes and secrete mucus that has glycoproteins (a lubricant). Serous cells tend to have a somewhat pyramid shape and cluster in a spherical group referred to as an acinus. They secrete serous fluid that has amylase (an enzyme that helps with carbohydrate digestion.) Myoepithelial cells surround the areas where saliva is actually secreted. They can contract which increases the amount of saliva produced.
Dysfunction in the salivary gland can result in a number of conditions:
o Sialolithiasis-This is a condition in which stones called sialoliths or salivary calculi, form inside the glands. The cause is unknown but may be exacerbated by dehydration.
o Sialadenitis- This is when a bacterial infection takes hold in the glands. The bacteria that usually cause the infection are staphylococcus, streptococcus, Haemophilus influenzae. It is most common in the elderly and the risks are increased by dehydration, surgery, cancer, medications, and malnutrition.
o Viral infections- Viral infections that affect the entire body will sometimes settle in the glands which can result in facial swelling, pain and difficulty eating.
o Tumors- Tumors in these glands can be malignant or benign. The vast majority of tumors in these glands are benign and found in the parotid glands. Malignant tumors in these glands are quite rare and usually found in middle aged patients. There are very few risk factors for malignant tumors aside from radiation exposure or Sjogren’s Syndrome.