The submandibular gland, also called the mandibular salivary gland, is one of the three major salivary glands. It is paired at the angle of the mandible. Its excretory ducts open into the oral cavity to the left and right of the lingual frenulum.
What is submandibular gland?
Together with the parotid gland (glandula parotidea) and the sublingual gland (glandula sublingualis), the submandibular gland is one of the three major salivary glands. It is a seromucous gland, meaning that the secretions of the sublingual gland contain both serum-like (serous) and mucous (mucous) components. The submandibular gland is the source of most saliva.
Anatomy and structure
The submandibular glandula is located in the floor of the mouth on the inside of the mandible. More specifically, it lies just between the mandible and the digastric muscle, a muscle of the head. The mandible and the digastric muscle form the so-called trigonum submandibulare at this point. The gland is embedded here in the superficial sheet of the cervical fascia (fascia cervicalis or fascia colli). The posterior part of the submandibular gland includes the posterior border of the maxillary hyoid muscle (Musculus mylohyoideus). The excretory duct of the gland, the submandibular duct or Wharton’s duct, opens below the tongue, as does the sublingual gland. The exact location is on the side of the lingual frenulum on the hunger wart (caruncula sublingualis). The submandibular gland belongs to the mixed seromucous salivary glands. It exhibits a tubuloacinar structure. Tubuloacinar glands can be recognized by their branched tubular system of glandular ducts. The glandular ducts terminate in berry-shaped terminals, the acini. In the submandibular gland, the serous acini predominate. Between these are only occasional mucous glandular tubes. These produce the mucous portion of saliva. The submandibular salivary gland receives parasympathetic nerve supply from nucleus salivatorius superior. Sympathetic nerve fibers extend from the cervical superior ganglion to the salivary gland.
Function and Tasks
The main function of the submandibular gland is the production of saliva. The parotid gland produces only serous saliva. This saliva is therefore very fluid and watery and has no mucilaginous additives. The secretion of the submandibular gland is predominantly mucous. The saliva produced by the submandibular gland is a mixture of both. It has both mucous and serous components. Approximately 0.6 to 1.5 liters of saliva are produced per day in all three salivary glands in an adult human. Salivation, i.e. saliva production, depends on the amount of food consumed. Saliva is also constantly produced without the intake of food. This is referred to as basal secretion. This is about half a liter of saliva per day. The submaxillary salivary gland produces the most saliva. The saliva produced in the salivary glands consists mainly (99.5%) of water. This water contains so-called mucins, proteins, digestive enzymes, antibodies and minerals. The mucins give the saliva of the submandibular gland its mucilaginous form. They protect the mucous membranes of the oral cavity from chemical and mechanical effects. They also ensure the viscosity of the saliva and make the food pulp more slippery, so that it can pass more easily through the esophagus into the stomach. Ptyalin, also known as alpha-amylase, which is produced in the submandibular glandula, is a digestive enzyme responsible for the predigestion of carbohydrates. The digestion of food therefore already begins in the mouth due to the alpha-amylase contained in saliva. Due to the substances it contains, such as immunoglobulins, lactoferrin or lysozyme, saliva also has an antibacterial effect. Moreover, without the saliva produced in the salivary glands, swallowing, speaking and tasting would not be possible at all. Smelling is also influenced by saliva.
Diseases
If too much saliva is produced in the salivary gland, this is called hypersalivation. This can occur physiologically by irritation of the taste buds, olfactory nerves, gastric and intestinal nerves, or optic nerves. However, diseases of the salivary glands and oral cavity as well as poisoning can also result in increased salivation.Dry mouth, caused by too little saliva, often occurs in old age. However, radiation therapy or certain diseases, such as Sjögren’s syndrome, can also cause dry mouth (xerostomia). Sjögren’s syndrome is an autoimmune disease in which the immune system attacks the salivary glands, among other organs. Nearly 100% of all Sjögren’s patients suffer from dry mouth. If the salivary gland is swollen and painful, there is usually an inflammation. The parotid gland is most commonly affected by inflammation, but the submandibular gland can also become inflamed. The most common cause of inflammation of the submandibular gland is infection with bacteria such as staphylococci or streptococci. In this case, the germs migrate through the insertion ducts into the interior of the gland and cause a defensive reaction there. This then manifests itself in the form of inflammation. The salivary gland is particularly susceptible to such inflammations when it produces little saliva. That is why salivary gland inflammations mostly affect older people. However, poor oral hygiene, malnutrition or inflammation of the oral mucosa also promote salivary gland inflammation. Salivary gland inflammation is often associated with salivary stones. The submandibular gland is the salivary gland where most salivary stones form. Eight out of ten salivary stones form here. These stones consist largely of magnesium and calcium phosphate. They can grow up to five centimeters in size. Salivary stones cause the salivary gland to swell. Possible pain worsens when saliva production increases, such as during chewing. Salivary gland inflammation caused by salivary stones can result in an abscess. In the worst case, this leads to blood poisoning.
