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Salivary 2021


The salivary glands in mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands (parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands.[1] Salivary glands can be classified as serous, mucous, or seromucous (mixed).




salivary



A proposed fourth pair of salivary glands, the tubarial glands, were first identified in 2020. They are named for their location, being positioned in front of and over the torus tubarius. However, this finding from one study is yet to be confirmed.[5]


The two parotid glands are major salivary glands wrapped around the mandibular ramus in humans.[6] These are largest of the salivary glands, secreting saliva to facilitate mastication and swallowing, and amylase to begin the digestion of starches.[7] It is the serous type of gland which secretes alpha-amylase (also known as ptyalin).[8] It enters the oral cavity via the parotid duct. The glands are located posterior to the mandibular ramus and anterior to the mastoid process of the temporal bone. They are clinically relevant in dissections of facial nerve branches while exposing the different lobes, since any iatrogenic lesion will result in either loss of action or strength of muscles involved in facial expression.[8] They produce 20% of the total salivary content in the oral cavity.[7] Mumps is a viral infection, caused by infection in the parotid gland.[9]


The submandibular glands (previously known as submaxillary glands) are a pair of major salivary glands located beneath the lower jaws, superior to the digastric muscles.[6] The secretion produced is a mixture of both serous fluid and mucus, and enters the oral cavity via the submandibular duct or Wharton duct.[7] Around 70% of saliva in the oral cavity is produced by the submandibular glands, though they are much smaller than the parotid glands.[7] This gland can usually be felt via palpation of the neck, as it is in the superficial cervical region and feels like a rounded ball. It is located about two fingers above the Adam's apple (laryngeal prominence) and about two inches apart under the chin.


The sublingual glands are a pair of major salivary glands located inferior to the tongue, anterior to the submandibular glands.[6] The secretion produced is mainly mucous in nature, but it is categorized as a mixed gland.[8] Unlike the other two major glands, the ductal system of the sublingual glands does not have intercalated ducts and usually does not have striated ducts, either, so saliva exits directly from 8-20 excretory ducts known as the Rivinus ducts.[8] About 5% of saliva entering the oral cavity comes from these glands.[7]


The tubarial glands are suggested as a fourth pair of salivary glands situated posteriorly in the nasopharynx and nasal cavity, predominantly with mucous glands, and its ducts opening into the dorsolateral pharyngeal wall. The glands were unknown until September 2020, when they were discovered by a group of Dutch scientists using with prostate-specific membrane antigen PET-CT. This discovery may explain mouth dryness after radiotherapy despite the avoidance of the three major glands. However, these findings from just one study need to be confirmed.[10][5] On the other hand, an interdisciplinary group of scientists disagree with this new discovery. They believe that an accumulation of minor salivary glands has been described.[11]


Around 800 to 1,000 minor salivary glands are located throughout the oral cavity within the submucosa[12] of the oral mucosa in the tissue of the buccal, labial, and lingual mucosa, the soft palate, the lateral parts of the hard palate, and the floor of the mouth or between muscle fibers of the tongue.[13] They are 1 to 2 mm in diameter and unlike the major glands, they are not encapsulated by connective tissue, only surrounded by it. The gland has usually a number of acini connected in a tiny lobule. A minor salivary gland may have a common excretory duct with another gland, or may have its own excretory duct. Their secretion is mainly mucous in nature and have many functions such as coating the oral cavity with saliva. Problems with dentures are sometimes associated with minor salivary glands if dry mouth is present.[12] The minor salivary glands are innervated by the seventh cranial or facial nerve.[13]


All of the human salivary glands terminate in the mouth, where the saliva proceeds to aid in digestion. The released saliva is quickly inactivated in the stomach by the acid that is present, but saliva also contains enzymes that are actually activated by stomach acid.


About 20,000 protein-coding genes are expressed in human cells and 60% of these genes are expressed in normal, adult salivary glands.[19][20] Less than 100 genes are more specifically expressed in the salivary gland. The salivary gland specific genes are mainly genes that encode for secreted proteins and compared to other organs in the human body; the salivary gland has the highest fraction of secreted genes. The heterogeneous family of proline-rich, human salivary glycoproteins, such as PRB1 and PRH1, are salivary gland-specific proteins with highest level of expression. Examples of other specifically expressed proteins include the digestive amylase enzyme AMY1A, the mucin MUC7 and statherin, all of major importance for specific characteristics of saliva.


Salivary glands secrete saliva, which has many benefits for the oral cavity and health in general. The knowledge of normal salivary flow rate (SFR) is extremely important when treating dental patients.[23] These benefits include:


Salivary gland dysfunction refers to either xerostomia (the symptom of dry mouth) or salivary gland hypofunction (reduced production of saliva); it is associated with significant impairment of quality of life.[34] Following radiotherapy of the head and neck region, salivary gland dysfunction is a predictable side-effect.[34] Saliva production may be pharmacologically stimulated by sialagogues such as pilocarpine and cevimeline.[35] It can also be suppressed by so-called antisialagogues such as tricyclic antidepressants, SSRIs, antihypertensives, and polypharmacy.[36] A Cochrane review found there was no strong evidence that topical therapies are effective in relieving the symptoms of dry mouth.[37]


Cancer treatments including chemotherapy and radiation therapy may impair salivary flow.[37][34] Radiotherapy can cause permanent hyposalivation due to injury to the oral mucosa containing the salivary glands, resulting in xerostomia, whereas chemotherapy may cause only temporary salivary impairment.[37][34] Furthermore surgical removal because of benign or malignant lesions may also impair function.[38]


The salivary glands of some species are modified to produce proteins; salivary amylase is found in many bird and mammal species (including humans, as noted above). Furthermore, the venom glands of venomous snakes, Gila monsters, and some shrews, are actually modified salivary glands.[36] In other organisms such as insects, salivary glands are often used to produce biologically important proteins such as silk or glues, whilst fly salivary glands contain polytene chromosomes that have been useful in genetic research.[42]


Your salivary glands are in your mouth. You have three pairs of major salivary glands and hundreds of small (minor) glands. They make saliva (spit) and empty it into your mouth through openings called ducts. Saliva makes your food moist, which helps you chew and swallow. It helps you digest your food. It also cleans your mouth and contains antibodies that can kill germs.


Your salivary glands produce saliva (spit) and empty it into your mouth through ducts, or small openings. They lubricate your mouth and throat, aid in swallowing and digestion, and help shield your teeth from cavity-causing bacteria.


Your salivary glands produce saliva, which aids the digestion process. When you eat, the food leaves your mouth and travels down your throat, through your esophagus and eventually makes its way to your stomach. Saliva makes this entire process possible.


In addition to the major salivary glands mentioned earlier, you also have lots of minor salivary glands. These tiny glands are under the lining of your mouth and throat. Each person has up to 1,000 of them. While minor salivary glands are significantly smaller than your major salivary glands, together, they actually produce more saliva than your major glands.


Treatment for salivary gland tumors usually involves removing the mass. If the tumor is cancerous, further treatment is often necessary and may include chemotherapy, radiation therapy, immunotherapy or targeted drug therapy.


The primary symptom of salivary gland conditions is dry mouth. If you have dry mouth, ask your healthcare provider about treatment options. If medications are causing dry mouth, your provider might be able to switch your prescriptions or decrease your dosages. They may also recommend products that can help keep your mouth lubricated.


If your healthcare provider suspects you have a salivary gland issue, they may recommend a salivary gland scan. This test uses a specialized camera and a radioactive tracer to capture images of your salivary glands.


Before the scan, your provider injects the liquid tracer into a vein in your arm. The liquid moves through your blood and then into your salivary glands. Next, the camera takes pictures that tell your provider how much of the liquid stays in your salivary glands. This test is often used to diagnose dry mouth or salivary gland swelling.


If you have salivary gland cancer or are close to someone who does, knowing what to expect can be helpful. Here you can find out all about salivary gland cancer, including risk factors, symptoms, how it is found, and how it is treated.


Saliva is a highly versatile biological fluid that is easy to gather in a non-invasive manner-and the results of its analysis complement clinical and histopathological findings in the diagnosis of multiple diseases. The objective of this review was to offer an update on the contribution of salivary biomarkers to the diagnosis and prognosis of diseases of the oral cavity, including oral lichen planus, periodontitis, Sjögren's syndrome, oral leukoplakia, peri-implantitis, and medication-related osteonecrosis of the jaw. Salivary biomarkers such as interleukins, growth factors, enzymes, and other biomolecules have proven useful in the diagnosis and follow-up of these diseases, facilitating the early evaluation of malignization risk and the monitoring of disease progression and response to treatment. However, further studies are required to identify new biomarkers and verify their reported role in the diagnosis and/or prognosis of oral diseases.


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