Salivary glands types , functions and disorders

Salivary glands

The salivary glands in mammals are exocrine glands that produce saliva through ducts. Humans have three paired major salivary glands (parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands .

Between 0.5 and 1.5 litres of saliva are produced every day. The secretion of saliva is mediated by parasympathetic stimulation; acetylcholine is the active neurotransmitter and binds to muscarinic receptors in the glands, leading to increase salivation

The fourth pair of salivary glands, the tubarial glands discovered in 2020 are named for their location, being positioned in front and over the torus tubarius.

Parotid glands

The two parotid glands are major salivary glands wrapped around the mandibular ramus in humans. They are largest of the salivary glands, secreting saliva to facilitate mastication and swallowing, and amylase to begin the digestion of starches. It is the serous type of gland which secretes alpha-amylase (also known as ptyalin). It enters the oral cavity via the parotid duct or Stenson's 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. They produce 20% of the total salivary content in the oral cavity. Mumps is a viral infection, caused by infection in the parotid gland.

Submandibular glands

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. The secretion produced is a mixture of both serous fluid and mucus, and enters the oral cavity via the submandibular duct or Wharton duct. Approximately 65-70% of saliva in the oral cavity is produced by the submandibular glands, even though they are much smaller than the parotid glands. 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.

Sublingual glands

The sublingual glands are a pair of major salivary glands located inferior to the tongue, anterior to the submandibular glands. The secretion produced is mainly mucous in nature; however, it is categorized as a mixed gland. 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,the largest one is called Bartholin's duct.

Approximately 5% of saliva entering the oral cavity comes from these glands.

What are the benefits of saliva ?

Protection

Saliva consists of proteins (for example; mucins) that lubricate and protect both the soft and hard tissues of the oral cavity. Mucins are the principal organic constituents of mucus, the slimy visco-elastic material that coats all mucosal surfaces.

Buffering

In general, the higher the saliva flow rate, the faster the clearance and the higher the buffer capacity, hence better protection from dental caries. Therefore, people with a slower rate of saliva secretion, combined with a low buffer capacity, have lessened salivary protection against microbes.

Pellicle formation

Saliva forms a pellicle on the surface of the tooth to prevent wearing. The film contains mucins and proline-rich glycoprotein from the saliva. The proteins (statherin and proline-rich proteins) within the salivary pellicle inhibit demineralisation and promote remineralisation by attracting calcium ions.

Maintainance of tooth integrity

Demineralization occurs when enamel disintegrates due to the presence of acid. When this occurs, the buffering capacity effect of saliva (increases saliva flow rate) inhibits demineralisation. Saliva can then begin to promote the remineralisation of the tooth by strengthening the enamel with calcium and phosphate minerals.

Antimicrobial action

Saliva can prevent microbial growth based on the elements it contains. For example, lactoferrin in saliva binds naturally with iron. Since iron is a major component of bacterial cell walls, removal of iron breaks down the cell wall, which in turn breaks down the bacterium. Antimicrobial peptides such as histatins inhibit the growth of Candida albicans and Streptococcus mutans. Salivary Immunoglobulin A serves to aggregate oral bacteria such as S. mutans and prevent the formation of dental plaque.

Tissue repair

Saliva can encourage soft tissue repair by decreasing clotting time and increasing wound contraction.

Digestion

Saliva contains the enzyme amylase, which hydrolyses starch into maltose and dextrin. As a result, saliva allows digestion to occur before the food reaches the stomach.

Taste

Saliva acts as a solvent in which solid particles can dissolve in and enter the taste buds through oral mucosa located on the tongue. These taste buds are found within foliate and circumvallate papillae, where minor salivary glands secrete saliva

What are salivary gland disorders?

A number of diseases can affect your salivary glands. These range from cancerous tumors to Sjögren’s syndrome. While some conditions go away with time or antibiotics, others require more serious treatments, including surgery.

Salivary gland infection

Salivary gland infection is also called sialadenitis. Most salivary gland infections occur in people who have something that blocks the flow of saliva (such as a stone) or who have very low flow of saliva. Infection is most common in the parotid gland and typically occurs in people who

Are in their 50s and 60s

Have a chronic illness and dry mouth

Have Sjögren syndrome

Have had radiation therapy to the mouth area or radioactive iodine therapy for thyroid cancer

Adolescents and young adults with anorexia are also prone to this infection. The usual infecting organism is the bacteria Staphylococcus aureus.

People with a bacterial infection of a salivary gland have fever, chills, and pain and swelling on the side of the face with the infected gland. The skin over the infected gland becomes red and swollen. Sometimes a collection of pus (abscess) forms in the gland, and a small amount of pus comes out of the duct of the gland.

Sialolithiasis and sialadenitis

Sialolithiasis occurs when stones made of calcium form in the salivary glands. These stones can block the glands, and that can partially or completely stop the flow of saliva. Most commonly affect submandibular gland as it's long and somewhat tortous duct .

A stone can form from salts contained in the saliva. Stones are particularly likely to form when people are dehydrated or take drugs that decrease saliva production. People with gout are also more likely to form stones. Salivary gland stones are most common among adults. About 25% of people with stones have more than one.

Salivary stones create problems when they block the tube (duct) that carries saliva from the gland to the mouth. Blockage makes saliva back up inside the duct, causing the salivary gland to swell painfully. A blocked duct and gland filled with stagnant saliva may become infected with bacteria.

Sialadenitis is an infection involving a salivary gland. It often results from stones blocking the gland. Staph or strep bacteria can cause this infection. Older adults and infants are most likely to develop this condition.

Sjögren’s syndrome

Sjögren’s syndrome is another common salivary gland disorder. It occurs when white blood cells target healthy cells in moisture-producing glands, such as the salivary, sweat, and oil glands. This condition most commonly affects women with autoimmune disorders, such as lupus.

Viruses

Viruses can affect the salivary glands as well. These include:

flu virus

mumps

Coxsackie virus

echovirus

cytomegalovirus

Cancerous and noncancerous tumors

Cancerous and noncancerous tumors may develop in the salivary glands as well. Cancerous tumors of the salivary glands are rare. When they do occur, it’s typically in 50- to 60-year-olds, according to Cedars-Sinai.

Noncancerous tumors that can affect the parotid glands include pleomorphic adenomas and Warthin’s tumors. Benign pleomorphic adenomas can also grow in the submandibular gland and the minor salivary glands, but this is rare.

Mumps is a viral infection that primarily affect parotid glands , along with other parts of the body. Mumps can cause swelling in one or both of these glands.

Mumps was common in the United States until mumps vaccination became routine. Since then, the number of cases has dropped dramatically.

Swelling also can result from cancerous (malignant) or noncancerous (benign) tumors in the salivary glands. Swelling resulting from a tumor is usually firmer than that caused by an infection. If the tumor is cancerous, the gland may feel stone-hard and may be fixed firmly to surrounding tissues (see Mouth and Throat Cancer ). Most noncancerous tumors are moveable.

An injury to the lower lip—for instance, from accidental biting—may harm any of the minor salivary glands found there and block the flow of saliva. As a result, an affected gland may swell and form a small, soft lump (mucocele) that appears bluish. The lump usually disappears by itself within a few weeks to months.

Dry Mouth

Many older people have a dry mouth. Although aging itself affects moisture in the mouth only slightly, it does make people more susceptible to conditions that dry the mouth, and older people are more likely to take drugs that may dry the mouth.

For many people, a dry mouth is only an occasional annoyance. For others, it is a persistent problem that interferes with tasting, chewing, swallowing, speaking, and wearing dentures. Persistent dry mouth increases the risk of tooth decay and periodontal disease. Persistent dry mouth is usually a symptom of a disorder or a side effect of a drug.

What are the symptoms of a salivary gland disorder?

The symptoms of sialolithiasis include:

painful lump under the tongue

pain that increases when eating

Sialadenitis symptoms include:

lump in your cheek or under your chin

pus that drains into your mouth

strong or foul-smelling pus

fever

Cysts that grow in your salivary glands can cause:

yellow mucus that drains when the cyst bursts

difficulty eating

difficulty speaking

difficulty swallowing

Viral infections in the salivary glands, such as mumps, can cause:

fever

muscle aches

joint pain

swelling on both sides of the face

headache

The symptoms of Sjögren’s syndrome include:

dry mouth

dry eyes

tooth decay

sores in the mouth

joint pain or swelling

dry cough

unexplained fatigue

swollen salivary glands

frequent salivary gland infections

If you have diabetes or alcoholism, you may also have swelling in the salivary glands.

Diagnosis of Salivary Gland Disorders

Biopsy

Endoscopy

Imaging studies

For infection, culture of pus from the salivary gland duct

There are no good tests to measure saliva production. However, the salivary glands can be squeezed (milked), and the ducts can be observed for saliva flow.

Swelling due to blockage of a salivary duct is diagnosed because of the relationship of pain to eating or drinking something that stimulates saliva flow. To diagnose other causes of swelling, a dentist or doctor may do a biopsy to obtain a sample of salivary gland tissue and examine it under a microscope. Other causes of blockage may be identified by newer techniques that use very small viewing tubes (endoscopes) that can be inserted into the salivary gland ducts.

If doctors are not able to make the diagnosis during the physical examination, they may do certain imaging studies, such as computed tomography (CT), ultrasonography, and sialography. Sialography is a type of x-ray that is taken after a dye that is visible on x-rays has been injected into the salivary glands and ducts.

If infection is suspected, doctors look for inflammation on imaging tests, such as a computed tomography (CT) scan, ultrasonography, or magnetic resonance imaging (MRI). If the doctor can squeeze pus from the duct of the affected gland, it is cultured (sent to the laboratory to try to grow bacteria).

Treatment of Salivary Gland Disorders

For dry mouth, good dental hygiene and sometimes drugs as pilocarpine parasympathomimetic .

For stones, pain relievers, fluids, physical measures, or sometimes removal

For infection, antibiotics and physical measures

For swelling, various treatments, possibly including surgery

For dry mouth, people should

Avoid drugs that decrease saliva production

Sip fluids throughout the day

Brush and floss regularly

Use fluoride rinses

Visit their dentist for examination and cleaning every 3 to 4 months

Sometimes a saliva substitute containing carboxymethylcellulose as a mouthwash

Sometimes chew sugarless gum or suck on xylitol lozenges

Some dentists have people wear plastic tooth covers filled with fluoride gel at night to prevent tooth decay due to dry mouth. Sometimes, drugs that increase saliva production, such as cevimeline or pilocarpine, help relieve symptoms. Such drugs may not help when the salivary glands have been damaged by radiation.

For salivary gland stones, people can take pain relievers (analgesics), drink extra fluids, massage the glands, apply warm compresses, and trigger saliva flow with lemon juice or wedges, sour candy, or a combination. If the stone does not pass on its own, a dentist can sometimes push the stone out by pressing on both sides of the duct. If that fails, a fine-wire‒like instrument can be used to pull out the stone. As a last resort, the stone can be removed surgically or through an endoscope.

For salivary gland infection, doctors give antibiotics and have people massage the glands and apply warm compresses. A salivary abscess needs to be cut open and drained. Staying hydrated, triggering saliva with lemon juice and hard candies, and having good oral hygiene are also important.

Salivary gland swelling treatment varies with the cause. A mucocele that does not disappear on its own can be removed surgically if it becomes bothersome. Similarly, both noncancerous and cancerous salivary gland tumors can usually be removed surgically.

Related topics :

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👆Oral biopsy

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👆 principles of smile design

Books

Atlas of oral histology