Salivary Glands

Salivary Glands

Overview and Definition

The salivary glands are exocrine glands that produce a digestive fluid called saliva. They are accessory organs of the digestive system and are positioned in the head, in and around the oral cavity, secreting their salivary contents into the mouth. Saliva is a seromucinous liquid that has several major functions within the oral cavity, including lubrication, digestion, antimicrobial action, buffering, hormone regulation, and taste sensation.

Anatomy: Major and Minor Glands

The salivary glands are divided into the major and minor salivary glands. The major glands include the parotid, submandibular, and sublingual glands. In addition, 600–1,000 tiny glands (the minor salivary glands) are located in the lips, inner cheek, and the lining of the mouth and throat.

Parotid Glands

The parotid glands are the largest of the three paired salivary glands. The parotid gland makes approximately 25 percent of the saliva and drains into the mouth near the upper teeth. The parotid glands contain serous acini. In humans, 20% of individuals possess an accessory parotid gland, equipped with its own blood supply and a secondary excretory duct independent from the main body of the gland.

Submandibular Glands

The submandibular gland makes approximately 70 percent of the saliva and drains into the mouth from under the tongue. The submandibular glands are a mix of serous and mucinous acini.

Sublingual Glands

The sublingual glands are the smallest of the three major salivary glands and are between the mylohyoid muscle and mucosa in the anterior portion of the floor of the mouth. The sublingual gland makes approximately 5 percent of the saliva and drains into the floor of the mouth. The sublingual glands are predominantly mucinous acini. The minor salivary glands are mainly mucinous glands, except for the lingual serous glands known as Ebner glands.

Acinar Cell Types and Duct Architecture

Acinar cells are the secretory cells of the salivary gland and are either serous or mucinous. These cells differ in their structure and the content that they produce and secrete. Serous acinar cells are spherical and consist of 8 to 12 cells surrounding a central lumen that produce glycoproteins and proteins which function to bind calcium, act as anti-microbial agents, and complete other enzymatic activities.

Serous cells produce a more watery, enzyme-rich saliva, while mucous cells secrete a more viscous fluid with glycoproteins known as mucins. The intercalated ducts lead into striated ducts, which lead into the excretory columnar epithelium-lined interlobular ducts. The striated ducts are important because they allow for active transport of substances out of the duct, water resorption, and ion secretion to create hypotonic saliva with low sodium and chloride levels and increased carbonate and potassium levels.

Physiological Functions

Digestion

Salivation plays a vital role in digestion, as digestion of food begins in the mouth. The salivary submandibular, parotid, sublingual, and submucosal glands produce saliva which is necessary for the moistening of food products, breakdown of carbohydrates by salivary amylase (formerly known as ptyalin), antimicrobial, and other protective mechanisms. This initial phase of digestion and lubrication is essential for the passage of food from the oropharynx to the esophagus and stomach.

Lubrication and Bolus Formation

Functionally, the salivary glands contribute to digestion through the enzymes they excrete with saliva, mainly amylase, which starts the digestion of carbohydrates. They also help in the initial stages of digestion during mastication of food, so that a food bolus is created and ready to be swallowed for further processing. Additionally, they help keep the oral mucosa protected and lubricated.

Antimicrobial Defense

Saliva also starts the digestion of starch because it contains an enzyme called amylase. Saliva also acts as 'nature's mouthwash,' since it is rich in antimicrobial compounds such as hydrogen peroxide to keep mouths clean. Saliva supplied from the salivary glands into the oral cavity contains various substances, such as mucus and antibacterial substances, and has an essential function as one of the host's defense mechanisms.

Mucin and Mucosal Hydration

Sialic acid and sulfate residues give mucins a net negative charge, creating an extended configuration and rendering them water retentive, thus playing a role in mucin hydration. Mucins are therefore integral to rendering saliva its rheological properties such as viscosity, elasticity, and stickiness.

Circadian Rhythm and Reflex Secretion

Secretions can be increased by the presence, thought, or smell of food and by thermal stimulation. Salivary flow also exhibits a circadian rhythm, leading to variations at different times of the day and night. Reflex salivary flow occurs at a low 'resting' rate, and for short periods of the day more intense taste or chewing stimuli evoke up to tenfold increases in salivation.

Salivary Diagnostics

The intricate composition of saliva comprises proteins, electrolytes, enzymes, hormones, and microbial DNA, enabling it to act as a dynamic indicator of both local and systemic health. Saliva-based testing is a commonly used noninvasive tool for the diagnosis of viral infections such as SARS-CoV-2. Other viruses such as Epstein-Barr virus, hepatitis B virus, Ebola, rabies, and HIV can also be detected in oral fluids.

Neural Regulation of Secretion

The salivary glands are under autonomic control by both sympathetic and parasympathetic systems. Stimulation of either parasympathetic or sympathetic nervous systems will stimulate salivary gland secretion, but the effects of parasympathetic stimulation are stronger and longer lasting.

The secretion of salivary fluid and proteins is controlled by autonomic nerves. All salivary glands are supplied by cholinergic parasympathetic nerves which release acetylcholine that binds to M3 and (to a lesser extent) M1 muscarinic receptors, evoking the secretion of saliva by acinar cells in the endpieces of the salivary gland ductal tree. In salivary glands, parasympathetic stimulation of M1 and M3 receptors leads to high-volume secretion of potassium ions, water, and amylase.

The salivary glands receive parasympathetic and sympathetic innervation. The parasympathetic innervation leads to serous salivary production and ion secretion, and the sympathetic increases the secretion of proteins. The sympathetic innervation is also known to regulate the blood flow of the glands and local inflammatory and immune mediators.

The parasympathetic innervation to the parotid gland begins at the inferior salivatory nucleus of the glossopharyngeal nerve and synapses on the otic ganglion; postganglionic fibers reach the gland via the auriculotemporal nerve. The parasympathetic innervation to the submandibular and sublingual glands begins in the superior salivatory nucleus with preganglionic fibers of the facial nerve synapsing on the submandibular ganglion, with postganglionic fibers reaching the glands via the lingual nerve. Not only do the nerves stimulate salivary gland secretion, but they may also play a role in the ability of the salivary glands to regenerate, avoid atrophy, and maintain their function.

Assessment of Salivary Gland Health

Clinical Examination and History

A doctor uses the patient's medical history, a physical examination, and laboratory tests to make a diagnosis of a salivary disorder. If pain and inflammation are suspected to result from an obstruction in one of the glands, X-rays or an ultrasound may be ordered to identify the obstruction and its cause. If a mass is found in the salivary gland, a CT scan or an MRI is typically recommended. A fine needle aspiration biopsy may also be performed to remove a small amount of tissue or fluid and check for cancer cells.

Sialometry

The most advocated clinical method for diagnosing salivary dysfunction is to quantitate unstimulated and stimulated whole saliva (sialometry). Since there is an expected and wide variation in salivary flow rates among individuals, the assessment of dysfunction can be difficult. The cut-off value for a very low unstimulated whole saliva flow rate is claimed to be ≤0.1 ml/min and for stimulated whole saliva ≤0.7 ml/min, according to the widely cited literature. Sialometry is a simple, low-cost test and of easy execution as long as the technique is standardized.

Sialochemistry

Glandular sialometry and sialochemistry are not only useful tools for differentiating Sjögren's syndrome from other salivary gland disease in clinical practice, but they also have great potential as diagnostic criteria for the syndrome, showing distinct sialometric and sialochemical changes and profiles. Being simple, safe (non-invasive), and sensitive (early disease detection), they have three major advantages over other oral tests. Both sialometry and sialochemistry are considered essential in complaints of xerostomia, sialorrhea, and the burning mouth syndrome, with particular interest in circulatory disorders of the glands and the use of medicaments.

Scintigraphy

Scintigraphy provides advantages that include saliva quantitative analysis throughout the evaluation of radiopharmaceutical buildup and salivary escape, which may correctly reflect functional alterations and bring information about obstructive clogging of the salivary gland. It may also detect early stages of salivary gland involvement. The need to use diagnostic criteria that involve more than one test is confirmed by this; both sialometry and scintigraphy should be carried out to assess salivary gland involvement in patients complaining of dry mouth, especially in Sjögren's syndrome patients.

Minor Salivary Gland Biopsy

A lip biopsy of minor salivary glands may be needed to identify certain autoimmune diseases, such as Sjögren's disease. Accurate assessment of salivary gland function is essential in the diagnosis and management of various oral and systemic conditions, including xerostomia, Sjögren's syndrome, and adverse effects from medications or radiation therapy. Minor salivary glands, distributed throughout the oral mucosa, provide valuable diagnostic information because their function can reflect subtle changes in salivary secretion that may not be detected by whole saliva flow rates.

Factors Supporting Normal Salivary Gland Function

Hydration

Saliva is essential for the maintenance of oral health. The primary constituent of saliva is water, and decreased body water homeostasis has traditionally been linked with salivary dysfunction. A controlled study published in PubMed demonstrated that body dehydration is associated with decreased parotid salivary gland flow rates, and that these changes are generally age-independent in healthy adults. Furthermore, although subjects were metabolically rehydrated, unstimulated salivary flow rates remained significantly lower than baseline levels, indicating that recovery of salivary function after dehydration may be delayed.

Autonomic Stimulation via Mastication and Taste

Reflex salivary flow occurs at a low 'resting' rate, and for short periods of the day more intense taste or chewing stimuli evoke up to tenfold increases in salivation. Taste and mechanical stimuli, such as peppermint or sugarless gum, are supposed to be involved in treating xerostomia when the salivary gland can still be stimulated.

Zinc

A study published in Scientific Reports investigated the role of the metabotropic zinc receptor ZnR/GPR39 in human submandibular gland cells. Mouth rinsing with ZnCl₂ solution increased unstimulated salivary secretion in healthy normal subjects, hyposalivation patients, and Sjögren's syndrome patients. Zinc (Zn²⁺) is a divalent cation essential for many biological activities, influencing many ion channels and enzymatic activities. Zn²⁺ can evoke G-protein-coupled receptor signaling via activation of the metabotropic zinc receptor ZnR/GPR39. This is preliminary evidence from a small mechanistic clinical study and does not constitute an established therapeutic recommendation.

Conditions and Disorders of the Salivary Glands

Xerostomia (Dry Mouth) and Hyposalivation

The most common clinical finding among salivary gland disorder patients is xerostomia. Xerostomia can be the result of systemic diseases of endocrine, autoimmune, infectious, and granulomatous type among others, in addition to local factors such as the use of certain medications, radiation therapy of the head and neck, and some lifestyle habits such as smoking. Saliva moistens the mouth, lubricates food for easier swallowing, provides enzymes needed to begin the digestive process, and promotes repair and cleansing of soft tissues of the mouth. Decreased salivary production or changes in salivary composition may affect oral and systemic health and cause an increase in tooth decay.

Sialolithiasis (Salivary Stones)

Sialolithiasis is a benign condition involving the formation of stones within the ducts of the major salivary glands. It is the most frequent cause of salivary gland swelling, with a reported incidence of 1 in 10,000 to 1 in 30,000. In some cases, sialoliths can obstruct the salivary ducts, leading to inflammation, superimposed bacterial infection termed sialadenitis, or in rare cases, abscess formation. Sialolithiasis is a condition in which tiny salivary stones form in the glands; the stones, called sialoliths, are made of calcium. The condition predominantly affects individuals between 30 and 60 years and is more common in men. The most frequent symptoms are cyclical gland swelling and pain associated with meals.

Sialadenitis (Salivary Gland Infection)

Sialadenitis can be due to either infectious or noninfectious factors. Bacterial or viral infections are the most common causes of acute sialadenitis. Staphylococcus is the usual bacterial cause, whereas paramyxovirus (mumps) is the common viral cause. Sialadenitis is a painful infection of a salivary gland. Sialadenosis, by contrast, is a painless enlargement of the salivary gland without a known cause, with the parotid gland usually being the affected gland.

Sjögren's Syndrome

Salivary glands are targets for autoimmune diseases such as Sjögren's syndrome, graft-versus-host disease, and the recently described antitumor immune checkpoint inhibitor sicca. Diseases such as HIV/AIDS, and autoimmune disorders such as Sjögren's disease and rheumatoid arthritis, can make the salivary glands inflamed and painful. A lip biopsy of minor salivary glands may be needed to identify certain autoimmune diseases such as Sjögren's disease.

Salivary Gland Tumors

Eighty percent of salivary tumors are benign, whereas about 20% are malignant. Most tumors occur in the parotid gland and on the hard palate. The most common diseases are represented by nonspecific chronic sialadenitis (nonneoplastic lesion), pleomorphic adenoma and Warthin tumor (benign tumors), mucoepidermoid carcinoma (malignant tumor), and squamous carcinoma (secondary tumor). The commonest benign tumor, pleomorphic adenoma, has a malignant transformation potential, and, although considered benign, there is a propensity for recurrence after treatment.

Mucoepidermoid carcinoma is the most frequent malignant tumor. The average annual age-adjusted incidence rate per 100,000 was 4.7 for benign tumors and 0.9 for malignant tumors. The clinical presentation of parotid gland cancers is similar to that of benign parotid gland tumors. Most patients present with a painless palpable mass in the parotid or submandibular gland. However, certain clinical symptoms such as pain, facial nerve palsy, and enlarged lymph nodes may suggest malignancy of the parotid gland.

Radiation-Induced Salivary Gland Damage

The adverse impact of developing late tissue damage in irradiated patients may range from bothersome symptoms that negatively affect their quality of life to severe life-threatening complications. In the region of the head and neck, among the most problematic late effects are impaired function of the salivary glands and swallowing apparatus. Certain disease states, drugs, and radiation therapy can affect the proper functioning of salivation.

Systemic Disease Associations

Other systemic disorders, including HIV/AIDS, autoimmune disorders such as Sjögren's disease and rheumatoid arthritis, can make the salivary glands inflamed and painful. Diabetes may also cause enlargement of the salivary glands. A study on women with Hashimoto's thyroiditis evaluated the redox homeostasis of the salivary glands; data demonstrated that salivary secretion is impaired in patients with Hashimoto's thyroiditis, and the release of oxidant molecules was significantly higher in patients compared to healthy controls.

Nutrients, Herbs, and Natural Ingredients

Overview of the Evidence Landscape

Systematic review synthesis has covered approaches to managing xerostomia and hyposalivation. Herbal therapies have attracted increasing attention as natural, potentially effective substitutes for conventional xerostomia treatments. A systematic review synthesized data from fifteen clinical studies and systematic reviews assessing herbal interventions — such as aloe vera, ginger, peppermint, tea catechins, manuka honey, Chinese herbal medicine, traditional Asian formulations, and combination plant therapies.

According to the research, the majority of herbal treatments show clinically significant reductions in xerostomia symptoms, particularly in subjective dryness ratings. However, objective salivary flow results continue to differ between experiments.

Ginger (Zingiber officinale)

Traditional Use: Ginger has a long history of use in traditional Ayurvedic and East Asian medicine systems for digestive complaints and oral conditions.

Scientific Evidence: Research has substantiated that ginger augments salivary secretion by engaging parasympathetic activity on the postsynaptic M3 receptors and exerting a suppressive influence on presynaptic muscarinic autoreceptors. Ginger has anti-inflammatory and antioxidant properties, and can be used in the treatment of many oral disorders. The presence of ginger in the oral cavity increases salivation and stimulates the salivary glands to produce more saliva. The studies conducted on the effect of ginger on xerostomia are limited, so further investigations are needed. A triple-blind, randomized clinical trial published in Medicina Oral, Patología Oral y Cirugía Bucal compared ginger and aloe vera mouthwashes in patients with type 2 diabetes-related xerostomia, with both interventions demonstrating improvements in subjective dryness.

Aloe Vera (Aloe barbadensis)

Traditional Use: Aloe vera has been used in traditional medicine across Africa, the Caribbean, and the Middle East as a topical gel for wound healing and mucosal protection.

Scientific Evidence: Aloe vera is a medicinal plant with more than 75 active ingredients in its inner gel. About 99% of the gel in aloe vera leaves is water, so it has a strong moisturizing effect. Mucopolysaccharides in the gel help in binding moisture to the skin and mucosa of the mouth. There are very few studies conducted on the effects of aloe vera on xerostomia. A small triple-blind randomized clinical trial examined aloe vera combined with peppermint essential oil as a moisturizing gel in ICU patients with dry mouth, representing early-stage clinical evidence. Evidence for aloe vera in salivary gland function is preliminary and limited to small clinical trials, requiring larger and more rigorous study designs.

Tea Catechins (Camellia sinensis)

Traditional Use: Green tea has been consumed for centuries in East Asia, and is a cornerstone of traditional Chinese and Japanese wellness practices.

Scientific Evidence: A catechin-containing natural formulation resulted in a statistically significant increase in unstimulated (3.8-fold) and stimulated (2.1-fold) saliva output versus baseline. The quality of life score showed significant improvement in both groups. The authors concluded that the catechin-containing natural formula partially restored salivary function in patients with xerostomia and provided an objective improvement in saliva output, warranting large-scale clinical trials. This evidence is preliminary, deriving from a single small trial, and large-scale confirmatory studies are not yet available.

Traditional Chinese Herbal Formulas

Traditional Use: Xerostomia (dry mouth) is caused by salivary hypofunction. Traditional Chinese Medicine (TCM) has been used in the treatment of xerostomia. Formulas such as Liu-wei-di-huang-wan (Yukmijihwang-tang) and Sha Shen Mai Dong Tang have been used in Chinese and Korean medicine for dryness conditions attributed to "Yin deficiency."

Scientific Evidence: A systematic review of 25 randomized controlled trials involving 1,586 patients examined herbal medicines for xerostomia in cancer patients. Twenty-five randomized controlled trials involving 1,586 patients met the inclusion criteria. A total of 24 formulas were examined. Most of the included trials were insufficiently reported in the methodology section. Five formulas were shown to significantly improve the salivary flow rate compared to comparators. Regarding the grade of xerostomia, all formulas with the exception of a Dark Plum gargle solution with normal saline were significantly effective in reducing the severity of dry mouth. Systematic reviews and randomized controlled trials have highlighted the benefits of traditional Chinese herbal medicines, including formulas such as Liu-wei-di-huang-wan and Sha Shen Mai Dong Tang, composed of plants like Ophiopogon japonicus, Adenophora/Glehnia root, Rehmannia glutinosa, and Prunus mume. These remedies have been shown to improve subjective dryness, enhance salivary flow, and alleviate radiation-induced oral complications. Evidence is considered preliminary to moderate given limitations in trial methodology and reporting quality.

Omega-3 Fatty Acids

Traditional Use: Marine-sourced oils have been traditionally used in North Atlantic and Scandinavian folk medicine for systemic inflammatory complaints. Omega-3 fatty acids were not historically associated with salivary glands, but their anti-inflammatory properties have prompted modern investigation.

Scientific Evidence: A randomized, double-blind, placebo-controlled clinical trial published in 2025 assessed omega-3 fatty acids in 104 patients with Sjögren's syndrome over two months. Sialometry tests indicated normalization of salivary flow rate in the omega-3 group, and omega-3 fatty acids effectively improved dry mouth and dry eye symptoms, leading to significant normalization of salivary flow rate. The evidence is preliminary; this is a single trial in a specific population (Sjögren's syndrome), and the sialometry result did not reach the conventional significance threshold (p = 0.053), underscoring the need for replication in larger studies.

Acupuncture (Non-Pharmacological Intervention)

Traditional Use: Acupuncture is part of Traditional Chinese Medicine, a system with an empirical basis which has been used in the treatment and prevention of disease for centuries.

Scientific Evidence: Reports suggest that acupuncture may be effective in treating xerostomia. Acupuncture has been shown to increase salivary flow in healthy volunteers, in patients with Sjögren's syndrome, and in patients with radiation-induced salivary gland injury. A meta-analysis published in 2025 evaluated the efficacy of acupuncture in managing radiation-induced xerostomia. The meta-analysis revealed moderate improvements in both resting and stimulated salivary flow rates, as well as reductions in the frequency and severity of dry mouth symptoms. Several encouraging reports have been published using acupuncture to stimulate saliva flow among radiation-induced xerostomia patients. These studies were conducted in different countries, by different investigators, using different acupuncture points, yet all produced similar positive results. One study demonstrated long-term effect (>3 years) of saliva production. The overall evidence is classified as moderate quality; heterogeneity in study design and acupuncture protocols limits definitive conclusions.

Mechanical Salivary Stimulants: Citric and Malic Acids, Xylitol

Traditional Use: Sour foods and chewing fibrous materials have been used across many cultures to stimulate saliva flow.

Scientific Evidence: Salivary stimulants containing acidic substances, such as citric and malic acids, are used to stimulate glandular secretion. These sialagogues are often enriched by sodium fluoride or xylitol to reduce the risk of demineralization by lowering saliva pH. Gustatory substances and aromas are also included in sucking pastilles and chewing gums to mechanically increase the release of saliva. However, the substances tend to precipitate as complex gelatinous mixtures on oral surfaces rather than being solubilized in saliva fluid to stimulate the activity of the salivary glands; this results in a minimal secretory stimulus for chemoreceptors, as evidenced in several trials. Evidence for these sialagogues is mixed, with variable and typically modest clinical effects.

References

• Physiology, Salivation — StatPearls, NCBI Bookshelf (NIH)
• Anatomy, Head and Neck, Salivary Glands — StatPearls, NCBI Bookshelf (NIH)
• Saliva and Salivary Gland Disorders — National Institute of Dental and Craniofacial Research (NIDCR)
• Physiology, Pathology and Regeneration of Salivary Glands — MDPI Cells (2019)
• Salivary Gland Function, Development, and Regeneration — PMC / Physiological Reviews (2022)
• A Systematic Review of Methods to Diagnose Oral Dryness and Salivary Gland Function — PMC
• Sialometry and Sialochemistry: Diagnostic Tools for Sjögren's Syndrome — PMC
• Evaluation of the Concordance of Sialometry and Salivary Gland Scintigraphy in Dry Mouth Patients — PMC
• Evaluation of Salivary Diagnostics: Applications, Benefits, Challenges, and Future Prospects — PMC (2025)
• Salivary Gland Diseases: A Retrospective Clinicopathological Study of 159 Cases — PMC
• Sialolithiasis — StatPearls, NCBI Bookshelf (NIH)
• Parotid Cancer — StatPearls, NCBI Bookshelf (NIH)
• Imaging of Salivary Gland Tumours — PMC / NIH
• Incidence Rates of Salivary Gland Tumors — PubMed
• A Retrospective Study of Nonneoplastic and Neoplastic Disorders of the Salivary Glands — PMC
• The Relationship Between Dehydration and Parotid Salivary Gland Function — PubMed
• Zn²⁺ Stimulates Salivary Secretions via Metabotropic Zinc Receptor ZnR/GPR39 — Scientific Reports (2019)
• A Review of the Role of Natural Products as Treatment Approaches for Xerostomia — PMC (2023)
• Comparison of the Effect of Ginger and Aloe Vera Mouthwashes on Xerostomia in Patients with Type 2 Diabetes — PMC
• Herbal Medicine for Xerostomia in Cancer Patients: A Systematic Review of Randomized Controlled Trials — PubMed
• A Randomised Double-Blind Placebo-Controlled Clinical Trial of Fish Oil (Omega-3) in Sjögren's Syndrome Patients — PMC (2025)
• Acupuncture for Patients with Cancer-Induced Xerostomia: A Systematic Review Protocol — PMC
• Efficacy of Acupuncture in Managing Radiation-Induced Xerostomia: An Updated Meta-Analysis — Journal of Medical Sciences (2025)
• Nonpharmacological Interventions in the Management of Xerostomia: A Review — MDPI (2024)
• Effects of Chinese Herbs on Salivary Fluid Secretion by Isolated and Perfused Rat Submandibular Glands — PMC
• Regulation of Salivary Gland Function by Autonomic Nerves — Autonomic Neuroscience (2007)
• CCL28: A Promising Biomarker for Assessing Salivary Gland Functionality — PMC (2024)
• Development of a Digital Sialometry Device for Minor Salivary Glands — PMC (2025)
• Salivary Gland Diseases in Children — PMC
• Neuroanatomy, Parasympathetic Nervous System — StatPearls, NCBI Bookshelf (NIH)