Saliva production or salivation occurs in the oral cavity by the numerous minor salivary glands in the oral mucosa and three major salivary glands also located in the oral cavity. Since saliva, in addition to its physical functions, also performs important biochemical tasks with regard to digestive initiation (sugar), defense against infection and relief of pain sensations, saliva production in the optimal quantity and composition is enormously important. Controlled is saliva production by the autonomic nervous system.
What is salivation?
Saliva production, or salivation, occurs in the oral cavity by the numerous minor salivary glands in the oral mucosa and three major salivary glands also located in the oral cavity. Saliva production and secretion into the oral cavity occurs in the approximately 600 to 1,000 “minor salivary glands” (glandulae salivariae minores) distributed in the oral mucosa, which are counted among the palatal glands, and the three “major salivary glands”, which are each located in pairs: the parotid gland (glandula parotis), the submandibular gland (glandula submandibularis) and the sublingual gland (glandula sublingualis). Although oral saliva consists of 95% water and only 0.5% solutes, the substances dissolved in saliva are contributed by the individual salivary glands in varying concentrations and compositions, so it is important that all salivary glands are functional and can contribute to the optimal amount and composition of saliva. The minor salivary glands produce a mucilaginous secretion, especially in the area of the soft palate and uvula, while the fluid secreted by the paired parotid gland consists of an aqueous solution in which proteins and enzymes (especially amylase to break down certain carbohydrates) and immunoglobulins to defend against infection are dissolved. Numerous electrolytes and minerals such as magnesium, potassium, calcium, iron and many others are also detectable in saliva. The mandibular salivary glands, which are also paired, produce (secrete) the bulk of oral saliva. They are seromucous glands that contribute enzymes and proteins as well as mucous secretions. The secretion of the sublingual glands is purely mucosal, consisting of thick saliva.
Function and task
The main task and function of salivary production is to provide saliva in the optimal amount and composition at the optimal time in the oral cavity. On average, the salivary glands produce 0.5 to about 1.5 liters of saliva daily. Even if no food is consumed, a basic quantity of about 0.5 liters is secreted. On the one hand, the saliva itself ensures that processes such as swallowing, speaking, tasting and smelling are possible due to its mucus content; on the other hand, saliva prevents infections due to its content of endogenous antibacterial and antifungal enzymes and hormones. Digestive enzymes such as amylases already initiate the breakdown of carbohydrates. The slightly alkaline character of saliva in combination with traces of fluoride and rhodanide reduces the risk of caries and contributes to the preservation of tooth enamel. Opiorphins, the body’s own opioid painkilling substances, have also been detected in saliva. In part, the body uses saliva production to flush waste or harmless substances out of the body through the lymphatic system. Particular emotional situations such as stress, joy, anger and fear can be detected in saliva via the concentration of certain hormones. For example, cortisol levels in saliva rise sharply during stressful situations. Steroid hormones – including sex hormones – can also be detected in saliva. For example, kissing during sexual arousal can have a stimulating effect on the partner, as small amounts of sex hormones are mutually transferred. A self-reinforcing control loop occurs if the process is not consciously aborted by either partner.
Diseases and ailments
The main complaints related to saliva production may be overproduction or underproduction of saliva. In principle, this may be due to malfunction or disease of the glands themselves, or it may be caused by signals from the autonomic nervous system that are too weak or too strong. Overproduction of saliva (hypersalivation) can have many causes.Pathologically increased saliva production often occurs in connection with neurological diseases such as Parkinson’s disease and amyotrophic lateral sclerosis (ALS). Diseases such as schizophrenia and manic depression are also usually accompanied by disorders of saliva production. Increased salivation is listed as a side effect for a variety of medications. Toxic substances associated with parasympathetic disorders can cause a similar effect. Insufficient saliva production (hyposialia) can be caused by fluid deficiency, by specific diseases such as Sjögren’s syndrome, by medications, or by radiation to the head. Hyposialia is noticeable by unpleasant dry mouth (xerostomia). Impaired saliva production can also be the result of a direct bacterial or viral disease of the salivary glands, such as mumps, or the result of inflammation of the glands. Likewise, underlying diseases such as acquired immunodeficiency (e.g., AIDS), elevated blood glucose levels, and hormonal imbalances can also have an effect. In rare cases, the outflow of saliva from the glands may be obstructed due to salivary stones. Salivary stones usually form from calcium apatite. Protein and vitamin deficiencies, alcohol and nicotine abuse also affect impaired saliva production. Tumors can form particularly in the parotid glands, although in about three-quarters of cases they are benign. Typically, the tumors grow slowly and initially cause only minor symptoms. The rarer tumors, in either of the mandibular salivary glands or in one or more of the minor salivary glands, are often malignant and are usually manifested by pain, facial nerve palsies, and visible and palpable lumps in the mouth and neck.
