[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Physiology](https://durgical.com/en/physiology/) › [Gastrointestinal](https://durgical.com/en/physiology/#s-gi) › Salivary secretion [Physiology](https://durgical.com/en/physiology/) · [Gastrointestinal](https://durgical.com/en/physiology/#s-gi) # Salivary secretion - Mechanism - For completeness The salivary glands make 1 to 1.5 L of saliva a day to moisten food, start starch digestion and protect the mouth and teeth. Updated 2026-11-01 Also called: Saliva, Salivary glands **See it in 3D:** [Parotid gland](https://durgical.com/en/anatomy/parotid-gland/) · [Submandibular gland](https://durgical.com/en/anatomy/submandibular-gland/) · [Sublingual gland](https://durgical.com/en/anatomy/sublingual-gland/) · [Tongue](https://durgical.com/en/anatomy/tongue/) ## Key points - Saliva is hypotonic to plasma, with more K⁺ and HCO₃⁻ and less Na⁺ and Cl⁻. - At higher flow there is less time for ductal modification: saliva comes closer to plasma (more Na⁺ and Cl⁻), though it stays hypotonic. - Parasympathetic (VII for submandibular and sublingual; IX for parotid via the otic ganglion): copious watery saliva. - Sympathetic: small volume, rich in protein and mucus. - Components: salivary amylase, mucins, lysozyme, lactoferrin, secretory IgA and haptocorrin (which protects vitamin B12). - Aldosterone increases Na⁺ reabsorption and K⁺ secretion in the ducts, as in the colon. ## What it is Saliva is made in two steps. Acini secrete a plasma-like fluid, and the ducts modify it: they reabsorb Na⁺ and Cl⁻ and secrete K⁺ and HCO₃⁻ while letting little water through, so the final saliva is hypotonic. Unlike almost all of the gut, both parasympathetic and sympathetic nerves stimulate it, although the parasympathetic dominates. ## How it works, step by step - Smell, taste, chewing or thinking of food activates the salivatory nuclei of the brainstem. - Acetylcholine (M3) raises Ca²⁺ in acinar cells and opens apical Cl⁻ channels. - Cl⁻ moves into the lumen, Na⁺ and water follow: an isotonic, plasma-like fluid forms. - In the ducts, the water-tight epithelium reabsorbs Na⁺ and Cl⁻ and secretes K⁺ and HCO₃⁻. - The final saliva leaves hypotonic and slightly alkaline, with a pH near 7 at high flow. - Local vasodilation (bradykinin, VIP) sustains high flow during stimulation. ## Clinical notes - Anticholinergic drugs and head and neck radiotherapy cause dry mouth (xerostomia) and more caries. - Sialolithiasis: ≈80% in the submandibular gland (thicker, more alkaline saliva and a long uphill duct); pain and swelling at meals. - Mumps: painful parotid swelling and raised serum amylase of salivary origin. - A high serum amylase is not always pancreatic: the salivary glands contribute too. ## Memory aid 'The ducts keep the salt and hand over potassium and bicarbonate': that is why saliva comes out hypotonic. ## Test yourself Think of the answer, then tap the question to see it. ## Why is saliva hypotonic even though the acini secrete an isotonic fluid? The ducts reabsorb more Na⁺ and Cl⁻ than the K⁺ and HCO₃⁻ they secrete, and their epithelium is poorly permeable to water; water does not follow the salt, so saliva ends up hypotonic. ## Why is saliva closer to plasma when flow is very high? Fluid moves through the ducts faster, leaving less time to reabsorb Na⁺ and Cl⁻; even so, saliva stays hypotonic. ## Why do most salivary stones form in the submandibular gland? Its saliva is more mucous and alkaline, with more calcium, and its duct is long and runs uphill; slow flow favours salt precipitation. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/physiology/salivary-secretion/) ## See it in 3D The structures of Durgical's 3D anatomy where it happens. - [Parotid gland](https://durgical.com/en/anatomy/parotid-gland/) - [Submandibular gland](https://durgical.com/en/anatomy/submandibular-gland/) - [Sublingual gland](https://durgical.com/en/anatomy/sublingual-gland/) - [Tongue](https://durgical.com/en/anatomy/tongue/) ## Related topics - [Carbohydrate digestion and absorption](https://durgical.com/en/physiology/carbohydrate-digestion-and-absorption/) - [Sympathetic and parasympathetic effects on each organ](https://durgical.com/en/physiology/sympathetic-and-parasympathetic-effects-on-each-organ/) - [Adrenergic and cholinergic receptors](https://durgical.com/en/physiology/adrenergic-and-cholinergic-receptors/) - [Taste and smell](https://durgical.com/en/physiology/taste-and-smell/) - [Swallowing and esophageal motility](https://durgical.com/en/physiology/swallowing-and-esophageal-motility/) ## Related conditions - [Sialolithiasis (salivary stones)](https://durgical.com/en/conditions/sialolithiasis/) - [Mumps](https://durgical.com/en/conditions/mumps/) - [Dental caries](https://durgical.com/en/conditions/dental-caries/) - [Parotid gland tumours](https://durgical.com/en/conditions/parotid-gland-tumours/) ## In Biochemistry - [Amylase as a lab test](https://durgical.com/en/biochemistry/topics/amylase-as-a-lab-test/) [← All of physiology](https://durgical.com/en/physiology/) Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given. Sources: [23.3 The Mouth, Pharynx, and Esophagus](https://openstax.org/books/anatomy-and-physiology-2e/pages/23-3-the-mouth-pharynx-and-esophagus) (OpenStax (Rice University), 2022); [Anatomy, Head and Neck, Salivary Glands](https://www.ncbi.nlm.nih.gov/books/NBK538325/) (StatPearls (NCBI Bookshelf), 2024); [Sialolithiasis](https://www.ncbi.nlm.nih.gov/books/NBK549845/) (StatPearls (NCBI Bookshelf), 2024); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 65). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/physiology/salivary-secretion/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/physiology/salivary-secretion/