Saliva Dr. Wasif Haq

Introduction The clear slightly acidic muco-serous secretion formed by salivary glands. pH of saliva : Significance of weakly acidic pH? Daily secretion (volume) ml averagely. Secreted by major & minor salivary glands.

Why Do We Need Saliva? Required for well being of mouth. People having deficient saliva have difficulty in eating, swallowing, speaking, taste perception, have more chances of mucosal injuries, ulcerations and dental caries (tooth decay).

Functions of Saliva A. Role in Digestion: Water & Mucin protein: Lubrication & moistening food substances to form bolus, easy swallowing. Amylase/Ptyalin & Lipase: Amylase/ Ptyalin: Initial digestion of starch. Lipase: Initial digestion of Triglycerides.

Functions of Saliva B. Antimicrobial action Thiocynate ions & lysozyme system, antibodies that kill bacteria and prevent bacterial adherence to oral tissues.

Functions of Saliva C. Taste facilitation: By making food substances soluble, saliva convey taste molecules to taste receptors, thereby helping in taste facilitation.

Functions of Saliva D. Protection: Saliva has washing, diluting effect that helps to clear food substances especially sugars from oral cavity, preventing tooth decay by bacteria. Mucin forms protective barrier against bacterial toxins, minor trauma and minimizes friction amongst tissues.

Functions of Saliva E. Buffering action Bicarbonate & Phosphate ions maintain constant pH, preventing acidic shift of pH, help protect tooth decay. Metabolism of salivary proteins by bacteria produces Urea & Ammonia that increases pH.

Functions of Saliva F. Teeth protection: Saliva is super saturated with Calcium & Phosphate that protect against mineral loss from tooth substance. Fluoride which is caries resistant. Contain antibodies that prevent bacterial attachment.

Composition of Saliva Parotid gland: Serous secretion (Containing large quantities of Ptyalin for starch digestion) Submandibular & sublingual gland: Mixed secretion (Mucous + Serous). Mucin protein has lubricative & protective function. Minor salivary glands: Purely mucous secretion.

Composition of Saliva

Structure of Salivary Glands Salivary glands comprise of (a) Parenchyma (Acini and ducts) (b) Stroma (Nerves & blood vessels) Acini : Terminal secretory unity of salivary glands. Ducts: Where acini open, ducts convey saliva to oral cavity.

Formation of Saliva Acini form “primary secretion”, isotonic, similar to plasma composition. Ducts modify primary secretion, thereby producing ‘secondary secretion’, hypotonic. Saliva contains greater quantity of K + and HC0 3 - ions while lesser quantity of Na + and Cl - ions. In secondary secretion, Na + reabsorbed, K + secreted in excess, creation of electrical negativity (-70mv) causing Cl - reabsorption passively followed by substitution by HC0 3 - ions.

Formation of Saliva Final saliva secretion comprises of small quantities of Na + and Cl - (1/7 th -1/10 th of plasma levels). In rapid stimulation of saliva, less modification of saliva takes place by ducts. Therefore lesser Na + and Cl - reabsorption will take place, composition similar to plasma levels. Effect of Aldosterone: “Sodium conserving hormone”. When released, more Na + and Cl - reabsorption from saliva, reducing concentration to almost zero in saliva. K + levels rise 7 times greater than normal saliva.

Regulation of Saliva Superior & inferior salivatory nuclei in brainstem (midbrain, pons, medulla). Parasympathetic and sympathetic nervous system stimulates, former has greater effect.

Regulation of Saliva Increase salivaDecrease Saliva 1. Parasympathetic ++& sympathetic nervous system 1.Dehydration 2. Vasodilatation of salivary blood vessels by Parasympathetic nervous system through Kallikrien protein that forms Bradykinin; a vasodilator. 2.Fear 3. Smell of good food.3.Sleep 4. Nausea/ Vomiting (Protective function) 4.Rough objects in mouth 5. Tactile sensation of oral mucosa, tongue. 5.Certain medications. 6. Thinking about good food( appetite center in brain) ---