COMPOSITION, FUNCTIONS AND PHYSIOLOGICAL ASPECTS OF SALIVA BY ;- DR QAZI IMTIAZ RASOOL

OBJECTIVES 1. Describe the secreto-motor nerve supply of the salivary glands 2. Discuss the composition of salivary secretion. 3. Describe the mechanism and regulation of salivary secretion 4. Enumerate the functions of saliva

CLASSIFICATION OF SALIVARY GLANDS 1. ANATOMY;- 1. Major salivary glands 1)Parotid;- 20 grams, serous (20-25%) 2)Submandibular;- 10 gram mixed (70%) 3)Sublingual;-5gram mucus (5-10%) 2.Minor salivary gland 1. Not found in gingiva and anterior part of the hard palate 2.Von Ebner below the sulci of the circumvallate and folliate papillae of the tongue 3.Glands of Blandin-Nuhn: ventral tongue 4.Palatine, glossopalatine glands 5.Weber glands

2. PHYSIOLOGY;- 1.Serous salivary glands 2.Mucous salivary glands 3.Mixed salivary glands Nerve supply 1.No direct inhibitory innervation 2. Both parasympathetic (more prevalent) and sympathetic impulses 3.Parasympathetic impulses may occur in isolation, evoke most of the fluid to be excreted, cause exocytosis, induce contraction of myoepithelial cells (sympathetic too) and cause vasodilatation.

Lesser petrosal N. 9th Inferior salivary nucleus Glossopharyngeal nerve Tympanic branch Tympanic plexus Lesser petrosal nerve Otic ganglion 2-Sympath.Fs. : plexus of nerves around external carotid artery. 3-Sensory Fs. : auriculotemporal N. (branch of mandibular N.) ascends from upper end of parotid gland

Nerve supply : 2-Symp.Fs. : from plexus of nerves around Facial +Lingual arteries. 3-Sensory : lingual N. sup.salivary.N Facial N chorda tympani N lingual N submandibular ganglion lingual N

SECONDARY FACTOR 1.Para-sympathetic Nerve- moderately dilate-blood vessels 2. Salivation itself directly dilates B.V, 3.. Also vasodilator effect is caused by kallikrein secreted by activated salivary cells, Acts on α 2 -globulin Bradykinin (vasodilator)

Chemical composition and functions of saliva COMPOSITION % water 1-2L/day, ( 1ml / gm/ min - 60 times that of pancreas ). Basal flow rate 0.5→ 5mL/min pH slightly acidic (pH )- Hypo-osmotic

Solid Composition 0.5%-1% 1. Inorganic salts (1/3) Na + 40, K + 15, Cl – 25, PO 4, HCO 3 – 30(mmol/L) 2. Digestive enzyme S.Amylase, lingual lipase, 3. Proteins – Mucin, Lysozyme, Defensins, and IgA, RNA-ease Statherins,Proline-richProteins,Histatins, Cystatins, 4. Metabolic wastes – urea, uric acid 5. Hormones – Kallikaren, Lactoferrin, Somatostatin,Glucogan, Lactoperioxidase, Salivary peroxidase 6. Heavy metals- Hg, Pb 7. Nerve growth factors, renin 8. Specific blood groups A,B,O, Le secretors 9. Cellular component Desquameted Ep; cells, WBC,

Major salivary components Mucin 1 (MG1) IgA Mucin 2 (MG2) Lactoferrin Peroxidases Amylases Carbonic anhydrases Proline-rich proteins Lysozyme Statherins Histatins Size (kDa)

Formation and Secretion of Saliva 2 stage hypothesis 1.Primary saliva 1.Serous and mucous cells 2.Intercalated ducts 2.Modified saliva 1.Striated and terminal ducts 2.End product is hypotonic

Modified saliva /Secondary/Ductal secretion

Effects of Stimulation -potency of stimuli= sour>salt>sweat>bitter Lemon combinig sour+sweet is the strongest Dry>moist, round objects>irregular ResponsesParasympatheticSympathetic Saliva outputCopiousScant Response SustainedTransient Composition Protein poor ↑ K + and HCO 3 high Protein-rich, ↓ K and HCO 3 Response to denervation ↓ secretion atrophy ↓ secretion

Functions of Saliva 1. MUCIN FUNCTIONS ( mol ;- amphoteric properties buffering of acid+alkalies) 1. Lubrication Tissue Protective coating for hard and soft tissues i.e., oral cavity and esophagus, and food basically never directly touches the epithelial cells of those tissues 2. Binding mucus binds masticated food into bolus that slides easily through esophagus without inflicting damage to the mucosa. 3. Moistens food 4. Dilutes hot and irritant substances 5. React with bacterial adhesins Mucin-coated bacteria may be unable to attach to surface Bacterial adhesion, thereby blocking them

2. DIGESTION 1. α -Amylase breaks down starch amylose, amylopectin,,glucose into smaller molecules (pH 6.8) - stops functioning at pH 1.5 (stomach) 2. Lingual Lipase Secreted ( von Ebner’s glands of tongue ) Hydrolyzes medium- to long-chain triglycerides Important in digestion of milk fat in new- born highly hydrophobic enters fat globules 3. Maltase converts maltose to glucose

3. SOLUBILIZES DRY FOOD in order to be tasted, the molecules in food must be solu bilized 4. DEHYDRATION Good messenger,mouth dryness sensation of thirst. 5.PRECIPITATION OR CRYSTALLIZATION 1.Statherins prevent precipitation of CaPO 4 (TARTAR) 2. Proline-rich Proteins (PRPs) Inhibitors of CaPO 4 crystal growth (initially formed enamel )

7. ANTI-FUNGAL ACTIVITIES 1. Histatins -A group of small histidine-rich proteins Potent inhibitors of Candida albicans growth 2. Cystatins A. inhibitors of cysteine-proteases protective ( against unwanted proteolysis (bacterial proteases, lysed WBC) B. inhibit proteases in periodontal tissues effect on CaPO 4 precipitation 6. EXCRETORY FUNCTION 1.Certain waste matter such as urea + K + - thiocynate 2. Drugs iodide, pencillin, alcohol 3.Viruses;- Rabies, hepatitis, Mumps. Polio viruses.

8.ANTI-MICROBIAL ACTIVITIES Inhibition of bacterial adhesion to tooth surfaces Inhibition of glucose uptake and acid production 1. Lysozyme ;- derived 1. Major and 2. Minor salivary glands, 3. Phagocytic cells and 4.Gingival crevicular fluid 2. Sialoperoxidase (SP, salivary peroxidase) Readily adsorbed to various surfaces of mouth enamel, salivary sediment, bacteria, dental plaque 3. Myeloperoxidase (MP) From WBC entering via gingival crevice 15-20% of total peroxidase in whole saliva

9. PROTEOLYTIC ENZYMES Thiocyanate and Lactoferrin ions — lysozyme— (a) attack the bacteria, (b) aid the thiocyanate ions in entering the bacteria where these ions in turn become bactericidal, and (c) digest food particles, thus helping further to remove the bacterial metabolic support. protein antibodies that can destroy oral bacteria

– 10. PROTECTIVE EFFECT – 1. keeps the mouth and teeth clean – 2. Ig A and lysozymes (defense against bacteria) – 3. HCO 3 - prevents dental carries – 4.Diluting noxious substances and the corrosive HCL+ pepsin → esophagus and mouth during vomitting MECHANICAL FUNCTION. 1. For taste sensation, by dissolving them. 2. Assistance in chewing and swallowing(↓ resistance for slippage) 3. It helps for speech 4. It helps for washing away the food particles mouth clean 5. Sensory analysis by touch, temperature,+ taste receptors 6.Salivary epidermal growth factor promotes the healing of wounds. Animals instinctively lick their wounds

Regulation of Saliva Secretion 1.Cephalic (reflex) phase: few minutes prior to food entry 2.Gastric phase: after food enters the stomach 3.Intestinal phase: a) brief stimulatory effect as partially food enters the duodenum, b) followed by inhibitory effects (enterogastric reflex and enterogastrones)

Mechanism of Secretion is reflex action---- reflex pathway which will consist of;- 1) Sensory pathway from tongue. ( taste, touch, temperature etc 2) Superior and Inferior Salivary centre in brain. 3) Motor pathway (parasympathetic and sympathetic). 1. Conditional Reflex which is developed by habit as follows reflex from higher cortical centres a.By sight b.By smell c.Even by sound d.Thought 2. Unconditional Reflex i.e., mouth, Oesophagus, stomach, ileum.

Clinical Considerations 1.Obstruction ( Calculus formation ) 2.Role of drugs 3.Systemic disorders (Sjögren syndrome ) 4.Bacterial or viral infections (Mumps) 5.Therapeutic radiation 6.Formation of plaque and calculus

SUMMARY Salivary Families Anti- Bacterial Buffering Digestion Mineral- ization Lubricat- ion &Visco- elasticity Tissue Coating Anti- Fungal Anti- Viral Carbonic anhydrases, Histatins Amylases, Mucins, Lipase Cystatins, Histatins, Proline- rich proteins, Statherins Mucins, Statherins Amylases, Cystatins, Mucins, Proline-rich proteins, Statherins Histatins Cystatins, Mucins Amylases, Cystatins, Histatins, Mucins, Peroxidases

Today’ s thought 1.The modern day chewing gums are made of four major ingredients including synthetic rubber, plastic, sugar, and coloring (dye). 2.Instead of telling customers what they are really eating, ‘gum base’ is used to generalize a list of ingredients that is never published 3.Most chewing gum is sweetened with aspartame. Long term use of aspartame has been linked with cancer, diabetes, neurological disorders, and birth defects 4.You are using 8 muscles during chewing, over use of jaw joint causing unnecessary tears in cartilages 5.Wastage of 6 glands secretions, more intake of sugars, allergy