Salivary Glands

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Salivary Glands:

Salivary Glands Dr Raghuveer Choudhary Associate Professor Dept. of Physiology

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Salivary secretion

The Oral Cavity:

The Oral Cavity Figure 24–6

4 Functions of the Oral Cavity:

4 Functions of the Oral Cavity Sensory analysis: of material before swallowing Mechanical processing: through actions of teeth, tongue, and palatal surfaces Lubrication: mixing with mucus and salivary gland secretions Limited digestion: of carbohydrates and lipids

The Salivary Glands:

The Salivary Glands Figure 24–7

Salivary Glands:

Salivary Glands Parotid gland Submandibular

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Sublingual Submandibular Salivary Glands

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EXTRINSIC SALIVARY GLANDS 1 – 1.5 liters of saliva /day Exocrine glands 1.PAROTID GLANDS – anterior & inferior to ear clear, watery saliva & amylase Stenson’s duct – enters opposite 2 nd upper molar MUMPS – viral inflammation & swelling

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2 . SUBMANDIBULAR GLANDS - body of mandible Secretes serous fluid – serous cells Wharton’s Ducts – open inferior to tongue near frenulum 3. SUBLINGUAL GLANDS – floor of mouth Multiple ducts posterior to submandibular duct ( Rivinus ducts) Mucous secretions – mucous cells – thick & stringy

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Secretion of saliva Salivary glands parotid submandibular sublingual buccal Saliva contains two types of protein secretion: 1. Serous secretion: contains ptyalin, which is an enzyme for digesting starches 2. mucous secretion: contains mucin, which is for lubricating and surface protective purpose Serous secretion mucous secretion Serous secretion mucous secretion

Digestive Processes occurring in the mouth, pharynx and esophagus:

13 Digestive Processes occurring in the mouth, pharynx and esophagus Within the mouth, food is chewed, mixed, and moistened with saliva which contains enzymes that aid in the process of chemical digestion Up to 99.5% of SALIVA is composed of water. It is slightly acidic and it’s solutes include electrolytes (such as sodium and potassium), salivary amylase – a digestive enzyme, mucin – which hydrates the food, and wastes such as urea.

Salivary Glands:

Salivary Glands 3 pairs secrete into oral cavity Each pair has distinctive cellular organization: and produces saliva with different properties Produce 1.0–1.5 liters of saliva each day: 70% by submandibular glands 25% by parotids 5% by sublingual glands

Digestive System:

Digestive System Secretion of Saliva (800-1500 mL /day; pH: 6.0-7.0, suitable for ptyalin; has K and bicarbonate) Salivary Glands Secretion Parotid serous Submandibular Serous and mucus Sublingual Serous and mucus Buccal mucus Serous – has ptyalin for starch digestion(thin watery secretions) Mucus – has mucin for lubrication and surface protection(viscous secretions)

Saliva:

Saliva 99.4% water 0.6% includes: electrolytes (Na + , Cl — , and HCO 3 — ) buffers glycoproteins (mucins)- Glycoproteins, responsible for lubricating action antibodies enzymes waste products

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Gland location histology % of total salivary secretion Nerve supply Parotid In front of ear Purely serous 25% 9 th cranial Nerve Sub-mandibular Sub-maxillary triangle Mixed S:M::4:1 70% 7 th cranial nerve Sub-lingual Floor of mouth Mixed S:M::1:4 5% 7 th cranial nerve

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Composition of saliva Major characteristics of saliva: - relatively large volume - high potassium concentration - low osmolarity - two stages in secretion acini x salivary duct - specialized organic materials

Composition of Saliva:

Composition of Saliva In 24 hours-1-1.5 lit. , pH=6.0 Organic compounds- salivary amylase, lingual lipase, lysozyme , mucin , IgA , Kallikerin Trace amount of urea, EDGF, NGF,Uric acid, FFA, blood group . Inorganic compounds Cations (positive ions)- Na+,k+,Ca ++(trace) Anoins (negative ions)-HCO3,Cl,Br/I

4 Functions of Saliva :

4 Functions of Saliva Lubricating the mouth Moistening and lubricating materials in the mouth Dissolving chemicals that: stimulate taste buds provide sensory information 4. Initiate digestion of: complex carbohydrates by enzyme salivary amylase (ptyalin or alpha-amylase) lipids by enzyme lingual lipase

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Functions of saliva Digestion - ptyalin (α-amylase) - identical to pancreatic amylase - cleaves α-1,4-glycosidi c bonds of carbohydrates - pH optimum 7 - functional l y replaceable by pancreatic enzyme - lingual lipase - triglycerides - lower acidic optimum – remains active throughout the stomach and into the proximal duodenum - dissolves dietary constituents - increases the sensitivity of taste buds

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Functions of saliva Lubrication - mucus content - facilitates swallowing - necessary for speech Protection - dilution and buffering of harmful substances - salivation before vomiting - xerostomia chronic infections - lysozym , IgA binding protein, lactoferin - take-up of Ca and phosphate - concentration

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Protective function • bicarbonate (neutralization of acid produced by bacteria and gastric reflux) • antibacterial ( lysozyme ) • lactoferrin (binds Fe, decreases bacterial growth) • secretory immunoglobulin ( IgA ) • epidermal growth factor • mouth hygiene • facilitates speaking Digestive function •  -amylase (= ptyalin) • lingual lipase • lubrification food for swallowing • dissolving substances for taste mechanism

Saliva:

29 Saliva The average output of saliva is 1000 – 1500 ml per day! Saliva also contains lysozyme, defensins, and IgA antibodies for protection against microorganisms. The role of saliva is to cleanse the mouth, dissolve food so it can be tasted, moisten food and aid in propulsion of food through the digestive tract, and to begin the chemical breakdown of starchy foods.

Control of Salivation :

30 Control of Salivation Salivation is controlled by the parasympathetic division (PS) of the nervous system. Humans contain receptors in their mouths which when stimulated, send signals to the pons . The PS activates cranial nerves VII (facial) and IX (glossopharyngeal) to increase saliva output. In contrast, the sympathetic division causes release of thick, mucin rich saliva. .

Control of Salivation:

31 Control of Salivation When strongly stimulated, the blood vessels serving the salivary glands constrict, which ceases release of saliva and causes drymouth. Dehydration also inhibits salivation because low blood volume results in reduced filtration pressure at capillaries

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Secretion of ions in the saliva Submandibular salivary glands: acini and salivary ducts acini ducts Salivary secretion is a two-stage operation: Acini secrete primary secretion As the primary secretion flows through the ducts, two major active transport pocesses take place to modify the ionic composition Ptyalin, mucin, ions

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Secretion of ions in the saliva 1. Na + are actively reabsorbed and K + are actively secreted in exchange for the Na + acini ducts Na + K + 2. There is excess of Na + reabsorption over K + secretion, so creates electrical negativity in the ducts, and in turn cause Cl - to be reabsorbed passively. 3. HCO 3 - are secreted into the lumen actively or by exchange of Cl - Cl - HCO 3 -

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Composition of saliva

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Anatomy, Inervation

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Composition of saliva

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Neural regulation of secretion