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Lect 2. (mouth and salivary glands)

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GIT 2

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Lect 2. (mouth and salivary glands)

  1. 1. • Mouth or buccal cavity. • It is formed by cheeks, lips and palate. • Inside mouth are the teeth, tongue and salivary glands. • Mouth opens anteriorly to the exterior through lips. • Mouth opens Posteriorly through fauces into the pharynx. • Digestive juice present in the mouth is saliva, which is secreted by the
  2. 2. FUNCTIONS OF MOUTH: 1. Ingestion of food materials 2. Chewing the food and mixing it with saliva 3. Appreciation of taste of the food 4. Transfer of food (bolus) to the esophagus by swallowing. 5 . R o l e i n s p e e c h 6 . S o c i a l f u n c t i o n s s u c h a s s m i l i n g a n d o t h e r e x p r e s s i o n s .
  3. 3. SALIVARY GLANDS: MAJOR GLANDS ARE: 1. Parotid glands. 2. Submaxillary or submandibular glands 3. Sublingual glands. MINOR SALIVARY GLANDS ARE: 1. Lingual Mucus Glands 2. Lingual Serous Glands 3. Buccal Glands 4. Labial Glands 5. Palatal Glands
  4. 4. CLASSIFICATION OF SALIVARY GLANDS: 1. Serous Glands: • mainly made up of serous cells secrete (watery saliva). • Parotid glands and lingual serous glands are the serous glands. 2. Mucus Glands: • mainly made up of mucus cells secrete (thick, viscous saliva with high mucin content). • Lingual mucus glands, buccal glands and palatal glands. 3. Mixed Glands: • made up of both serous and mucus cells. • Submandibular, sublingual and labial glands.
  5. 5. GLANDS:
  6. 6. PROPERTIES AND COMPOSITION OF SALIVA: 1. Volume: 1000 mL to 1500 mL of saliva is secreted per day. 2. Reaction: Mixed saliva from all the glands is slightly acidic with pH of 6.35 to 6.85 3. Specific gravity: It ranges between 1.002 and 1.012 4. Tonicity: Saliva is hypotonic to plasma. • Mixed saliva contains 99.5% water and 0.5% solids.
  7. 7. 1. Preparation of food for swallowing. 2. Appreciation of taste. 3. Digestive function. (Amylase, maltase, lingual lipase). 4. Cleansing and protective functions (proline-rich proteins). 5. ROLE IN SPEECH. 6. EXCRETORY FUNCTION. 7. REGULATION OF BODY TEMPERATURE. 8. REGULATION OF WATER BALANCE.
  8. 8. Production of saliva:
  9. 9. REGULATION OF SALIVARY SECRETION: Function of Parasympathetic Fibers: 1. Stimulation of parasympathetic fibers of salivary glands causes secretion of saliva with large quantity of water. 2. activate the acinar cells and cause vasodilation. 3. The neurotransmitter is acetylcholine. Function of Sympathetic Fibers: 1. Stimulation of sympathetic fibers causes secretion of saliva, which is thick and rich in organic constituents. 2. activate the acinar cells and cause vasoconstriction. 3. The neurotransmitter is noradrenaline.
  10. 10. REFLEX REGULATION OF SALIVARY SECRETION: 1. Unconditioned Reflex:  Inborn reflex.  Not need any previous experience.  Any substance placed in the mouth will secrete saliva. 2. Conditioned Reflex:  Acquired.  Needs previous experience.  Presence of food in the mouth is not necessary.  The stimuli for this reflex are the sight, smell, hearing or thought of food.
  11. 11. EFFECT OF DRUGS AND CHEMICALS ON SALIVARY SECRETION: • Substances which increase salivary secretion 1. Sympathomimetic drugs like adrenaline and ephedrine. 2. Parasympathomimetic drugs like acetylcholine, pilocarpine, muscarine and physostigmine. 3. Histamine. • Substances which decrease salivary secretion 1. Sympathetic depressants like ergotamine and dibenamine. 2. Parasympathetic depressants like atropine and scopolamine. 3. Anesthetics such as chloroform and ether stimulate the secretion of saliva. However, deep anesthesia decreases the secretion due to central inhibition.

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