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Oral Physiology

Oral Physiology. MSc Students 2012-2013. The Mouth or Oral Cavity. Common entrance to the digestive and respiratory tracts Site for entry of foodstuffs Initial processing of food called mastication Articulation of speech Alternate airway. Anatomy of the Mouth.

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Oral Physiology

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  1. Oral Physiology MSc Students 2012-2013

  2. The Mouth or Oral Cavity • Common entrance to the digestive and respiratory tracts • Site for entry of foodstuffs • Initial processing of food called mastication • Articulation of speech • Alternate airway

  3. Anatomy of the Mouth • Delimited anteriorly by the lips and posteriorly by the anterior tonsillar pillars • The roof of the mouth is formed by the hard and soft palates • The floor of the mouth is formed by the tongue • The walls are lined by the buccal mucosa

  4. Division of the Mouth • The mouth is divided into two cavities by the teeth. • The vestibule is between teeth and cheeks. • The outside surface of the teeth is the buccal surface. • The oral cavity is internal to the teeth. • The inside surface of the teeth is the lingual surface.

  5. Anatomical Features of the Mouth • Alveolar processes of the mandible and maxilla and teeth • Tongue • Salivary glands

  6. Teeth and Alveolar Processes • Calcified, enamel – hardest substance in body • Embedded in bony sockets of alveolar processes • Humans have two sets: • Deciduous - “milk” or “baby” teeth • Permanent

  7. Physiology of Teeth • Mineral and vitamin requirements for maintenance: • Calcium • Phosphorous • Vitamin D • Vitamin C • Decay / Cavities or Caries

  8. Tongue • Muscular organ • Functions in: • Chewing • Swallowing • Speech • Site of sensory reception: • Taste • Touch • Pain / Temperature

  9. Classified by shape: circumvallate foliate fungiform filiform - non-gustatory Papillae1 Sites of Taste Buds

  10. Taste Buds1,2 • Microscopic • Contained in and on papillae • Different types of cells perform different functions • Also found elsewhere in mouth

  11. Innervations of the Tongue1,2 • Innervations by: • Chorda tympani (cranial nerve VII) • Glossopharyngeal (cranial nerve IX) • Loss of innervation results in loss of sensation.

  12. Taste Maps3, 4 • Taste buds are organized by region. • But each region may contain several types of taste buds. • Classic taste maps are an oversimplification.

  13. Salivary Glands • Major and Minor Salivary Glands • Produce and secrete saliva • Three pairs of major glands: • Parotid • Submaxillary • Sublingual • Over 1000 minor glands • Buccal, palatal, lingual Illustration adapted by Doug Greene from various sources.

  14. Major Salivary Glands • Parotid – below and anterior to the ear • Submandibular – below the mandible • Sublingual – anterior floor of the mouth • Orifices / ducts: • Stensen’s duct - parotid • Wharton’s duct - submandibular • Numerous small ducts of Sublingual glands

  15. Minor Salivary Glands • Numerous - can be > 1,000 • Microscopic • Scattered • Buccal - inside of lips and cheeks • Palatal - roof of mouth • Lingual - tongue, around circumvalate papillae • Not all in mouth proper, also in the larynx and epiglottis

  16. Functions of the Mouth • Articulation • Digestion • Mechanical • Chemical • Mastication • Swallowing

  17. Salivary Gland Function • Innervation by both sympathetic and parasympathetic divisions of the autonomic nervous system. • Saliva production affected by: • Chewing • Taste, smell or even thought of food • Emotions like fear, anxiety and mental effort • Dehydration • Sleep

  18. Saliva5 • Moistens and lubricates • Salivary amylase • Bacteriostatic properties • Maintenance of homeostasis on dental surfaces: • Dissolves and dilutes metabolites • Maintains proper pH balance • Reduces plaque

  19. Saliva and Plaque6 • Enamel is hardest tissue in the body formed only before tooth eruption. • May be dissolved by acids from foods or produced by bacteria resulting in caries. • Saliva washes away microbes. • Saliva neutralizes acids or bicarbonate.

  20. Taste7 • Fine Taste vs. Crude Taste • Five flavors: • Sweet • Salty • Sour • Bitter • Umami • Non-conventional taste stimuli such as fatty acids, metals or other minerals • Trigeminal sense like heat or mouth feel

  21. Taste Reception8,9 • Different taste molecules or tastants received differently • Different taste buds sensitive to more than one type of tastant • Probably considerable overlap among different taste buds

  22. Taste Mechanisms-Sweet10,11 • Membrane receptor binds tastant. • cAMP levels elevated by second messenger. • PKA-mediated phosphorylation of K+ channels. • Membrane depolarization allows Ca ++ entry. • Gustducin activation in receptor cell transmitter to basal cells. • Transmitter substance released by receptor cell via basal cells initiates nervous signals to brain.

  23. Taste Mechanisms-Bitter12-14 • Tastant binding affects different second messenger – IP3 • Internal Ca ++ stores initiate release of transmitter substance • Similar pattern of gustducin activation • Many bitter or alkaline substances poisonous

  24. Taste Mechanisms -Salty and Sour15 • Salt ions directly enter receptor cells • Affect membrane depolarization • Calcium entry • Release of transmitter substance

  25. Taste Mechanisms - Umami15 • Response to certain amino acids such as glutamate, aspartate and related compounds • First identified in Japan • Metabotropic glutamate receptor (mGluR4) mediates umami taste • Binding to the receptor activates a G-protein elevating intracellular Ca2+ • Monosodium glutamate may stimulate the umami receptors • Additional ionotropic glutamate receptors (NMDA-receptor) also present

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