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Medical University of South Carolina/SC-Geriatric Education CenterMedical University of South Carolina/SC-Geriatric Education Center
Oral Physiology
MSc Students
2012-2013
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Medical University of South Carolina/SC-Geriatric Education Center
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
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Medical University of South Carolina/SC-Geriatric Education Center
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
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Medical University of South Carolina/SC-Geriatric Education Center
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.
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Medical University of South Carolina/SC-Geriatric Education Center
Anatomical Features of the Mouth
• Alveolar processes of the mandible and maxilla and teeth
• Tongue
• Salivary glands
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Medical University of South Carolina/SC-Geriatric Education Center
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
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Medical University of South Carolina/SC-Geriatric Education Center
Physiology of Teeth
• Mineral and vitamin requirements for maintenance:– Calcium– Phosphorous– Vitamin D– Vitamin C
• Decay / Cavities or Caries
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Medical University of South Carolina/SC-Geriatric Education Center
Tongue
• Muscular organ
• Functions in:– Chewing– Swallowing– Speech– Site of sensory reception:
• Taste • Touch• Pain / Temperature
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Medical University of South Carolina/SC-Geriatric Education Center
Papillae1
Sites of Taste Buds• Classified by
shape:– circumvallate
– foliate
– fungiform
– filiform - non-gustatory
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Medical University of South Carolina/SC-Geriatric Education Center
Taste Buds1,2
• Microscopic• Contained in and
on papillae• Different types of
cells perform different functions
• Also found elsewhere in mouth
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Medical University of South Carolina/SC-Geriatric Education Center
Innervations of the Tongue1,2
• Innervations by:– Chorda tympani
(cranial nerve VII)– Glossopharyngeal
(cranial nerve IX)
• Loss of innervation results in loss of sensation.
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Medical University of South Carolina/SC-Geriatric Education Center
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.
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Medical University of South Carolina/SC-Geriatric Education Center
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.
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Medical University of South Carolina/SC-Geriatric Education Center
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
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Medical University of South Carolina/SC-Geriatric Education Center
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
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Medical University of South Carolina/SC-Geriatric Education Center
Functions of the Mouth
• Articulation
• Digestion– Mechanical– Chemical
• Mastication
• Swallowing
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Medical University of South Carolina/SC-Geriatric Education Center
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
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Medical University of South Carolina/SC-Geriatric Education Center
Saliva5
• Moistens and lubricates
• Salivary amylase
• Bacteriostatic properties
• Maintenance of homeostasis on dental surfaces:– Dissolves and dilutes metabolites– Maintains proper pH balance– Reduces plaque
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Medical University of South Carolina/SC-Geriatric Education Center
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.
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Medical University of South Carolina/SC-Geriatric Education Center
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
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Medical University of South Carolina/SC-Geriatric Education Center
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
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Medical University of South Carolina/SC-Geriatric Education Center
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.
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Medical University of South Carolina/SC-Geriatric Education Center
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
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Medical University of South Carolina/SC-Geriatric Education Center
Taste Mechanisms -Salty and Sour15
• Salt ions directly enter receptor cells
• Affect membrane depolarization
• Calcium entry
• Release of transmitter substance
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Medical University of South Carolina/SC-Geriatric Education Center
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