Medical University of South Carolina/SC-Geriatric Education Center Oral Physiology MSc Students 2012-2013

Medical University of South Carolina/SC-Geriatric Education CenterMedical University of South Carolina/SC-Geriatric Education Center

Oral Physiology

MSc Students

2012-2013

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


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


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.


Anatomical Features of the Mouth

• Alveolar processes of the mandible and maxilla and teeth

• Tongue

• Salivary glands


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


Physiology of Teeth

• Mineral and vitamin requirements for maintenance:– Calcium– Phosphorous– Vitamin D– Vitamin C

• Decay / Cavities or Caries


Tongue

• Muscular organ

• Functions in:– Chewing– Swallowing– Speech– Site of sensory reception:

• Taste • Touch• Pain / Temperature


Papillae1

Sites of Taste Buds• Classified by

shape:– circumvallate

– foliate

– fungiform

– filiform - non-gustatory


Taste Buds1,2

• Microscopic• Contained in and

on papillae• Different types of

cells perform different functions

• Also found elsewhere in mouth


Innervations of the Tongue1,2

• Innervations by:– Chorda tympani

(cranial nerve VII)– Glossopharyngeal

(cranial nerve IX)

• Loss of innervation results in loss of sensation.


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.


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.


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


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


Functions of the Mouth

• Articulation

• Digestion– Mechanical– Chemical

• Mastication

• Swallowing


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


Saliva5

• Moistens and lubricates

• Salivary amylase

• Bacteriostatic properties

• Maintenance of homeostasis on dental surfaces:– Dissolves and dilutes metabolites– Maintains proper pH balance– Reduces plaque


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.


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


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


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.


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


Taste Mechanisms -Salty and Sour15

• Salt ions directly enter receptor cells

• Affect membrane depolarization

• Calcium entry

• Release of transmitter substance


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

Documents

Medical University of South Carolina/SC-Geriatric Education Center Oral Physiology MSc Students 2012-2013