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

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

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

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.

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

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

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

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

Medical University of South Carolina/SC-Geriatric Education Center Papillae 1 Sites of Taste Buds Classified by shape: –circumvallate –foliate –fungiform –filiform - non- gustatory

Medical University of South Carolina/SC-Geriatric Education Center Taste Buds 1,2 Microscopic Contained in and on papillae Different types of cells perform different functions Also found elsewhere in mouth

Medical University of South Carolina/SC-Geriatric Education Center Innervations of the Tongue 1,2 Innervations by: –Chorda tympani (cranial nerve VII) –Glossopharyngeal (cranial nerve IX) Loss of innervation results in loss of sensation.

Medical University of South Carolina/SC-Geriatric Education Center Taste Maps 3, 4 Taste buds are organized by region. But each region may contain several types of taste buds. Classic taste maps are an oversimplification.

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.

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: –Stensens duct - parotid –Whartons duct - submandibular –Numerous small ducts of Sublingual glands

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

Medical University of South Carolina/SC-Geriatric Education Center Functions of the Mouth Articulation Digestion –Mechanical –Chemical Mastication Swallowing

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

Medical University of South Carolina/SC-Geriatric Education Center Saliva 5 Moistens and lubricates Salivary amylase Bacteriostatic properties Maintenance of homeostasis on dental surfaces: –Dissolves and dilutes metabolites –Maintains proper pH balance –Reduces plaque

Medical University of South Carolina/SC-Geriatric Education Center Saliva and Plaque 6 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.

Medical University of South Carolina/SC-Geriatric Education Center Taste 7 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

Medical University of South Carolina/SC-Geriatric Education Center Taste Reception 8,9 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

Medical University of South Carolina/SC-Geriatric Education Center Taste Mechanisms-Sweet 10,11 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.

Medical University of South Carolina/SC-Geriatric Education Center Taste Mechanisms-Bitter 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

Medical University of South Carolina/SC-Geriatric Education Center Taste Mechanisms - Salty and Sour 15 Salt ions directly enter receptor cells Affect membrane depolarization Calcium entry Release of transmitter substance

Medical University of South Carolina/SC-Geriatric Education Center Taste Mechanisms - Umami 15 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