Ch. 9 Physiology of Mastication and Deglutition

1. Ch. 9Physiology of Mastication and Deglutition

2. Introductory Terms • Dysphagia: A disorder of swallowing • Bolus: ball of food or liquid to be swallowed • Mastication: the process of preparing food for swallowing • Moving food onto the grinding surfaces of the teeth • Chewing • mixing it with saliva in preparation for swallowing • Deglutition: the process of swallowing • Both the two above concepts require integration of lingual, velar, pharyngeal, facial muscle movement, laryngeal adjustments, respiratory control

3. Introductory Terms • Perioral region: around the mouth • Rooting Reflex: reflexive response of infant to tactile stimulation of the cheek or lips, infant turns toward stimulus, opens mouth • Sucking Reflex: tongue protrusion and retraction in preparation for receipt of liquid; stimulated by contact to the upper lip • Esophageal Reflux: esophageal regurgitation into the hypopharynx • Nasal regurgitation: loss of food or liquid through the nose • Peristaltic: Wavelike

4. Introductory Terms • Oral Transit Time: time required to move the bolus to the point of initiation of the pharyngeal stage of swallowing • Pharyngeal Transit Time: time required to move the bolus from the beginning of pharyngeal swallow to the time the bolus enters the esophagus

5. Organizational Patterns • Oral Preparatory Stage • Stage in which food is prepared for swallow • Oral Stage • Bolus transmitted to pharynx • Pharyngeal Stage • Bolus transmitted to the esophagus • Numerous physiological responses • Esophageal Stage • Food is transported from the upper esophageal region to the stomach

6. Deficit Patterns • Oral Preparatory Stage • Neuromuscular deficits • Loss of sensation and awareness • Weak buccal musculature • Weak muscles of mastication may cause inadequqtely chewed food • Weak lingual muscles may cause poor mixture of saliva with food, inadequate bolus production, difficulty compressing bolus onto hard palate • Weak soft palate muscles may cause the velum to not be fully depressed, tongue not adequately elevated in back, permitting food to escape into the pharynx prior to initiation of pharyngeal reflexes • Food entering pharynx prior to a reflexive response may reach the open airway and produce an aspiration pneumonia

7. Deficit Patterns • Oral Stage • Sensory and Motor dysfunction • Weakened movements cause reduced oral transit time, fodd may remain on tongue and hard palate following transit • Epiglottis fail to invert over laryngeal opening, limited elevation of the hyoid, may be increased pooling of food or liquid in the valleculae • Difficulty initiating a reflexive swallow may be due to a sensory deficit

8. Deficit Patterns • Pharyngeal Stage • Sensory and Motor Dysfunction • Slow velar elevation may result in nasal regurgitation • Reduced sensation of fauces, posterior tongue, pharyngeal wall, soft palate may cause elevated threshold for trigger of swallowing reflex • Reduced function of pharyngeal constrictors may result in slowed pharyngeal transit time of bolus and individual may reinitiate respiration • Weakened pharyngeal function may result in residue left in the valleculae • Failure of the hyoid and thyroid to elevate may result in loss of airway protection, food may fall into larynx and be aspirated on breathing

9. Deficit Patterns • Esophageal Stage • GERD: acids from the stomach flow to the esophagus and pharynx, may be UES or LES problem or both • Hiatal Hernia: LES may malfunction allowing reflux into esophagus • Congenital Malformation: stenosis, see figure 9-4

10. Neurophysiological Terms • Taste Buds (cells): chemoreceptors for gustation • Chemoreceptors: Neural receptors that respond to specific chemical composition • Papillae: Prominences • Taste Pore: opening in lingual epithelium that houses taste cell • Microvilli: small, hairlike fibers projecting from the taste cell into the taste pore • Mechanoreceptors: neural receptors designed to sense mechanical forces • Glabrous: Hairless • Meissner’s Corpuscles: Superficial cutaneous mechanoreceptors for minute movement • Merkel disk receptors: Superficial cutaneous mechanoreceptors for light pressure • Pacinian Corpuscles: deep cutaneous mechanoreceptors for deep pressure • Ruffini endings: deep cutaneous mechanoreceptors for tissue stretch • Nociceptors: Pain sensors • Salivation: Production and release of saliva into to oral cavity • Mucus: Thick, high-viscosity saliva • Serous:Thin, low viscosity saliva

11. Neurophysiology • Gustation • Taste receptors (taste buds, taste cells) • Class of sensors known as chemoreceptors • Found within the epithelia of the with in papillae or prominences • Taste pour: opening in lingual epithelium that houses taste cell, permits isolation of the tasted substance • Microvilli: small hairlike fibers projecting from the taste cell into the taste pore, holds sample of food in taste pore

12. Neurophysiology • Gustation • Taste mediated by 3 cranial nerves • V!! mediates sense of taste from anterior 2/3 of the tongue, sweet and sour sensations, and of palate. Sides transmit salt and sour. • IX mediates sense of taste, primarily of bitterness from posterior 1/3 of tongue. Sides transmit salt and sour • X mediates sense of taste from epiglottis and esophagus • Umami: taste receptor which processes monosodium glutamate.

13. Neurophysiology • Gustation • Taste VII CN • Taste receptor • Geniculate ganglion • Medullary solitary tract (NST) • Rostral and lateral aspects of ST nucleus for gustation • Ventral posterior medial nucleus of thalamus • Information relayed ipsilaterally to the sensory cortex (post central gyrus),anterior portion of the insula of the cerebral cortex, and to the operculum overlying the insula.

14. Neurophysiology • Gustation • Taste IX CN • Taste receptor • Petrosal ganglion • Medullary solitary tract (ST) • Rostral and lateral aspects of ST nucleus for gustation • Ventral posterior medial nucleus of thalamus • Information relayed ipsilaterally to the sensory cortex (post central gyrus),anterior portion of the insula of the cerebral cortex, and to the operculum overlying the insula.

15. Neurophysiology • Gustation • Taste X CN (epiglottal and esophageal) • Taste receptor • Nodose ganglion • Rostral and lateral aspects of ST nucleus for gustation • Ventral posterior medial nucleus of thalamus • Information relayed ipsilaterally to the sensory cortex (post central gyrus),anterior portion of the insula of the cerebral cortex, and to the operculum overlying the insula. • Taste and small probably integrated in the insula • Fibers from the insula project to the limbic and motor regions of the brainstem

16. Neurophysiology • Gustation • NTS projects to the motor cortex, specifically area serving the tongue • Tastes (sweet {carbohydrates}, protein {umami} salt) will elicit salivation, ingestive responses • Tongue protrusion to receive the food • Release of insulin • Mastication and deglutition

17. Neurophysiology • Gustation • NTS projects to the motor cortex, specifically area serving the tongue • Tastes, bitter and sour mat typify poison and elicit a protective response • Gagging • Coughing • Apnea • Salivation (encapsulates the material and protects the oral cavity

18. Neurophysiology • Gustation • NTS projects to the motor cortex, specifically area serving the tongue • Taste can elicit motor responses that may or may not be under volitional control • Gag response • Elevation of the larynx • Clamping of the vocal folds • Elevation of the velum • Protrusion of the tongue

19. Neurophysiology • Gustation • NTS projects to the motor cortex, specifically area serving the tongue • Taste can elicit motor responses that may or may not be under volitional control • Coughing • Tightly closing VF and supraglottic structures • Compressing of abdomen and thorax • Forcefully blowing VF apart

20. Neurophysiology • Gustation • Deglutition is made up of a complex set of motor responses dictated by stimuli present in the oral and pharyngeal spaces Explain this

21. Neurophysiology • Olfaction • Olfactory chemoreceptors in nasal mucus membrane • Sense of smell transmitted to olfactory bulb in cranial space • Then transmitted over olfactory tract to olfactory region of the cortex, and from some to the thalamus • Amygdala to hypothalamus • Anterior olfactory nucleus • Piriform cortex • Olfactory tubercle • Entorhinal cortex to hippocampus in the temporal lobe

22. Neurophysiology • Olfaction • Arrives at cerebral cortex through multiple pathways and serves as a stimulus to • Emotion and motivation (amygdala) • Physiological responses (hypothalamus) • Memory encoding (hippocampus) • Olfactory discrimination (orbitofrontal region of the cerebral cortex)

23. Neurophysiology • Tactile Sense • In face and oral cavity, primarily mediated by V, but IX and X are associated • Mechanoreceptors are sensative to physical contact, receptors vary according to type of touch • Deep pressure has the potential to stimulate a larger field and greater array of sensors than light pressure, an issue that is important in treatment of dysphagia • Vibration sense is a subclass of tactile sense • Best Frequency: The frequency if vibration at which a sensor responds most effectively

24. Neurophysiology • Thermal Receptors • In face and oral cavity, primarily mediated by V, but IX and X are associated • Same as pain sensors, bare nerve endings • Differentiate warm, hot, cool, cold: receptors are tuned to particular temperatures • Have a tonic, ongoing charge • With high temperatures, heat sensors stop firing and pain sensors fire • Perception of pain can interfere with the ability to swallow and swallowing responses

25. Neurophysiology • Muscle stretch and Tension sense • In face and oral cavity, primarily mediated by V, but IX and X are associated • Stretch receptors are found in oral muscles • Masseter • Temporalis • Lateral and medial Pterygoid • Genioglossus • palatoglossus • Muscle Spindle fibers (MSF) • Return a muscle to its original position following passive stretching (pulling down on relaxed jaw) • MSF designed to maintain a muscle at a preset length • MSF generally inhibited during active contraction

26. Neurophysiology • Muscle stretch and Tension sense • Muscle Tension • Sensed by Golgi tendon organs (GTOs) within tendons and facia • Muscle tone • Perception of resistance to passive movement of a stretching • regulated partially through interaction of muscle spindles and GTOs • High tone of spasticity due to inadequately inhibited response from a muscle spindle sensor • Low tone results from inadequate tonic stimulation either LMN disease or cerebellar lesion • Muscular rigidity results from a basal ganglia lesion and demonstrates a cocontraction of agonist and antagonist

27. Neurophysiology Salivation Response • Not a sensory system but rather a motor response • Product of 3 glands: parotid, sublingual, submandibular • Stimulation of taste receptors on anterior 2/3 of tongue mediated by VII via NS of dorsal pons (sublingual and submandibular glands) • Stimulation of taste receptors on posterior 1/3 of tongue mediated by IX via inferior and superior salivatory nuclei of the pons (parotid gland)

28. Neurophysiology Salivation Response • Parotid produces • Sublingual: produces mucus, a high-viscosity protein rich secretion that helps in formation of the bolus for food • Submandibular: produces serous (low viscosity, thinner consistency) and mucus secretions, lubricates the bolus • Parotid: produces serous saliva which helps the bolus to be transported through the pharynx • Salivary response stimulated by sight, smell, and taste of food