physiology of swallowing PRESENTATION BY ENT TEAM

PRESENTATION BY ENT TEAM

1. Physiology of swallowing By: Nur Izzaty Nadia

2. OUTLINE Stages of swallowing Oral: preparatory Oral: propulsive Pharyngeal Oesophageal Neurologic control of swallowing Cranial nerves Brainstem controls Central neurologic control Factors influence the swallowing Age Tracheostomy Laryngectomy Surgery of mouth and tongue

3. Swallowing A process whereby food or fluid is transported from the mouth into the stomach Requires coordinated activity of muscles in oral cavity, pharynx, larynx, and oesophagus voluntarily and involuntarily Typically divided into three distinct phases Oral Pharyngeal Oesophageal

4. 1. Oral phase (Preparatory) Under voluntary control Occurs with the presence of food/drink in the mouth Chewing, grinding motion mixes the food to aid in tasting and digestion The jaw elevators and depressors play a key role in bolus preparation before the swallowing is initiated by grinding and reducing the food between the teeth

5. For solid food, dentition is important for chewing and crushing of food by Incisor for cutting Canine for tearing Molars for grinding Buccinator is used to return food from vestibule to oral cavity

6. Innervation of major muscle related to swallowing

7. As the bolus is formed: The base of tongue approximates with the soft palate to hold the bolus within the oral cavity Soft palate is lowered under the action of palatoglossal and palatopharyngeus which approximated the respective arches to the post part of tongue. (the airway remain open) Mediated by: Palatoglossus:CN IX Stylohyoid: CN VII Styloglossus : CN XII Post belly of digastric: CN VII

8. The lingual surface of the tongue grooves at the midline to collect the bolus Action by the intrinsic muscles of the tongue (CNXII) Primarily by the vertical muscles Secondary by the transverse muscles

9. To further aid in mastication and bolus preparation Sensory inputs from Hard palate Cheek Taste from Ant 2/3 rd of tongue Soft palate Sensory inputs are transmitted via CN VII, CN V

10. II. Oral phase (Propulsive)

11. II. PHARYNGEAL STAGE - initiated when the bolus hits the post pharyngeal wall

12. II. PHARYNGEAL STAGE

13. II. PHARYNGEAL STAGE Bolus is directed laterally through the piriform fossa , aided by successive contractions of the pharyngeal constrictors Cricopharyngeus relaxes,allowing bolus to pass into oesophagus initiating the oesophageal phase

14. II. Pharyngeal stage-what aids in the propulsion of the food bolus in the pharyngeal stage? UES relaxes, Laryngeal inlet and nasopharynx closes

15. Piston pump action and hypopharyngeal suction pump action Piston pump action Tongue compression against post pharyngeal wall, results in POSITIVE PRESSURE applied to bolus Thus, the bolus is propelled out Hypopharyngeal suction pump action Elevation of larynx, results in a traction force that opens up the UES resulting in a NEGATIVE PRESSURE that sucks the bolus in gravity assisted

16. II. Pharyngeal stage-how does the epiglottis close of the laryngeal inlet?

17. (1) Contraction of the suprahyoid muscles will elevate the hyoid anteriorly and superiorly Elevation of the larynx is achieved via action of suprahyoid muscles resulting in pulling the larynx anteroposteriorly away from the cervical spine resulting in negative pressure at entrance of oesophagus

18. (2) Architecture of the epiglottis: Convex at the tubercle(refer black arrow pointing in) Elastin fibers return it to the resting position Horizontally directed collagen fibres at its folding plane facilitates deflection (refer grey arrow)

19. (3)Laryngeal closure is achieved via: approximation of aryepiglottic folds, false cords and true cords (glottic closure reflex) Epiglottic deflection Compression of the quadrangular membrane

20. II. Pharyngeal stage

21. RELAXATION OF THE SPHINCTER Nucleus Ambiguus sends impulse to CN X to inhibit tonic contraction Relaxation of the cricopharyngeus Anterior movement of the hyoid, ie elevation of the larynx Distension of the UES sphincter via pressure applied by the bolus Passive collapse of the UES after the bolus has passed thru the sphincter Closure of the UES by active contraction of the cricopharyngeus

22. III. Oesophageal stage Primary, secondary, tertiary waveforms

23. Primary peristaltic wave- passes bolus down the esophagus at a rate of 4cm/ sec secondary peristaltic wave- arise locally in response to esophageal distension Tertiary peristaltic wave- irregular and non propulsive, involving long segment of esophagus, usually during stress

24. III. Oesophageal stage

25. Summary

26. The swallow reflex is a complex neurologic event involving participation of high cortical centers The initiation of swallowing can either be as a voluntary act or a reflex as the result of stimulation of the appropriate mucosa in the oral cavity The voluntary initiation of swallowing involves bilateral areas of the prefrontal, frontal and parietal cortices These include both the primary sensory and motor cortex, as well as the prefrontal swallowing areas which are located just anterior to precentral gyrus in the primary motor cortex, corresponding to Brodman’s area 6 Neural control of swallowing

27. There are important areas within the brainstem necessary for the control of swallowing and these are located particularly within the medulla Descending pathways project to these medullary swallowing centres from the frontal swallowing areas within the cortex These probably include pathways in both dorsolateral and ventromedial descending systems through the ventral and lateral corticobulbar tracts

28. Sensory input from oral cavity, epiglottis, oral mucosa sent to nucleus solitarius and spinal trigeminal nucleus through cranial nerves IX, X Efferent pathways: Nucleus ambiguus for muscles of palate, pharynx and larynx Hypoglossal nucleus for muscles of tongue Motor nuclei of trigeminal nerve for muscles of jaw Motor nuclei of facial nerve for lips Neurologic deficits in any of these areas can result in dysphagia

29. FACTORS INFLUENCE SWALLOWING Age Infancy: larynx is higher level,high epiglottis Diet is more liquid Obligate nasal breathers during feeding Oropharyngeal sphincter prevents milk trickling into the pharynx(during sucking) Elderly Resting pressure of the UES is lower Wet swallows significantly shortened the interval btwn laryngeal closure and UES relaxation compared to dry swallows

30. EFFECT OF CLEFT PALATE ON SWALLOWING levator veli palatini , palatopharyngeus , superior pharyngeal constrictor function is impaired. In cleft palate, the muscles are attached to the bony cleft edges. The palatopharyngeus muscle is hypertrophied in cleft palate Resulting in nasal regurgitation, inadequate closure of the nasopharyngeal isthmus, inability to achieve a tight seal during sucking.

31. EFFECT OF SURGERY ON SWALLOWING Tracheostomy Movement of the larynx and upper trachea to the skin and ant soft tissue is impaired Restriction of laryngeal elevation Inflated tracheostomy cuff causes accumulation of saliva above the cuff Post tracheostomy - scarring can impair laryngeal elevation

32. EFFECTS OF LARYNGECTOMY ON SWALLOWING Stenosis Significant impairment of the pharyngeal phase of swallowing In the absence of larynx, unable to generate hypopharyngeal suction pump action Absence of laryngeal descent prevents propulsion of the tail of the bolus into the upper oesophagus If pharynx is closed vertically- results in the presence of pseudo vallecula (U shaped fold of pharynx behind the base of tongue) Food can get entrapped causing dysphagia

33. SURGERY OF THE MOUTH AND TONGUE Desensitization , fixation or resection of the ant 2/3 of tongue impairs the oral phase of swallowing Jaw resection impairs mastication Base of tongue surgery disturbs the oropharyngeal sphincter Total resection of the pharynx disrupts the pharyngeal stage of swallowing

34. References Scott Brown Otorhinolaringology and Head and Neck Surgery – 7th Edition Cummings ORL-HNS 6th Edition Costanzo, Linda S.  Physiology . 6th ed. Elsevier, 2018.  Matsuo, K. and J. Palmer. “Anatomy and physiology of feeding and swallowing: normal and abnormal.”  Physical medicine and rehabilitation clinics of North America  19 4 (2008): 691-707, vii .