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Physiology of swallowing
This document discusses the physiology of swallowing. It involves three phases - oral, pharyngeal, and esophageal. The oral phase involves preparing and moving food to the back of the throat using tongue and jaw muscles. The pharyngeal phase is involuntary and uses throat muscles to push food to the esophagus. The esophageal phase uses peristaltic waves to move food to the stomach through the esophagus. Swallowing is coordinated by brainstem centers and involves various cranial nerves and muscles.
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Physiology of swallowing
- 1. PHYSIOLOGY OF SWALLOWING Dr Nadhirah Supervisor: Prof Madya Dr Marina PHYSIOLOGY OF SWALLOWING Dr Jamal Nasser bin Salleh Supervisor : Prof Madya Dr Marina bt Baki
- 2. INTRODUCTION • Deglutition involvesco-ordinated activity of muscles of oral cavity, pharynx, larynx and esophagus • Definition : Passage of a food bolus or liquid from oral cavity to the stomach via the pharynx and esophagus • Phases : • Oral – voluntary • Pharyngeal involuntary/autonomic • Esophageal
- 3. ANATOMY Components of deglutition : 1)Passage of bolus from oral cavity to stomach 2) Protection of airway 3) Inhibition of air entry into stomach
- 4. Oral phase 1) Oralpreparatory phase 2) Oral phase proper • Voluntary • Food prepared for swallowing • Tongue plays vital role
- 5. Oral Preparatory Phase •Breaking down of food in the oral cavity • Food chewed & mixed with saliva Bolus • The elevators of lower jaw play an important role in bolus preparation • Tongue (vital role) : intrinsic muscles alter the shape, extrinsic muscles change its position within the oral cavity – helping in chewing the food by dental occlusion • Occlusal action of the lips help in creating an effective seal preventing bolus from dribbling out of oral cavity • Action of buccinators muscle helps in pushing the bolus out of the vestibule into the oral cavity proper
- 6. Bolus Formation • Themost important function of preparatory phase • Involves repeated transfer of food from oral cavity to oropharynx surface of tongue • Bolus accumulates on the oropharyngeal surface of tongue due to repeated cycles of upward and downward movement of the tongue
- 7. Oral Phase Proper •The bolus is moved towards the back of the tongue • Contraction of soft palate prevents nasal regurgitation • Soft palate also prevents premature movement of bolus into oropharynx • Once the bolus is of suitable consistency the transit from mouth to oropharynx just take a couple of seconds • Tongue plays a vital role during this phase. Its instrinsic muscles contract and reduce size, while genioglossus muscle elevates the tongue towards the plate. • The elevation of the mandible cause suprahyoid muscles raised the hyoid bone.
- 8. Anatomy of Pharynx •Midline tube about 15cm long • Continous with nasal cavities and larynx above and esophagus below • The anterior wall of pharynx is incomplete and is composed of posterior part of tongue posteriorly and larynx inferiorly • Divided into nasopharynx, oropharynx, laryngopharyx according to those structures lying anteriorly • The reminder of pharynx resembles the gut. It has 4 layers ie areolar, muscular, sub mucous and inner mucous membrane (ouside inwards)
- 9. Anatomy of Pharynx(cont) • The muscular layer has 2 component ie longitudinal and circular muscle layers • Circular muscles : superior, middle, inferior constrictor muscles • Inferior constrictor muscle has 2 components : thyropharyngeus and cricopharyngeus • Except the cricopharyngeus muscles all the other muscles acting on the pharynx are paired • The cricopharynx forms a distinct sphinter at the point where laryngopharynx enters the esophagus
- 10. Pharyngeal Phase (pumping actionof tongue and hypopharyngeal suction) • This phase is reflexive in nature • It takes a second for the bolus to transverse the pharynx and reach the cricopharyngeal area • Contraction of diaphragm is inhibited making simultaneous breathing and swallowing impossible • Soft palate is elevated in order to seal off the nasopharynx (by Tensor palatine and Levator palatine muscles) • Vocal cords adduct protecting the airway • As the bolus passes the palatoglossal and palatopharyngeal folds the act of swallowing become reflexive
- 12. Functions of triggerpoints in oropharynx • Stimulation of trigger points present in the oropharynx starts off the pharyngeal reflexive stage of swallowing • Trigger points are at the the faucial arches and mucosa of the posterior pharyngeal wall • These trigger points are innervated by CN IX • Stimulation of these trigger points causes dilatation of pharynx due to relaxation of the constrictors, and elevation of pharynx & larynx due to contraction of longitudinal muscles • The pharynx constrict behind the bolus thereby propelling it • Contraction of the inferior constrictor muscle moves the bolus towards esophagus
- 14. Importance of laryngealelevation during pharyngeal stage • Narrows the laryngeal inlet • Ensures better sealing of the laryngeal inlet by the downturned epiglottis • Laryngeal elevation also contributes to dilatation of pharynx • The laryngeal inlet is closed due to the actions of interarythenoid, aryepiglottic and thryoepiglottic muscles.
- 15. Role of epiglottisin the pharyngeal phase • The movement of epiglottis occurs in 2 stages • The epiglottis moves from vertical – horizontal position • The upper third of epiglottis moves below the horizontal to a slightly lower level to cover the narrowed laryngeal inlet • The bolus during the course of the swallow impinges on the epiglottis and gets diverted to the lateral food channels • Solid food tends to go behind the epiglottis into the postcricoid area • Liquid food gets split by the epiglottis and passes via the pyriform fossa
- 16.
- 17. Esophageal phase • Purelyreflexive • Begins by relaxing the cricopharyngeal sphinter • Time taken : 10 – 15 secs • Primary/secondary/tertiary peristaltic waves play active roles in this phase • peristaltic movements of esophagus takes the bolus down to the stomach
- 18. Regurgitation of foodback into esophagus is prevented by : • Tone of gastro-esophageal sphinter • Negative intra thoracic pressure • Pinch-cock effect of diaphragm • Mucosal folds • Esophagogastric angle • Slight positive intra abdominal pressure
- 19. Neurological Representation ofSwallowing • Complex sensorimotor activity • Involving organized interactions between cortical, cerebellar, bulbar and peripheral systems • Cranial nerves involve : - V trigeminal - VII facial - IX Glossopharyngeal - X Vagus - XI spinal accessory - XII Hypoglossal
- 20. Innervation of majormuscles related to swallowing Cranial nerves Muscles Trigeminal Nerve (V) Masticatory muscles Mylohyoid Tensor veli palatini Anterior belly of digastrics Facial nerve (VII) Facial muscle Stylohyoid Posterior belly of digastrics
- 21. V - TrigeminalNerve Trigeminal Ganglion Mandibular Branch Buccal Nerve Ophthalmic Branch Maxillary Branch Inferior Alveolar Nerve Lingual Nervenn
- 22.
- 23. VII - FacialNerve Motor Branches General Motor – branches • Buccal – orbicularis oris, buccinator (masticator), risorius (lip retractor) • Mandibular – orbicularis oris, mentalis (lip protruder) • Cervical – platysma (mandibular depressor) Visceral Motor • Salivary glands (hitchhike with CN V) • Palatal & nasal mucosal membranes
- 24. VII – FacialNerve Sensory Branches Chorda Tympani
- 25. Facial Muscles- Importantfor Swallow Orbicularis Oris Buccinator Mentalis
- 26.
- 27. Cranial nerves Muscles GlossopharyngealNerve (IX) Stylopharyngeus Vagus nerve (X) Levator veli palatine Palatopharyngeous Salpingopharyngeous Intrinsic laryngeal muscles Cricopharyngeus Pharyngeal constrictors Innervation of major muscles related to swallowing
- 28. Cranial nerves Muscles Hypoglossalnerve (XII) Intrinsic tongue muscles Hyoglossus Geniohyoid Genioglossus Styloglossus Thyrohyoid Innervation of major muscles related to swallowing
- 29. Sensory afferents I. Trigeminal •Teeth and gums, palate and roof of the pharynx II. Glossopharyngeal • Posterior third of the tongue, pharynx, area of the tonsil III. Vagus • Pharynx, larynx
- 30. Trigeminal Nerve (V) •Sensory nerve of the face and neck • Branches • Maxillary (sensory) : upper lip, maxillary teeth and palate, small area of pharynx • Mandibular (sensory + motor) - Sensory : anterior 2/3 tongue (not taste) , TMJ, mucous membrane of mouth & buccal, gums and mandibular teeth - Motor : mastication muscles (temporalis, masseter, pterygoids), tensor muscles (tensor veli palatini), suprahyoid muscles ( myolohyoid & anterior belly digastric muscle)
- 31. VII – FacialNerve • Sensory + Motor Components • Innervates superficial face and neck muscles • Contains special sensory and visceral motor components • Special Sensory- Chorda Tympani: taste for anterior 2/3 of tongue & other sensory for hard/soft palate
- 32. Brainstem centers • Centralpattern generators – Dorsomedial & Ventrolateral • Mainly involves nucleus of the tractus solitarius and the nucleus ambiguous • Programs directing the sequential movements of the various muscles involved
- 33. Brainstem centers • Activatedby • Descending pathways from the motor cortex (cortico bulbar tracts) • Ascending pathways from sensory structures within the oropharynx and esophagus Nucleus of the tractus solitarius receives the descending and peripheral afferent influences
- 34. Dorsomedial pattern generator •Resides in the medial reticular formation of the rostral medulla and the reticulum adjacent to the nucleus tractus solitarius • Initiation and organization of the swallowing sequence
- 35. Ventrolateral pattern generator •Lies near the nucleus ambiguous and its surrounding reticular formation • Serves primarily as a connecting pathway to motor nuclei such as the nucleus ambiguus and the dorsal motor nucleus of the vagus, which directly control motor output to the pharyngeal musculature and proximal esophagus
- 36. Cortical control tobrainstem structures Inferior precentral gyrus • Cortical representations of tongue and face • Bilaterally symmetrical activation
- 37. Other cortical areasinvolved in swallowing Supplementary motor area • Preparation for volitional swallowing Anterior cingulate cortex • Monitoring autonomic and vegetative functions.
- 38. Other cortical areasinvolved in swallowing Anterior insula, particularly on the right • Activation during volitional swallowing • Allows gustatory and other intraoral sensations to modulate swallowing. • Lesions increase the swallowing threshold and delay the pharyngeal phase of swallowing
- 39. Other higher centersin swallowing Cerebellum • Esp left-sided activation • Coordination, timing, and sequencing of swallowing • controls output for the motor nuclei of cranial nerves V, VII, and XII Putamen • Activated during volitional swallowing
- 40.
Editor's Notes
- #3 Normal deglutition is a smooth coordinated process that involves a complex of series of voluntary and involuntary neuromuscular contractions which can divided into 3 phases.
- #5 The oral phase may be split into the preparatory phase where the food is taken into the mouth and broken down, and oral phase proper where the bolus is moved to the back of the tongue.
- #12 The tongue elevated, blocking the oral cavity Soft palate blocks nasopharynx Vc close glottis and larynx moves up Epiglottis covers larynx
- #18 After the food enters the esophagus, the cricopharyngeal sphinter will close,and peristaltic movements of esophagus takes the bolus down to the stomach. Gastroesophageal sphinter at lower end esophagus relaxes well before peristaltic wave reaches and permit fluid to pass. Bolus of food is passed by contraction of peristaltic waves and then the spinter closes.