Structures involved in phases of swallowing PNS and CNS.pptx

anatomy

1. Structures involved in phases of swallowing PNS and CNS control of mastication and swallowing Made by:- Vivek Kumar Guided by:- Appas Saha

2. Introduction Swallowing is the continuous process of deglutition from placement of the food in the mouth, its manipulation in the oral cavity, and its passage through the oral cavity, pharynx, and oesophagus until it enters into the stomach. Deglutition, more commonly referred to as swallowing, is defined as the semiautomatic motor action of the muscles of the respiratory and gastrointestinal tracts that propels food from the oral cavity into the stomach (Miller, 1986). The act of swallowing is complex because respiration, swallowing, and phonation all occur at one anatomic location—the region of the pharynx and larynx. To be successful, normal swallowing requires the coordination of 31 muscles, 6 cranial nerves, and multiple levels of the central nervous system, including the brain stem and cerebral cortex ( Bosma , 1986).

3. The complex function of swallowing involves anatomical structures extending from the oral cavity (lips, teeth, tongue, cheeks, oral vestibular, palate and palatal arches) to the pharynx, larynx, hypopharynx and the esophagus . Swallowing is a subset of the continuous series of automatic event that transport food from the level of thr incisor teeth to the stomach and, in normal feeding, swallowing does not exist separately from that continuous series.

4. The conventional division of the human swallow into separate stages is usually ascribed in Magendie who introduced his description of the swallow with the following: “To facilitate a study we divide deglutition into three periods. In the first, the food passes from the mouth to the pharynx; in the second it passes the opening of the glottis, that of the nasal canals, and arrives at the oesophagus ; in the third, it passes through this tube and enters the stomach. The conventional first stage is usually described as voluntary and as moving food up to the fauces : the conventional second stage is usually described as a reflex which moves food through the fauces and then through the pharynx.

5. Structures involved in Swallowing Oral Cavity Roof: The hard and soft palates separate the oral cavity from the nasal cavities. Floor: The floor is formed by the tongue and a muscular diaphragm formed by the muscles in the floor of the oral cavity. Lateral walls: The lateral walls are formed by the cheeks. Posteriorly: It opens into the pharynx at the oropharyngeal isthmus, which is bound superiorly by the soft palate, inferiorly by the tongue, and laterally on either sides by the faucial pillars formed by the palatoglossal (anterior arch) and palatopharyngeal (posterior arch) muscles. Anteriorly: It communicates with the oral vestibule.

6. Teeth -Teeth are responsible for chewing, for biting, and for grinding. Teeth are responsible for pulverizing the food and bolus formation Lips - The lips act as valves of oral cavity. The orbicularis oris acts as the sphincter that controls the entry and exit of the bolus from the mouth and upper alimentary and respiratory tracts. Cheeks - Buccal mucosa and the deeper buccinators muscle provide enough force and modification to the tongue to prepare a bolus and push it medially to the teeth and tongue. Tongue - It is a mobile structure made of muscles, situated in the floor of the mouth, that sits in the oral cavity and in the oropharynx . It is an important organ for deglutition, taste, and speech. It has oral and pharyngeal parts and is attached to the hyoid bone, mandible, styloid processes, soft palate, and pharyngeal wall by its muscles.

7. Hard Palate-The hard palate forms the partition between the oral and nasal cavities and is composed of the palatine processes of each maxilla anteriorly and the horizontal plates of each palatine bone posteriorly. Its posterior margin gives attachment to the soft palate. The alveolar arch lies anterior and lateral to the oral surface of the hard palate. Soft Palate-The soft palate separates the nasopharynx from the oropharynx. It is lined by mucous membrane and consists of palatine aponeurosis (flattened tensor veli palatini tendon), taste buds, mucous glands, and muscles. The palatine aponeurosis splits in the midline to enclose the musculus uvulae, which forms the posterior free hanging midline projection, the uvula. The soft palate on elevation comes into contact with Passavant’s ridge, closing the pharyngeal isthmus during swallowing. This separates the nasopharynx from the oropharynx, thus preventing nasal regurgitation. Depression of the soft palate closes the oropharyngeal isthmus.

8. Larynx The larynx is composed of a cartilaginous framework held together by muscles and ligaments. The laryngeal cavity lies in continuity with the pharynx superiorly and the trachea inferiorly. The intrinsic laryngeal muscles are responsible for tensing and relaxing the vocal ligaments, opening and closing the rima glottidis, adjusting the laryngeal vestibule dimensions, and facilitating closure of the rima vestibuli and laryngeal inlet. Unpaired cartilages: thyroid, cricoid, and epiglottis Paired cartilages: arytenoid, corniculate, and cuneiform

9. The laryngeal adductor reflex (LAR), also called the glottic closure reflex, is a brainstem-mediated, involuntary reflex arc, which prevents substances from inappropriately entering the airway. The LAR is a bilateral thyroarytenoid (TA) muscle response to mechanical or chemical irritation of the laryngeal mucosa. During speech and swallowing, mechanoreceptors in the laryngeal mucosa are subjected to pressures generated by vocal fold closure, which are similar to these air puff stimuli. During swallowing, the action of the intrinsic and extrinsic muscles results in the closure of the rima glottides and the rima vestibule. Narrowing of the laryngeal inlet occurs along with upward and forward movement of the larynx.

10. As a result the epiglottis moves toward the arytenoid cartilages with narrowing down or closure of the laryngeal inlet. Elevation of the larynx by the suprahyoid muscles also opens the pharyngoesophageal segment. This sequence of events directs the solids and liquids through the piriform fossae into the esophagus and prevents them from entering the airway shows the relations of the oral cavity, larynx, pharynx, and esophagus.

11. Oropharynx The oropharynx is the region of the pharynx posterior to the oral cavity. It extends from the inferior level of the soft palate to the upper margin of the epiglottis. Its posterior wall is anterior to the second and third cervical vertebrae. It includes the posterior one-third of the tongue (tongue base with collection of lymphoid tissue, the lingual tonsils), palatine tonsils, soft palate, oropharyngeal mucosa, and constrictor muscles.

12. Hypopharynx The hypopharynx, or laryngopharynx, extends from the level of the hyoid bone (and valleculae ) to the cricopharyngeus . It is continuous superiorly with the oropharynx and inferiorly with the cervical esophagus (level of C6). The posterior oropharyngeal wall continues inferiorly as the posterior wall of the hypopharynx, behind which lies the retropharyngeal space. The pharyngeal wall consists of four layers from inside out: mucous membrane, pharyngobasilar fascia, muscular layer, and buccopharyngeal fascia. The muscular layer consists of an outer circular and an inner longitudinal muscle layer.

13. Contraction of the muscles leads to constriction of the pharynx. Sequential contraction of the constrictor muscles from above downward results in the propulsion of the food bolus from the pharynx to the esophagus. The longitudinal muscles elevate the pharyngeal wall or pull the pharyngeal wall up and over a bolus of food passing through the pharynx into the esophagus

14. Esophagus The esophagus is a muscular tube, about 23–25 cm, extending from the pharynx to the stomach. It begins at the inferior border of the cricoid cartilage, opposite C6 vertebra, and ends at the cardiac opening of the stomach, opposite T11 vertebra. It has three constrictions, the first at the cricopharyngeal sphincter (15 cm from the incisors), the second where it is crossed by the aortic arch and the left main bronchus (23 cm from the incisors), and the third where it pierces the diaphragm (40 cm from the incisors). The esophageal wall is made up of four layers. From outside in, these are as follows: Outer fibrous layer Muscular layer (outer longitudinal layer and inner circular layer which is continuous with the inferior constrictor muscle of the pharynx) Submucous or areolar layer (consists of blood vessels, nerves, mucous glands) Internal mucosal layer (covered throughout with a thick layer of stratified squamous epithelium with minute papillae on the surface)

15. Difference between adult and infant The anatomy of the swallowing passage differs in infants and adults. In infants, the teeth are not yet erupted, the hard palate is fl atter, and the hyoid bone and the larynx are at a higher position in the neck (C2–C3 level). The epiglottis as a result touches the posterior end of the soft palate. The larynx is thus in direct communication with the nasopharynx, but the oropharynx is closed away from the airway during swallowing. This prevents food from entering the airway and protects the infant from aspiration. During the second year of life, the neck elongates and the larynx starts descending to a lower position. In adults, as a result, the epiglottis is no longer in contact with the soft palate, and the pharynx elongates vertically and becomes a part of the airway. These developmental changes increase the risk of aspiration in adults.

16. Phases of Swallowing

17. Oral Phase The oral phase of swallowing is composed of a sequence of events involving incising of food by the front teeth, transport of food towards the posterior teeth, mastication and chewing of the food into smaller pieces, and directing the food bolus towards the pharynx. The oral phase of swallowing is composed of a sequence of events involving incising of food by the front teeth, transport of food towards the posterior teeth, mastication and chewing of the food into smaller pieces, and directing the food bolus towards the pharynx. Oral Preparatory Phase After liquid is taken into the mouth, the bolus is held between the anterior part of the floor of the mouth or tongue surface and the hard palate surrounded by the upper dental arch. The orbicularis oris contracts to seal the lips tightly. Jaw closure is brought about by the contraction of the masticatory muscles. Contraction of the buccinator keeps the cheek pressed against the teeth, keeping the cheek taut and preventing food from accumulating between the teeth and the cheek. The soft palate comes in contact with the posterior end of the tongue due to contraction of the palatoglossal and palatopharyngeal arches, sealing the oral cavity from the oropharynx, thus preventing entry of food into the oropharynx.

18. Tongue movements push the food onto the grinding surfaces of the teeth. The food is chewed and mixed with the salivary secretions to change its consistency to prepare it for the swallow. During this phase, breathing through the nose continues as the airway is open and the larynx and pharynx are at rest. Any weakness of the tongue or soft palate muscles can lead to leakage of food into the oropharynx during this phase.

19. Oral Propulsive Phase During this stage, the tongue tip is raised by the action of the intrinsic muscles of the tongue and the genioglossus so that the tongue touches the alveolar ridge of the hard palate just posterior to the upper teeth. The posterior end of the tongue is depressed to open the posterior portion of the oral cavity. Elevation of the mandible helps in elevating the hyoid bone (brought about by the suprahyoid muscles) and the floor of the mouth. Simultaneously, the tongue surface also moves in the upward direction, so that the area of tongue–palate contact gradually increases from anterior to posterior and the liquid bolus is squeezed along the palate into the oropharynx. When the bolus reaches the posterior part of the tongue, the soft palate is elevated by the levator and tensor palatini muscles, sealing the nasopharynx from the oropharynx, thus preventing nasal regurgitation. Weakness of the palatal muscles or structural abnormalities like a cleft palate can lead to regurgitation of food into the nasopharynx and nasal cavity. When drinking liquids, the pharyngeal phase normally begins during oral propulsion.

20. Process Model of Feeding Once ingested, the food is carried by tongue movements to the postcanine region. The tongue then rotates laterally. This places the food onto the occlusal surface of lower teeth for the next stage of food processing Stage I Transport Food Processing This is the next immediate stage after stage 1 transport. The food is broken down into smaller particles by chewing and softened by salivary secretions to achieve a proper consistency to make it ready for bolus formation and swallow. Chewing continues until all of the food is prepared. As opposed to the oral preparatory phase during drinking of liquids, there is no sealing of the posterior oral cavity from the pharynx by contact of the posterior tongue with the soft palate during food processing.

21. Stage II Transport Stage II transport is similar to the oral propulsive stage with a liquid bolus. The anterior end of the tongue comes into contact with the hard palate just behind the upper incisors. The area of tongue–palate contact gradually expands anteroposteriorly , squeezing the processed food posteriorly along the palate to the oropharynx. Stage II transport primarily occurs secondary to tongue movements and does not require gravity. The transported food accumulates on the pharyngeal surface of the tongue and in the valleculae , while the food remaining in the oral cavity is chewed and the size of the bolus in the oropharynx progressively enlarges. In normal individuals, the duration of bolus aggregation in the oropharynx while eating solid food varies from a fraction of a second to about 10 s.

22. Pharyngeal Phase This phase is composed of a series of sequential events for the passage of the food bolus from the pharynx to the esophagus along with protection of the airway and nasopharynx. The passage of food bolus through the fauces was earlier thought to act as a sensory input to trigger the initiation of the pharyngeal stage. The sensory input for the initiation of this reflex is carried by the vagus and the glossopharyngeal nerves to the swallowing center in the brainstem. Also while eating solid food, the chewed bolus is aggregated in the oropharynx or valleculae before swallowing. When the bolus enters the oropharynx, the nasopharynx is closed by elevation and contact of the soft palate with the lateral and posterior pharyngeal walls, thus preventing nasal regurgitation. This velopharyngeal closure, brought about by the levator palatine muscles also provides a surface to propel the bolus in a downward direction. The velopharyngeal closure is shortly followed by reflex closure of the laryngeal inlet. Closure of the true and false vocal cords occurs. The hyoid bone and larynx are pulled upward and forward due to suprahyoid and thyrohyoid muscle contraction, so that the larynx is covered by the tongue base.

23. Backward movement of the epiglottis, probably thought to be due to hyolaryngeal elevation, pharyngeal constriction, bolus movement, and tongue base retraction covers the laryngeal inlet . This results in apnea which may last from 0.5 to 1.5 s. Retraction of the base tongue pushes the bolus against the pharyngeal walls. Sequential contraction of the constrictor muscles of the pharynx from above downward propels the bolus downward. The volume of the pharyngeal cavity reduces due to decrease in vertical pharyngeal length. The constrictor muscles contract involuntarily, but their actions are coordinated via the pharyngeal plexus. The duration of this phase is about 1 s.

24. Esophageal Phase The esophageal phase begins when the food bolus enters the esophagus. The esophagus is made up of smooth and striated muscle and is innervated by the esophageal plexus of nerves. The upper esophageal sphincter (UES) is in a state of constant contraction. The UES opens up to allow the passage of the food bolus into the esophagus. Impaired UES opening can lead to food retention in the piriform sinuses and hypopharynx, increasing the risk of aspiration following a swallow. Factors responsible for the opening of the UES are : Cricopharyngeus muscle relaxation (usually prior to the arrival of the food bolus and UES opening) Suprahyoid and thyrohyoid muscle contraction, which results in an anterior pull on the hyoid bone and the larynx, thus opening the UES Mechanical pressure offered by the bolus

25. The lower esophageal sphincter, which is also contracted at rest (which helps in prevention of gastric reflux), relaxes when the food bolus reaches it. The bolus is transported by a peristaltic wave through the lower esophageal sphincter into the stomach . The peristalsis in the thoracic esophagus is “true peristalsis” regulated by the autonomic nervous system. The peristaltic wave consists of an initial wave of relaxation that accommodates the bolus, followed by a wave of contraction that propels it. During this phase, the soft palate is lowered by the relaxation of the tensor and levator palatine muscles, the hyoid drops down, the epiglottis goes back to its original position, and the laryngeal vestibule opens.

26. Electromyographic analysis of the oral phase of swallowing in subjects with and without atypical swallowing: A case-control study Giacomo Begnoni , Maria Cadenas de Llano- Pérula , Guy Willems , Gaia Pellegrini , Federica Musto , Claudia Dellavia Background Swallowing is a complex physiologic function developing mostly in the first years of life. After 6 years old, if mature deglutition is not achieved, swallowing persists as “atypical swallowing” (AS). Objective The aim of this study was to detect any electromyographical differences in the muscular activation pattern in patients with and without AS. Materials and methods 38 adolescents and young adults were selected for this study: 20 with atypical swallowing (AS group) and 18 without (C group). Standardised surface electromyographic analysis was performed by the same operator to detect the activity of masseter (MM), temporalis (TA) and submental (SM) muscles.

27. Results When compared to controls, AS patients showed a significantly longer duration of activity for each couple of muscles and for the whole duration of swallowing act ( P  < 0.0001) as well as lower intensity of the SM activity ( P  < 0.05) than controls. Within the AS and C groups, masticatory muscles (MM and TA) showed lower duration of activation ( P  < 0.01) and lower intensity of the spike ( P  < 0.0001) than SM. Within the C group, masticatory muscles also reached their activation spike earlier (1-way ANOVA,  P  < 0.01) than SM. Conclusion Two different muscular performance models have been defined: patients with AS showed a longer activity of all the muscles involved with a lower intensity of SM activity than that of controls.

28. Automatic Detection of the Pharyngeal Phase in Raw Videos for the Videofluoroscopic Swallowing Study Using Efficient Data Collection and 3D Convolutional Networks Jong Taek Lee, Eunhee Park, Tae-Du Jung, 2019 Videofluoroscopic swallowing study (VFSS) is a standard diagnostic tool for dysphagia. To detect the presence of aspiration during a swallow, a manual search is commonly used to mark the time intervals of the pharyngeal phase on the corresponding VFSS image. In this study, we present a novel approach that uses 3D convolutional networks to detect the pharyngeal phase in raw VFSS videos without manual annotations. For efficient collection of training data, we propose a cascade framework which no longer requires time intervals of the swallowing process nor the manual marking of anatomical positions for detection. For video classification, we applied the inflated 3D convolutional network (I3D), one of the state-of-the-art network for action classification, as a baseline architecture. We also present a modified 3D convolutional network architecture that is derived from the baseline I3D architecture. The classification and detection performance of these two architectures were evaluated for comparison. The experimental results show that the proposed model outperformed the baseline I3D model in the condition where both models are trained with random weights. We conclude that the proposed method greatly reduces the examination time of the VFSS images with a low miss rate.

29. Functional endoscopy in neurogenic dysphagia: a feasibility study focusing on the esophageal phase of swallowing Jan Rückert , Philipp Lenz, Hauke Heinzow , Johannes Wessling , Tobias Warneck ,  Ingo F. Herrmann , Michael Strahl , Frank LenzeTobias Nowacki , Dirk Domagk, 2021 Background and study aims  Due to demographic transition, neurogenic dysphagia has become an increasingly recognized problem. Patients suffering from dysphagia often get caught between different clinical disciplines. In this study, we implemented a defined examination protocol for evaluating the whole swallowing process by functional endoscopy. Special focus was put on the esophageal phase of swallowing. Patients and methods  This prospective observational multidisciplinary study evaluated 31 consecutive patients with suspected neurogenic dysphagia by transnasal access applying an ultrathin video endoscope. Thirty-one patients with gastroesophageal reflux symptoms were used as a control group. We applied a modified approach including standardized endoscopic positions to compare our findings with fiberoptic endoscopic evaluation of swallowing and high-resolution manometry. The primary outcome measure was feasibility of functional endoscopy. Secondary outcome measures were adverse events (AEs), tolerability, and pathologic endoscopic findings.

30. Results  Functional endoscopy was successfully performed in all patients. No AEs were recorded. A variety of disorders were documented by functional endoscopy: incomplete or delayed closure of the upper esophageal sphincter in retroflex view, clearance disturbance of tubular esophagus, esophageal hyperperistalsis, and hypomotility. Analysis of results obtained with the diagnostic tools showed some discrepancies. Conclusions  By interdisciplinary cooperation with additional assessment of the esophageal phase of deglutition using the innovative method of functional endoscopy, the diagnosis of neurogenic disorders including dysphagia may be significantly improved, leading to a better clinical understanding of complex dysfunctional patterns. To the best of our knowledge, this is the first study to show that a retroflex view of the ultrathin video endoscope within the esophagus can be safely performed.