Deglutition – a complex process

• (1) Oral Preparatory phase (does not occur in infants) – voluntary, involves mastication and mixing with saliva
• Oral sphincter – lip closure and tension
• Bolus formation – getting food into a nice little package; rotary jaw motion, lateral rolling motion of the tongue.
• Bolus positioning – getting it read for swallowing
• Tongue and cheek muscles keep food positioned over teeth
• (2) Oral phase – voluntary, positioning of bolus for entry into the pharynx. Ends when bolus reaches the palatoglossus
• Tongue genioglossus contracts to make furrow in tongue
• This stage lasts about 1 second
• (3) Pharyngeal phase –involuntary; starts when bolus reaches palatoglossus, ends when bolus reaches cricopharyngeus
• levator palatini closes the connection to nose and flattens the tongue; hyoid bone is pulled forward by the suprahyoid muscles, which also tilts epiglottis down; also get the beginning of the pharyngeal contraction
• Controlled by the medullary swallowing center, triggered reflexively by mechanical stimulation
• CN V – Sensation of the anterior tonsillar pillar is necessary
• CN VII – Vidian nerve, nerve of the pterygoid canal
• CN IX and X – innervation to the pharyngeal plexus (IX only motor to stylopharyngeus)
• Food flows around the epiglottis
• Piriform sinuses – can be a hidden source of a primary cancer (smokers and drinkers)
• Cleft palate – actual connection from oral cavity to nasal cavity (hard to suck), use special "squirt" bottle, also problems with estuation tubes and these kids get more ear infections
• Velopharyngeal insufficiency – a complication of an adenoidectomy; soft palate can’t close because there’s too much space left where adenoid patch used to be
• The nasopharynx can be closed laterally with lateral pharyngeal walls to make up for insufficiency
• In children the subglottic space is the narrowest portion of the airway, surrounded by cricoid cartilage
• Larynx is closed off too; this keeps any part of the bolus that slipped around the epiglottis out of airway. Good sensation via the superior laryngeal nerve is necessary to do this.
• (4) Esophageal phase – involuntaryt; begins once the bolus has reached the cricopharyngeus
• Upper esophageal sphincter – tonically contracted to protect the pharynx from reflux
• Smooth peristaltic esophageal contractions (enteric nervous system)
• primary peristalsis – takes 8-10 seconds for transit, occurs after central stimulation of the ENS by the medullary swallowing center
• secondary peristalsis – stimulated by mechanical distention of smooth muscle
• relaxation of the Lower Esophageal Sphincter is vagally mediated
• Problems in Esophageal Phase:
• Zenker’s diverticulum – herniation of mucosa out of cricopharyngus, contain food Þ bad breath
• intrinsic or extrinsic compression of the esophagus
• diverticulae (in the lumen of the esophagus)
• hiatal hernia