Introduction to Swallowing

• Dysphagia Institute
• Dysphagia Resource Center
• American Academy of Otolaryngology - Head and Neck Surgery Public Service Brochure

Terminology

• Dysphagia-difficulty of swallowing
• Feeding - term is limited to the placement of food in the mouth, the manipulation of food in the oral cavity prior to the initiation of the swallow, including mastication if necessary, and the oral stage of the swallow when the bolus is propelled backward by the tongue.
• Swallowing - Refers to the entire act of deglutition from placement of food in the mouth through the oral and pharyngeal stages of the swallow until the material enters the esophagus through the cricopharyngeal juncture.
• Deglutition - process of swallowing
• Oropharyngeal Dysphagia
• Esopharyngeal Dysphagia

Anatomic Structures (Groher, Fig 1.1)

Mayo Glossary

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• Oral Cavity
• Lips anteriorly
• teeth
• hard palate
• soft palate
• uvula
• mandible
• lower jaw
• floor of mouth tongue
• faucial arches
• palatine tonsils
• Pharynx - Three pharyngeal constrictors (Groher, fig 1.4)
  • Superior pharyngeal constrictor - The elevation and contraction of the velum results in the complete closure of the velopharyngeal port, this action is facilitated by the contraction of the spc, which narrow the pharynx.
  • Medial and inferior pharyngeal constrictors-Initiation of pharyngeal peristalsis occurs. The bolus is carried by sequential peristaltic action of the middle and inferior pharyngeal constrictors into and through the pharynx to the cricopharygneal sphincter.
• thyroid cartilage - fibers of the inferior constrictor attach to the sides of the thyroid cartilage anteriorly, a space is formed between these fibers and the sides of the thyroid cartilage.
• pyriform sinuses - These spaces are known as the pyriform sinuses. These end inferiorly at the cricopharyngeus muscle, which is the most inferior structure of the pharynx and serves as the valve at the top of the esophagus. Pharyngeal constrictors insert into throid cartilage anteriorly to form pyriform sinuses
• pharyngoesphageal sphincter or juncture (P-E segment) upon contraction prevents air from entering the esophagus during respiration and material from refluxing back up the esophagus and into the pharynx.
• larynx
  • vocal folds
    • superior view
  • Structures
  • vocal fold closure
• epiglottis (Logemann, fig 2-5) - The topmost structure of the larynx is the epiglottis, which rests against the base of the tongue. The wedge-shaped space formed between the base of the tongue and epiglottic is the valleculae. The valleculae and the pyriform sinuses are known as the pharyngeal recesses or side pockets, into which food may fall and reside before or after the swallowing reflex triggers.
• trachea
  • structure
• Esophagus - consists of a hollow muscular tube 23 to 25 cm long with a sphincter at each end.

Physiology - UMD Tutorial

• Oral Preparatory Phase
  • Movement patterns depend on consistency of material swallowed
  • Liquid Bolus has a certain degree of cohesiveness that may be maintained as bolus is held between tongue and anterior hard palate.
  • Lip Closure
  • Facial tone helps with labial seal.
  • Rotary, lateral jaw movement
  • Rotary, lateral tongue movement
  • Anterior pulling of soft palate and rests against the back of the tongue, which is elevated serving to keep material in the oral cavity.
• Oral Phase (1 sec)
  • Intact labial seal
  • Anterior to posterior tongue movement
• Pharyngeal Phase-Pharyngeal Response (1 sec)
  • Triggering of the swallowing response occurs at the anterior faucial arch.
    • elevation and retraction of the velum and complete closure of
    • velopharyngeal port to prevent material from entering the nasal cavity.
    • initiation of pharyngeal peristalis to pick up the bolus as it passes the anterior faucial arch and carry it by sequential peristalic (squeezing) action of the pharyngeal constrictors into and through the pharynx to the cricopharyngeal sphincter at the top of the esophagus.
    • elevation and closure of the larynx at all three sphincters (epiglottis/aryepiglottic folds, false vocal folds, and true vocal folds) to prevent material from entering the airway.
    • relaxation of the cricopharyngeal sphincter to allow material to pass from pharynx into the esophagus.
    • laryngeal elevation and cricopharngeus relaxation
  • Transit time can be measuered from the point where the bolus moves from the point at which the reflex is triggered at the anterior faucial arch through the cricopharyngeal juncture into the espohagus.
• Esophageal Phase (8-20 sec) transit times can be measured from the point where the bolus enters the esophagus at the crico-esophageal juncture until it passes into the stomach at the gastro-esophageal juncture.

Neural Regulation of Swallowing

• Swallowing is initiated by sensory impulses transmitted as a result of stimulation of receptors on the fauces, tonsils, soft palate, base of the tongue, and posterior pharyngeal wall.
• Sensory impulses reach the brainstem primarily through the 7th, 9th, and 10 cranial nerves, while the efferent (motor) function is mediated through the 9th, 10th, 12th cranial nerves.Cricopharyngeal sphincter opening is reflexive, relaxation occurring at the time when the bolus reaches the posterior pharyngal wall prior to reaching this sphincter.
• Cranial Nerves
  • CN V -- Trigeminal
    • contains both sensory and motor fibers that innervate the face
    • important in chewing
  • CN VII -- Facial
    • contains both sensory and motor fibers
    • important for sensation of oropharynx & taste to anterior 2/3 of tongue
  • CN IX -- Glossopharyngeal
    • contains both sensory and motor fibers
    • important for taste to posterior tongue, sensory and motor functions of the pharynx
  • CN X -- Vagus
    • contains both sensory and motor fibers
    • important for taste to oropharynx, and sensation and motor function to larynx and laryngopharynx.
    • important for airway protection
  • CN XII -- Hypoglossal
    • contains motor fibers that primarily innervate the tongue

   

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  Lateral cricoarytenoid muscle and oblique interarytenoid muscles adduct (close) vocal folds.

  Posterior cricoarytenoid muscles abduct (open) vocal folds.

 http://swallow.mit.edu/swallow/movswal.htm

Table 1.6 & 1. 7 (groher)