Biomechanics of Swallowing

Feeding

• setting up, arranging, and bringing food or fluid from the container

Eating

• keeping or manipulating food or fluid in the mouth

Deglutition

• movement of solid or liquid bolus towards the esophagus

• Moving food from mouth to the stomach

Swallowing Reflex

• stimulated when food bolus is pushed into the oropharynx

• activated by receptors on posterior part of oral cavity and oropharynx

• protects respiratory tract by cleaning nasopharynx and oropharynx, and closing the larynx and nasopharynx

Gag reflex

• contraction of pharynx muscles when they are stimulated

• prevents aspiration of food particles

cough reflex

• last line of defense for the larynx is forcefully coughing out materials and manages to slip into the vocal folds and below

Aspiration

• entry of material onto the larynx and lower respiratory tract

Oral Preparatory Phase

• food is manipulated and masticated

• bolus sis formed

• bolus is held in oral cavity

• larynx and pharynx are at rest

• voluntary

Oral Phase

• Begins when the tongue initiates posterior movement of bolus

  • bolus push backward in the groove between tongue and palate

  • soft palate moves upward

  • bulge forms on the posterior pharyngeal wall approaching rising soft palate

  • tongue pushes bolus backward into oropharynx

• Voluntary

Passavant’s ridge

• bulge formed during oral phase

Pharyngeal Phase

• begins when swallow reflex is triggered

  • bolus passes between the anterior faucial arches

  • receptors at posterior wall is stimulated

  • swallow center receives sifnals

  • swallow reflex is triggered

• Reflex/involuntary

Velopharyngeal Closure

• soft palate is drawn upward to contact the passavant’s ridge

• roof of tongue moves slightly forward

• pharyngeal wall draws upward over bolus

Hyolaryngeal elevation

• bolus reaches the valleculae

• hyoid bone and loarynx move forward and up

• epiglottis tips over the larynx

• bolus flows in 2 streams aqound the epiglottis to go to the pyriform sinus

• stream unite and enter esophagus

• soft palate is pulled down to approximate root of tongue

• oropharyngeal cavity is closed with the contraction of upper esophageal sphincter

• aryepiglottic and ventricular folds approximates

• larynx completely closes

Progressive pharyngeal contraction

• segmental and sequential contraction of pharyngeal wall

• guides bolus efficiently to the upper esophageal sphincter

UES Relaxation

• permits entry of bolus into the esophagus

• Factors:

  • cricopharyngeus muscle relaxes

  • suprahyoid and thryrohyoid muscle relaxes

  • pressure of descending bolus

esophageal phase

• structures return to resting position

  • epiglottis

  • hyoid and larynx

  • soft palate

• Upper esophageal sphincter closes

• esophageal peristalsis

• Lower esophageal sphincter relaxes

• Reflex/involuntary

Esophageal Peristalsis

• stripping action

• systematic squeezing og muscle segment before bolus with simultaneous relaxation of segment preceding the bolus

Drinking

• pharyngeal response follow each swallow

• esophagus is inhibited until the last swallow

• peristalsis happens during exhalation

Belching

• prolonged drop in upper esophageal sphincter pressure

• vocal folds and arytenoids adduct

• UES opens

• small anterior hyoid movement

Pre-Retch

• diaphragm tone increases

• UES tone increases

• part of retching and vomiting

Retching

• phasic UES tone change

• diaphragm contracts during glottal closure

• UES opens

• Diaphragm relazes

• glottis opens

• UES strongly closes to prevent aspiration

Vomit expulosion

• all ues muscles relax

• UES is pulled open by hyoid muscles

• stomach contents expelled with contraction of the diaphragm

• airway protection: activation of laryngeal adductors

Aspiration

• entry of materials into the larynx and lower respiratory tract

• symptoms: coughing or choking

• can be silent too

Oral

Dysfunction:

• Aspiration before swallow

• nasal regurgitation