Understanding The Normal Swallow Flashcards
What cranial nerves are involved in swallow
Trigeminal Facial Glossopharyngeal Vagus Accessory Hypoglossal
What are the three steps in the basic neurological process of the swallow?
Step 1 - cortical recognition of food
Step 2 - food processed and activates sensory receptors
Step 3 - complex neural network generates a swallow response
What are the stages of the swallow?
"Pre oral anticipatory phase" Oral preparatory phase Oral stage Pharyngeal stage Oesophageal phase
what does the oral preparatory phase involve?
The manipulation of food or liquid in order to form a cohesive bolus for swallowing
Is airway open in oral prep phase?
Yes
What are the key structures involved in the oral prep phase?
Lips
Tongue
Teeth and jaw
Cheek
What is the oral stage?
The voluntary stage, which begins after the bolus is prepared with the posterior propulsion of the bolus by the tongue into the oropharynx and then into the hypopharynx. Ends with the trigger of the swallow
Describe the oral stage…
The bolus is held in the mid-central groove/depression with lateral edges of tongue against the hard palate/lateral side of teeth
Lips and buccal muscles contract and velum elevates to. Closes off nasopharynx
Posterior of tongue depresses, and anterior tongue presses against hard palate propelling bolus backwards - stripping action
What are the key structures of the oral stage?
Intrinsic muscles of the tongue
Extrinsic muscles of the tongue - digastric (CNV), mylohyoid (CNV) geniohyoid (CNXII) - allow tongue to propel bolus backwards and elevate hyoid superiorly and anteriorly
What are the key structures involved in the pharyngeal phase?
Velum makes sure nasal cavity is closed
Hyoid - moves forward - as it moves, it pulls everything forward
Epiglottis - prevents food entering airway
When does the pharyngeal stage start?
When the leading edge, or ‘head’ of the bolus passes any point between the anterior faucial arches and when the tongue base crosses the lower rim of the mandible.
What happens once the pharyngeal stage is triggered?
Tongue base retraction
Velar closure
Hyoid elevates and moves anteriorly, elevating the larynx
Closure of the true vocal folds
Closure of the laryngeal entrance (False vocal folds adduct, arytenoids medialise and tilt anteriorly and epiglottic base thickens as larynx elevates)
Tongue base contact with anterior bulging of posterior pharyngeal wall
Deflection of the epiglottis over laryngeal entrance
Progressive contraction of pharyngeal constrictor muscles
Cricopharyngeal sphincter opens to allow passage of bolus
Describe the pattern of bolus flow
As the bolus is propelled from the oral cavity it passes over the depressed base of tongue - in a ramp like fashion
At the point of epiglottis/valleculae, the bolus is diverted around the larynx. At this point in 80% of normals, a liquid bolus typically divides in half at the valleculae and then travels down the the pharynx in the pyriform sinuses. Solid doesn’t split - goes down one side
The bolus then joins together at the point of the oesophagus
What facilitates bolus transit
Tongue driving pressure
Negative pressure differential created by opening of Cricopharyngeal sphincter
Contraction of pharyngeal constrictors - clearing force
What are the pressure, pumps and seals involved?
Closure of lips and tension of buccal musculature
Posterior propulsion of the bolus into the pharynx by the tongue
Closure of velopharyngeal port, plus elevation of larynx, shortening pharyngeal space
Closure of true and false vocal folds plus opening of Cricopharyngeal sphincter opening creates a pressure differential, which helps to direct the bolus through the pharynx and into the oesophagus
Pressure to the tail of the bolus caused by the base of tongue to posterior pharyngeal wall contact - ongoing downward wave of pharyngeal contraction
