Coordination of mastication and swallowing |
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Authors: | Jeffrey B Palmer MD Nathan J Rudin MD Gustavo Lara BA Alfred W Crompton PhD |
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Institution: | (1) Department of Rehabilitation Medicine, the Swallowing Center, Johns Hopkins University, Baltimore, Maryland, USA;(2) Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University, Baltimore, Maryland, USA;(3) Good Samaritan Hospital, Baltimore, Maryland, USA;(4) Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, USA;(5) Good Samaritan Professional Office Building, Rm 303, 5601 Loch Raven Boulevard, 21239 Baltimore, MD, USA;(6) Present address: Francis Scott Key Medical Center, Baltimore, MD, USA;(7) Present address: Harvard Medical School, Boston, MA, USA |
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Abstract: | The coordination of mastication, oral transport, and swallowing was examined during intake of solids and liquids in four normal
subjects. Videofluorography (VFG) and electromyography (EMG) were recorded simultaneously while subjects consumed barium-impregnated
foods. Intramuscular electrodes were inserted in the masseter, suprahyoid, and infrahyoid muscles. Ninety-four swallows were
analyzed frame-by-frame for timing of bolus transport, swallowing, and phases of the masticatory gape cycle. Barium entered
the pharynx a mean of 1.1 s (range −0.3 to 6.4 s) before swallow onset. This interval varied significantly among foods and
was shortest for liquids. A bolus of food reached the valleculae prior to swallow onset in 37% of sequences, but most of the
food was in the oral cavity at the onset of swallowing. Nearly all swallows started during the intercuspal (minimum gape)
phase of the masticatory cycle. Selected sequences were analyzed further by computer, using an analog-to-digital convertor
(for EMG) and frame grabber (for VFG). When subjects chewed solid food, there were loosely linked cycles of jaw and hyoid
motion. A preswallow bolus of chewed food was transported from the oral cavity to the oropharynx by protraction (movement
forward and upward) of the tongue and hyoid bone. The tongue compressed the food against the palate and squeezed a portion
into the pharynx one or more cycles prior to swallowing. This protraction was produced by contraction of the geniohyoid and
anterior digastric muscles, and occurred during the intercuspal (minimum gape) and opening phases of the masticatory cycle.
The mechanism of preswallow transport was highly similar to the oral phase of swallowing. Alternation of jaw adductor and
abductor activity during mastication provided a framework for integration of chewing, transport, and swallowing. |
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Keywords: | Deglutition Mastication Physicology Oral cavity Pharynx Deglutition disorders |
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