PSYC340 Study Guide - Final Guide: Peristalsis, Pharynx, Medulla Oblongata
24 Jun 2018
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1. Describe the three phases of deglutition.
A. Deglutition - The movement of food from the mouth into the stomach is
achieved by the act of swallowing
A.I. Voluntary stage
A.II. Swallowing starts when the bolus is forced to the back of the oral cavity
and into the oropharynx by the movement of the tongue upward and
backward against the palate; these actions constitute
the voluntary stage of swallowing
A.III. Pharyngeal stage
A.IV. With the passage of the bolus into the oropharynx, the involuntary
pharyngeal stage of swallowing begin
A.V. Deglutition centre
A.VI. The bolus stimulates receptors in the oropharynx, which send impulses to
the deglutition center in the medulla oblongata and lower pons of the
brain stem. The returning impulses cause the soft palate and uvula to
move upward to close
off the nasopharynx, which prevents swallowed foods and liquids from
entering the nasal cavity. In addition, the epiglottis closes off the opening
to the larynx, which prevents the bolus from entering the rest of the
respiratory tract. The bolus moves through the oropharynx and the
laryngopharynx. Once the upper esophageal sphincter relaxes, the bolus
moves into the esophagus.
A.VII. Esophageal stage
A.VIII. The esophageal stage of swallowing begins once the bolus enters the
esophagus. During this phase, peristalsis, a progression of coordinated
contractions and relaxations of the circular and longitudinal layers of the
muscularis, pushes the bolus onward
A.IX. Esophageal stage of deglutition
A.X. 1 In the section of the esophagus just superior to the bolus, the circular
muscle fibers contract, constricting the esophageal wall and squeezing
the bolus toward the stomach.
A.XI. 2 Longitudinal fibers inferior to the bolus also contract, which shortens
this inferior section and pushes its walls outward so it can receive the
bolus. The contractions are repeated in waves that push the food toward
the stomach. Steps 1 and 2 repeat until the bolus reaches the lower
esophageal sphincter muscles.
A.XII. 3 The lower esophageal sphincter relaxes and the bolus moves into the
stomach.
A.XIII. Peristalsis – contractions
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Document Summary
Describe the three phases of deglutition, deglutition - the movement of food from the mouth into the stomach is achieved by the act of swallowing. Swallowing starts when the bolus is forced to the back of the oral cavity and into the oropharynx by the movement of the tongue upward and backward against the palate; these actions constitute the voluntary stage of swallowing. With the passage of the bolus into the oropharynx, the involuntary. The bolus stimulates receptors in the oropharynx, which send impulses to the deglutition center in the medulla oblongata and lower pons of the brain stem. The returning impulses cause the soft palate and uvula to move upward to close off the nasopharynx, which prevents swallowed foods and liquids from entering the nasal cavity. In addition, the epiglottis closes off the opening to the larynx, which prevents the bolus from entering the rest of the respiratory tract. The bolus moves through the oropharynx and the laryngopharynx.
