Nouns used in singular and plural. Which phrase is correct - the class was or the class were? Is the word class a singular noun or a plural noun? This question cannot be answered with Yes or No. Use the singular if you see the class as a group of students. Use the plural if you see the class as single students. In British English the plural is used more often than in American English. There are more words which can be singular or plural nouns: army.
In much of a digestive tract such as the human gastrointestinal tract, smooth muscle tissue contracts in sequence to produce a peristaltic wave, which propels a ball of food (called a bolus while in the esophagus and upper gastrointestinal tract and chyme in the stomach) along the tract. The primary peristaltic wave forces the bolus down the esophagus and into the stomach in a wave lasting about 8â9 seconds. 2  The wave travels down to the stomach even if the bolus of food descends at a greater rate than the wave itself, and continues even if for some reason the bolus gets stuck further up the esophagus.
1 Peristaltic contractions are always preceded by inhibition that, in the case of primary peristalsis, is called deglutitive inhibition. 2  Peristalsis in the striated muscle part of the esophagus is dependent on central mechanisms, involving sequential activation of vagal lower motor neurons in the vagal nucleus ambiguus.sophageal peristalsis consists of sequential contraction of the circular muscles of the muscularis propria, which is largely mediated by acetylcholine. This sequential contraction serves to occlude the esophageal lumen and push the bolus aborally.