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.
The wavelike contractions of the smooth muscle in the  gastrointestinal system are called peristalsis. The purpose of  peristalsis is to push boluses of food along the gastr â¦ ointestinal  tract.