The stomach has three types of contractions: There are rhythmic, 3 per minute, synchronized contractions in the lower part of the stomach, which create waves of food particles and juice which splash against a closed sphincter muscle (the pyloric sphincter) to grind the food into small particles.
7 What is the gestation period, how many babies do they have, and when are they weaned? 1  The gestation period for rats is 19â22 days, for mice it is 17â21 days.  Rats and mice average 8â12 babies in a litter, but can have as few as 1 or as many as 20.
According to a University of Michigan resource on breeding mice for laboratory purposes, a female mouse can give birth to between four and eight litters each year. Each litter consists of an average of between six to eight mice. A female mouse reaches sexual maturity at between 6 and 8 weeks old. The gestation period for a litter typically lasts between 19 and 21 days. Mice are very common in laboratory research, especially in genetics, in part because of this quick generation time, but this quality also makes them a pervasive pest animal.