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.
The average life span of a rat is 2 years to 5 years. The absolute minimum is 1 year and some people say rats live from 1 to 1.5 years old, but that isn't true. They live up tâ¦o 5 years depending on how well you take care of them and if they were born with a disease or got one.