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.
Life Expectancy. From birth to adult, rats take about three weeks to mature and begin fending for themselves. The rodents reach sexual maturity in about five weeks and begin mating soon after to produce the next generation to start the rat life cycle over again. Life expectancy for rats is about two to three years.