You may also have diarrhea or a fever. It is sometimes called stomach flu, but it is not the flu. Germs like viruses and bacteria can cause it. You can catch it from someone else who has it, or you can get it from food poisoning. Food poisoning can happen if you eat foods that contain harmful germs.
The circular muscle located at the entrance and exit to the stomach is called the sphincter. So for this question, you are talking about two distinct sphincters. This anatomical structure is able to open, and contract or close as needed.
deep (internal) ring opening in the transversalis fascia, superficial (external) ring opening in the aponeurosis of the external oblique muscle. What are the boundaries of the inguinal canal: anterior wall. external abdominal oblique over entire length (aponeurosis of); internal abdominal oblique on lateral one-third.