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.
1 Pyloric antrum: It is the first section of the pyloric part of the stomach that closes partially or completely from the remainder of the gastrointestinal tract during digestion. 2  It is bulgy and connects to the body of the stomach. 3  A small groove demarcates it from the second part of the aperture.