Since this is in the health section, I think you are referring to an "esophagus," which is the muscular passage connecting the mouth and throat with the stomach. Here's more info from csmc.edu: "At each end (of the esophagus), the tube is closed by the contraction of special muscles called sphincters. The esophagus and sphincter muscles are designed to move what is swallowed to the stomach. They also prevent stomach contents from moving back up into the esophagus and breathing passages. Food that enters the esophagus is squeezed down to the stomach by a special muscle contraction called peristalsis. Peristalsis is like placing your fingers at the closed end of a tube of toothpaste and using them to squeeze all the toothpaste out the open end. The sphincter muscle at the lower end of the esophagus opens so the food can enter the stomach. Once the food is in the stomach, the muscle closes so the food and stomach acid cannot move back up the esophagus. "

There are some disorders that cause your esophagus not to open and close properly, which may make it difficult to swallow (and in some cases cause choking). I'll provide a list of links so you can learn more:

• Esophageal Spasm: http://www.webmd.com/digestive-disorders/tc/esophageal-spasm-topic-overview
• Barrett's Esophagus: http://www.webmd.com/heartburn-gerd/baretts-esophagus
• Cancer of the Esophagus: http://www.webmd.com/cancer/cancer-of-the-esophagus
  
• Achalasia: http://www.csmc.edu/5286.html
• tracheo-esophageal fistula: http://www.csmc.edu/5802.html
• Gastroesophageal reflux disease: http://www.csmc.edu/5543.html
• Esophagitis: http://www.csmc.edu/5650.html
• Allergic Reactions (throat closes up): http://www.pdrhealth.com/disease/disease-mono.aspx?contentFileName=BHG01AL02.xml&contentName=Allergic+reactions&contentId=05&sectionMonograph=ht2

I hope this helps!

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