Enron

The large intestine is called the colon, while enteron is a term for the intestine, both small and large.

hydra has no specialized respiratory organs and exchanges of gases take place via simple diffusion from surface lining of the enteron on so in this way the surface lining of enteron acts as an efficient respiratory surface

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern ENT-R-N. That is, seven letter words with 1st letter E and 2nd letter N and 3rd letter T and 5th letter R and 7th letter N. In alphabetical order, they are:

enteron

Dysentery: Inflammation of the intestine, often with pain, diarrhea, bloody stools, etc. It is usually caused by infestation of the bowel by an ameba. Dysentery can be fatal, usually due to severe dehydration. Treatment includes rapid rehydration, sometimes via IV, and medication. From the Greek "dys-" meaning "abnormal or painful" + "enteron" meaning "intestine" = abnormal or painful intestine.