What body part is this?

teacher name the body part

Mr. Williams was teaching his biology class, and quizzing them on last night’s reading assignment.

“Shannon, can you tell me which part in the human body can expand to several times its normal size?” asked Mr. Williams.

Shannon giggled as if she were thinking of something unmentionable in class.

“Sean, can you tell me?” asked Mr. Mr. Williams.

“The Eye,” said Sean.

“That’s right,” and Mr. Williams continued, “Shannon, I’ll tell you three things that are certain.”

“First, you did not do your reading last night.”

“Second, you have a very dirty mind.”

“And Third, you are going to be VERY disappointed, and THAT’S FOR SURE.”