human body part expands 5 times its normal size

Medical College Professor to a Girl Student: Which human body part expands 5 times its normal size?

Girl Student: Sir I cant answer this question, it’s too embarassing..

Professor asked the same question to a Male Student:

Male Student: It’s the Pupil of a human eye

Professor: correct

Then Professor turned to the female student & said,

listen baby, Not only your thinking is wrong but your expectations are also very high..!