One of our pathology professors told us this joke:
How do you tell an introverted pathologist from an extroverted pathologist?
The introverted pathologist stares at his shoes when he’s talking to you. The extroverted pathologist stares at your shoes when he’s talking to you.
This is cute. I’ll have to share it with my stepfather, who is a pathologist. He is an introvert married to my mother, an extrovert. 
Love,
Stacy
This classic joke also works for accountants.
Speaking of classic medical related humor, here are a few short ones:
What is the difference between the doctor and God?
God never claims he is a doctor!
Surgeons aren’t always right to, but they are never in doubt
and as my yiddisha mama told me, what do you call a Jewish boy who can’t stand the sight of blood? A psychiatrist.
Did you hear about the two chums who happen to meet in the waiting room of a psychiatrist’s office? One asks “are you coming or going?” And the other replies, " if I knew that it wouldn’t be here?"
Well you’ve been a wonderful audience but now it’s time to go. And let’s hear it for the band!