What's hair and bone doing in my ovary?

Torsion of the ovary (right) due to a dermoid cyst is a medical emergency and requires immediate surgery. — Photos: Dr S. SELVA

Whenever I tell a patient that the dermoid cyst in her ovary contains hair, teeth, bone, brain tissue, etc, I usually get a confused look.

The first question I will inevitably be asked is: “How can there be hair (or teeth or bone or so on) in a cyst in my ovary in my tummy?”