Is "self-ownership" a valid concept?

Libertarians sometimes stress "self-ownership" -- the principle that you rightfully own yourself -- as a basis for political liberty. However, some criticize the concept of self-ownership is a stolen concept. This criticism says, "If you own X, then it means X is external to yourself. Therefore you cannot own yourself. To say you own yourself is to say that you are external to yourself. That doesn't compute!" But I thought rightful ownership referred to "rightful control." The law recognizes that people own their own hair and gametes and bone marrow, and therefore have a right to sell hair and sperm and eggs and marrow. These organs aren't always external to the body but are part of the body, and ownership of them refers to rightful control over them. If I should have rightful control over my own body and decisions, then do I not rightfully own myself?