Americans have a nearly insatiable demand for blood.

Every two seconds, someone in the country requires a blood transfusion. And to get one they go straight to a blood bank.

But it’s a strange idea. A blood bank. Or a sperm bank. Or a breast milk bank. What kind of bank relies on donations? That’s the idea that got Kara Swanson interested in the idea, the history and the theory behind banking our precious bodily fluids. She says our current system of banking body parts isn’t just counterintuitive; it’s costing lives.

WBUR’s Sacha Pfeiffer speaks with Swanson about the thriving market in human body products, and the complicated legal and medical questions surrounding it.