What can sharks teach us about our hearts?

This time of year, it's hard to escape sharks – on TV at least. But perhaps that heartbeat-like theme from "Jaws" – ba-dump, ba-dump – has you wondering, "What might I learn about my own heart from a shark?"

Strap on your scuba gear, because we are diving into that very topic.

You might assume that sharks and humans do not have much in common at heart. After all, our last shared link on the evolutionary tree was perhaps 400 to 450 million years ago.

But shark hearts and human hearts are similar in at least one basic way, said Dr. Georgina Cox, an assistant professor at Washington State University Vancouver. "Basically, the heart is a pump, no matter what species you look at."

And that pump isn't just delivering oxygen-rich blood, said Cox, a comparative cardiovascular physiologist. "It unites all of our bodily systems," helping to remove waste and deliver hormones that enable organs to communicate with one another.

Cox teaches human anatomy and biochemistry while studying fish cardiovascular systems and how fish respond to stressors such as increased temperatures and pollution. In both sharks and humans, she said, the heart never stops beating. "And like us, if a fish's heart stops working, that's it," she said.

But while they are alike in function, shark and human hearts differ in form, said Dr. Jules Devaux, a research fellow in the School of Biological Sciences at the University of Auckland in New Zealand.

Humans and other mammals have a four-chambered heart – two upper chambers, called atria, and two lower chambers, or ventricles – that push blood from the heart to our lungs to get oxygen, then back to the heart, then out to the body.

Sharks, like other fish, have what is usually described as a two-chambered heart – one atrium and one ventricle. Inside a rigid,...