Naked Science Forum

Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: cheryl j on 06/10/2013 00:56:35

Title: Why do reptiles have a physiological vascular shunt?
Post by: cheryl j on 06/10/2013 00:56:35

I was looking at this diagram I use in class that compares circulatory systems of different animals. The reptile one is odd. I can't think of a reason for this shunt that appears to pump a portion unoxygenated blood back into the system. Does anyone know? I hope you can see the attached picture.

Title: Re: Reptile circulatory systems
Post by: CliffordK on 06/10/2013 02:12:07

It looks like your amphibians should look more like this with a 3 chamber system.

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.baileybio.com%2Fplogger%2Fimages%2Fap_biology%2Fanimal_diversity_project_-_must_cite_your_textbook_%2Fcirculatory_system_-_fish_vs_reptile.jpg&hash=9ea7275cea342d6481843c2005e1bec8)

Apparently reptiles will have either 3 chamber hearts (like amphibians) or 4 chamber hearts (like mammals).   

The pressure difference between the two chambers likely is related to the height of the animals.  Reptiles are typically quite short in statue, so pressures may be close to equal between the pulmonary and systemic parts of the circulatory system. 

A shunt like you're showing may help equalize flow and pressure.  In humans (4 chamber heart), the pulmonary side must have essentially exactly the same flow as the aortic side, but at a much lower pressure. 

The shunt may make the balance between the two sides much easier to maintain.