New model explains how veins grow in plants and animals

PHILADELPHIA, Oct. 3 (UPI) -- A variety of anatomical systems are governed by rules and ratios consistent throughout the animal kingdom. New research suggests one of those systems is the vascular system.

In a new study, scientists at the University of Pennsylvania have explained how the rule of "adaptive feedback" governs the development of vascular systems in both plants and animals.

Adaptive feedback describes the ability of a living organism to alter the size of a vein based on the rate of liquid flow. Greater amounts of liquid flow inspire a wider vein, while lesser amounts inspire a thinner -- and eventually closed off -- vein.

Previously, when scientists attempted to build predictive models using the rule of adaptive feedback, the results were faulty. Simulations failed to produce vascular systems resembling those found in nature.

Recently, Penn researchers realized the models were missing an important variable -- growth. When they redesigned adaptive feedback models while accounting for the growth of an organism over time, the results were much improved.

"Once I had the derivation, the rest was almost straightforward," Henrik Ronellenfitsch, a postdoctoral researcher at Penn, said in a news release. "It came as a surprise that it works as well as it does."

Ronellenfitsch works in the lab of Penn physicist Eleni Katifori, the lead author of the new study -- published this week in the journal Physical Review Letters.

Katifori believes the latest breakthrough has applications beyond biology.

"This study implies, that whenever you have a system that transports liquids, energy, and maybe other things we haven't looked at, if you have growth then you will get something close to the best possible network -- the absolute best one, not just a good one," Katifori said.

But the new model isn't perfect. Simulations fail to replicate the redundancy found in real vascular systems, a vital component of vascular systems that allows plants and animals to recover from tissue damage.

"In our model, if you cut something, everything downstream from that vein is dead," said Ronellenfitsch. "And that's not a feature that vein networks have. Real networks are highly redundant."