How fluid dynamics and transport shaped the structure of our lungs in the course of evolution

Oct 04, 2013

Two French physicists, Bernard Sapoval and Marcel Filoche from École Polytechnique in Palaiseau, France, suggest in a study published in European Physical Journal E how evolution has shaped our lungs through successive optimisations of physical parameters such as conservation of energy and speed of delivery.

Our consists of a bronchial tree designed to transport air through the lungs combined with an alveolar system designed to capture the oxygen. Both are subjected to different type of optimisations. Only tree-like structures, the paper shows, are able to efficiently feed organs above a small size, below which organs are solely fed by diffusion. Specifically, the authors first show that energy losses of fluids during transport are minimised in a tree-like structure of fractal dimension 3. Second, they indicate that this optimised tree is also 'space-filling' to optimise proximity to the working alveolae. Third, they show that a system designed to reduce the time spent to transport fluids throughout an organ has the same fractal optimisation.

In an evolutionary perspective, the size of primitive multi-cellular species was necessarily limited by nutrients' diffusion speed. One hypothesis defended in this study is that larger primitive animals have thus been conditioned by a progressive Darwinian selection of tree-like 'space-filling' nutrient distribution systems. Then, their genetic material was ready to be shared to allow mammalian respiration. Successive inspirations and expirations cycles had to be optimised so that external air could reach the alveoli before expiration starts. This form of evolutionary tinkering, the authors believe, would have allowed the emergence of mammalian respiration-as opposed to fish-style breathing through gills.

Similarly, the paper shows that the structure of the alveolar system is indeed optimal to allow efficient transport of oxygen from the air to the blood. This new insight into the 's evolutionary process stems from the physical principles underlying the architecture of living systems.

Explore further: Tiny magnetic sensor deemed attractive

More information: B. Sapoval and M. Filoche (2013), Optimisations and evolution of mammalian respiratory systems, European Physical Journal E, DOI: 10.1140/epje/i2013-13105-1

add to favorites email to friend print save as pdf

Related Stories

Tree physics limits height and leaf size, study shows

Jan 14, 2013

(Phys.org)—Why are the leaves on the tallest trees all about the same size, and why aren't those tall trees even taller? It all has to do with basic scientific principles at work in nature, according to ...

Formula unlocks secrets of cauliflower's geometry

Oct 23, 2012

The laws that govern how intricate surface patterns, such as those found in the cauliflower, develop over time have been described, for the first time, by a group of European researchers.

Recommended for you

Particles, waves and ants

9 hours ago

Animals looking for food or light waves moving through turbid media – astonishing similarities have now been found between completely different phenomena.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.