Proceedings

EPJ E Highlight - Understanding the evolution of lungs through physical principles

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Small bronchia, bronchioles (in white) and pulmonary arteries and veins in the human lung. Courtesy of E. R. Weibel

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

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

Our respiratory system 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 lung’s evolutionary process stems from the physical principles underlying the architecture of living systems.

Optimisations and evolution of mammalian respiratory systems. B. Sapoval and M. Filoche (2013), European Physical Journal E 36: 105, DOI 10.1140/epje/i2013-13105-1

This was our first experience of publishing with EPJ Web of Conferences. We contacted the publisher in the middle of September, just one month prior to the Conference, but everything went through smoothly. We have had published MNPS Proceedings with different publishers in the past, and would like to tell that the EPJ Web of Conferences team was probably the best, very quick, helpful and interactive. Typically, we were getting responses from EPJ Web of Conferences team within less than an hour and have had help at every production stage.
We are very thankful to Solange Guenot, Web of Conferences Publishing Editor, and Isabelle Houlbert, Web of Conferences Production Editor, for their support. These ladies are top-level professionals, who made a great contribution to the success of this issue. We are fully satisfied with the publication of the Conference Proceedings and are looking forward to further cooperation. The publication was very fast, easy and of high quality. My colleagues and I strongly recommend EPJ Web of Conferences to anyone, who is interested in quick high-quality publication of conference proceedings.

On behalf of the Organizing and Program Committees and Editorial Team of MNPS-2019, Dr. Alexey B. Nadykto, Moscow State Technological University “STANKIN”, Moscow, Russia. EPJ Web of Conferences vol. 224 (2019)

ISSN: 2100-014X (Electronic Edition)

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