This book addresses a simple question: Are animals designed economically? The pronghorn can run at speeds of up to 60 kilometers an hour and can maintain this speed for nearly a full hour. Clearly, the form of this elegant animal is beautifully matched to the function it needs to perform.
This is symmorphosis. The theory of symmorphosis predicts that the size of the parts in a system must be matched to the overall functional demand. Moreover, it predicts that animals must provide their complex systems with a functional capacity that can cope with the highest expected functional demands, possibly including some safety margin to prevent the system from failing when it is overloaded. In Symmorphosis, Ewald Weibel tests these predictions by working out the quantitative relations between form and function.
Physiologists will value this book because Weibel shows them that morphological information can be as quantitative as physiological data. Anatomists will value the book for its demonstration that advanced integrative physiology crucially depends on adequate but rigorously quantitative and testable information on structural design. Finally, anyone interested in the origins of the diverse forms of animals will be fascinated by Weibel's demonstrations that show how animals as different as shrews, pronghorns, dogs, goats – even humans – all develop from essentially the same blueprint by variation of design. This is a hidden beauty of the animal kingdom, which can be uncovered by a rigorous investigation of the quantitative relations of form and function.
Preface
1. Form and Function
The Relation of Form and Function
Adaptation of Function as a Design Principle
Integration of Function as a Design Principle
Economy as a Design Principle
The Principle of Symmorphosis
2. Cells and Tissues: Oxidative Metabolism in Muscle
Energy Supply and Mitochondria
Is Mitochondrial Structure Matched to the Demand for Oxidative Energy?
Testing for a Quantitative Match of Form and Function in Muscle Mitochondria
Is 6VO2 Related to V(mi) in Exercising Muscle Cells?
Natural Variation in Energy Demand and Mitochondria
Are Muscle Capillaries Adjusted to Mitochondrial Oxygen Needs?
Symmorphosis in the O2 Pathway in Muscle
3. Muscle: Supplying Fuel and Oxygen to Mitochondria
Differences between Oxygen and Fuel Supply
Variations in Fuel Supply to Mitochondria in Working Muscle Cells
Partitioning of Fuel Consumption between Glucose and Fatty Acids
Estimating the Capillary Supply of Substrates
Revising the Model for Capillary Oxygen and Substrate Supply
Fuel Supply from Capillaries versus Intracellular Stores
Conclusions on Form and Function in Muscle Cells and Tissue
4. Organ Design: Building the Lung as a Gas Exchanger
Modeling Gas Exchange in the Lung
A Large Surface and a Thin Barrier Determine the Gas Exchange Capacity of the Lung
The Diffusing Capacity of the Human Lung
How Much Lung Diffusing Capacity Do We Really Need?
The Gas Exchanger of the Most Athletic Animal
The Effect of Reducing the Gas Exchanger
Conclusion
5. Problems with Lung Design: Keeping the Surface Large and the Barrier Thin
A Fiber Continuum Supports Parenchymal Structures
Controlled Surface Tension Determines Parenchymal Mechanics
Keeping the Barrier Dry and Thin
Conclusion
6. Airways and Blood Vessels: Ventilating and Perfusing a Large Surface
Morphogenesis of Airways, Vessels, and Gas Exchanger
Designing the Airway Tree for Efficient Ventilation
Are Airways Designed as Fractal Trees?
Conclusion
7. The Pathway for Oxygen: From Lung to Mitochondria
Testing the Hypothesis of Symmorphosis
The Strategy: Exploiting Comparative Physiology
The Model and Predictions
Testing the Respiratory System for Symmorphosis
Does Symmorphosis Prevail in the Respiratory System?
8. Adding Complexity in Form and Function: The Combined Pathways for Oxygen and Fuels
Strategies for Oxygen and Fuel Supply
Design of the Fuel Supply Pathway
Design of Nutrient Uptake Systems
The Substrate Pathways for Fueling Muscle Work
The Test of Symmorphosis
On Symmorphosis in Complex Pathways
9. Symmorphosis in Form and Function: Concepts, Facts, and Open Questions
How to Perform a Test of Symmorphosis: Future Prospects
Conclusions
References and Further Reading
Credits
Index
Ewald R. Weibel is Professor of Anatomy, University of Bern, Switzerland.
"Weibel's treatment serves as an excellent introduction to mammalian respiratory and exercise physiology. His writing is as concise and linearly organized as the pathway for oxygen that he so eloquently describes [...] Weibel has done an admirable job of describing both morphology and functional performance."
– Robert Dudley, American Scientist
"Symmorphosis is (and I use the term advisedly) magisterial: the best description anywhere of a provocative and creatively stimulating research approach to a large number of very important basic questions in animal – more specifically mammalian and human – anatomy, physiology, and evolution. This book is synthetic in the best sense of that word."
– Malcolm S. Gordon, University of California, Los Angeles