Scaling laws of vascular trees: of form and function

• Published in: American journal of physiology. Heart and circulatory physiology 2006-02, Vol.290 (2), p.H894-H903
• Main Author: Kassab, Ghassan S
• Format: Article
• Language: English
• Subjects: Animals; Blood Vessels - anatomy & histology; Blood Vessels - growth & development; Blood Vessels - metabolism; Blood Vessels - physiology; Energy Metabolism; Homeostasis; Humans; Models, Cardiovascular; Organ Size; Regional Blood Flow
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00579.2005

Department of Biomedical Engineering, University of California, Irvine, California Submitted 1 June 2005 ; accepted in final form 26 August 2005 The branching pattern and vascular geometry of biological tree structure are complex. Here we show that the design of all vascular trees for which there exist morphometric data in the literature (e.g., coronary, pulmonary; vessels of various skeletal muscles, mesentery, omentum, and conjunctiva) obeys a set of scaling laws that are based on the hypothesis that the cost of construction of the tree structure and operation of fluid conduction is minimized. The laws consist of scaling relationships between 1 ) length and vascular volume of the tree, 2 ) lumen diameter and blood flow rate in each branch, and 3 ) diameter and length of vessel branches. The exponent of the diameter-flow rate relation is not necessarily equal to 3.0 as required by Murray's law but depends on the ratio of metabolic to viscous power dissipation of the tree of interest. The major significance of the present analysis is to show that the design of various vascular trees of different organs and species can be deduced on the basis of the minimum energy hypothesis and conservation of energy under steady-state conditions. The present study reveals the similarity of nature's scaling laws that dictate the design of various vascular trees and the underlying physical and physiological principles. design; morphometry; minimum energy; shear stress; Murray's law Address for reprint requests and other correspondence: G. S. Kassab, Dept. of Biomedical Engineering, Univ. of California, Irvine, 204 Rockwell Engineering Ctr., Irvine, CA 92697-2715 (e-mail: gkassab{at}uci.edu )