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Related Experiment Videos

The heart works against gravity

R S Seymour1, A R Hargens, T J Pedley

  • 1Department of Zoology, University of Adelaide, South Australia.

The American Journal of Physiology
|October 1, 1993
PubMed
Summary

The siphon principle does not aid blood flow in vertebrate circulatory systems when vessels can collapse. Gravity

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Flutter in a quasi-one-dimensional model of a collapsible channel.

Proceedings. Mathematical, physical, and engineering sciences·2014

Area of Science:

  • Cardiovascular Physiology
  • Biomechanics
  • Vertebrate Anatomy

Background:

  • Vertebrate circulatory systems are closed, with blood returning to the heart at the same level.
  • It is commonly believed the heart works against viscous resistance, not gravity, even in superior vascular loops.
  • The siphon principle is thought to assist blood flow in these superior loops.

Purpose of the Study:

  • To investigate the role of the siphon principle in blood flow within superior vascular loops.
  • To determine if vascular collapse affects the siphon principle's assistance.
  • To challenge the established understanding of gravitational effects on circulation.

Main Methods:

  • Theoretical analysis of fluid dynamics in collapsible vessels.
  • Application of the Poiseuille equation to collapsible and non-collapsible vascular segments.
  • Laboratory modeling using water flow through collapsible tubing.

Main Results:

  • The siphon principle does not assist blood flow in superior loops if descending vessels are collapsible.
  • Vascular collapse halts blood flow if central arterial pressure is insufficient to support the blood column.
  • Potential energy is lost to friction in collapsed vessels, negating siphon assistance.
  • Flow rate in partially collapsed vessels is independent of resistance.

Conclusions:

  • The siphon principle does not facilitate blood flow in superior vascular loops of vertebrates.
  • Vascular collapse, not gravity, is a critical factor limiting blood flow in these systems.
  • Previous findings may be influenced by experimental artifacts related to vessel collapsibility.
Keywords:
NASA Center ARCNASA Discipline Cardiopulmonary

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