## Abstarct

The original law of Laplace pertains to soap bubbles, with radius *r*, and gives the relation between transmural pressure, *P* _{ t }, and wall tension, *T* _{ s }, in a thin-walled sphere as *T* _{ s } =*P* _{ t } · *r*. The law can be used, for example, to calculate tension in alveoli. This tension is directly related to surface tension and has the dimension N/m. The form of the law of Laplace most often used in hemodynamics gives the relation between transmural pressure and the stress in the wall in organs with a wall thickness *h*. We here use the Cauchy stress formulation, which is defined as the ratio of the normal (perpendicular) force acting on a surface divided by the area of the surface at its deformed configuration. Stress has the dimension N/m^{2} (see Figure in the box).

## Keywords

Circular Cylinder Fiber Stress Wall Stress Transmural Pressure Wall Tension## References

- 1.Huisman RM, Sipkema P, Westerhof N, Elzinga G, Comparison of models used to calculate left ventricular wall force.
*Med Biol Eng Comput*1980;18:133–144.PubMedCrossRefGoogle Scholar - 2.Hefner LL, Sheffield LT, Cobbs GC, Klip W. Relation between mural force and pressure in the left ventricle of the dog.
*Circ Res*1962;11:654–663.PubMedCrossRefGoogle Scholar - 3.Mirsky I, Rankin JS. The effects of geometry, elasticity, and external pressures on the diastolic pressure-volume and stiffness-stress relations. How important is the pericardium?
*Circ Res*1979;44:601–611. Review.PubMedCrossRefGoogle Scholar - 4.Arts T, Bovendeerd HHM, Prinzen FW, Reneman RS. Relation between left ventricular cavity pressure and volume and systolic fiber stress and strain in the wall.
*Biophys J*1991;59:93–102.PubMedCrossRefGoogle Scholar - 5.Love AEH.
*A treatise on mathematical elasticity*. 1952, London & New York, Cambridge University Press, third edn.Google Scholar