Dog bladder pressure-volume relation determined from isolated strip of wall muscle, force-length curve

UNDER appropriate conditions, isolated strips of wall muscle from the urinary bladder can be made to contract actively with electrical stimulation. Experiments were conducted to determine the force-length property of muscle strips of known dimension. Also pressure-volume data were taken from intact bladders with and without bilateral pelvic nerve stimulation. The force-length determination of the muscle strip and the pressure-volume data of the intact bladder were then related by the “modified” Laplace's law. The examined relation is Q δA B = πR 2P, where P and Q denote the radial and circumferential tensions; δA B represents the cross-sectional area of the bladder wall in the great circle and R equals radius derived from the content volume.