THE BIOMECHANICS OF VAGINAL TISSUE AND SUPPORTING LIGAMENTS WITH SPECIAL RELEVANCE TO THE PATHOGENESIS OF FEMALE URINARY-INCONTINENCE .2.

The vagina is presented as a living organ, whose structure, elasticity and tensile properties may be altered by age, pregnancy, parturition, and surgery. An alternative concept for urodynamic pressure measureme nt is introduced, based on the Integral Theory (1; p63-67), whereby fo rces creating the pressure in the urethra as measured by a microtransd ucer, actually derive from the periurethral striated muscle (PUSM). As pressure = force/area, given that the muscle force for a given contra ction is always constant, dynamic pressure variations during manoeuvre s such as coughing, straining and 'cutting-off will vary according to the area of the urethral cavity over which the PUSM forces are applied . This area varies according to what degree of urethral closure is att ained by the closure muscles acting on the vagina. The relationship of vaginal tension to these forces is analysed with special reference to the stress extension curve of vagina, and also, the various anatomica l defects as defined by the proposed Integral Theory.