Morphometry and residual strain in porcine ureter

Recent studies on blood vessels, the heart, trachea and esophagus have show n that these organs in the zero-stress state are not closed circular cross- sections of rings, but open sectors. Any analysis of stress and strain must begin with organs in the zero-stress state. This report presents data on m orphometry of the zero-stress and no-load states of the porcine ureter, and on residual strains and opening angles. The zero-stress state of the urete r is demonstrated by cutting the ureter into rings and cutting the rings in to sectors; each sector is characterized by an opening angle. The outer and inner circumferences, the cross-sectional area of the ureteral wall and th e number of buckles showed axial variation, with the highest values proxima lly in the meter. Residual strain in the circumferential direction was sign ificant, but showed no axial variation. The opening angles were approximate ly 30 degrees at the most distal and proximal sites and approximately 90 de grees in mid-ureter. The opening angle showed positive correlation to the w all thickness in the zero-stress state, residual strain at the outer circum ference and negative correlation to the length of the outer circumference i n the zero-stress state. Residual strains must be taken into account when s tudying physiological problems in which the stresses and strains are import ant, e.g. the urine transport function of the ureter.