[In vitro studies into interdependence of volume and pressure in non-pregnant human uterus (author's transl)]

Abstract

This paper follows on studies undertaken earlier into physiological and pharmacological aspects relating to the nonpregnant uterus of women in sexual maturity. The interdependence between volume and pressure is described with reference to a known model of the non-pregnant uterus. -- Uterus expansiveness in the second phase of the cycle was found to be larger than that in the first phase. The interdependence between volume and intra-uterine pressure is of linear nature. Intramural pressure and changes in perfusion pressure are but negligibly affected by volume enlargement and expansion of the uterine cavity and not even by intrauterine pressure which increase beyond 400 mmHg. This is attributable to a number of factors, borne out by both Laplace's formula and the authors' own findings, such as a relatively small volume, small radius, and larger wall thickness of the non-pregnant uterus. Optimum contractility depends on optimum volume, the latter being typical of the individual uterus. Excessive volume is likely to lead to higher intra-uterine and intramural tonus. Discoordination of contractility, rise in tonus, alteration of the contraction amplitude, and rise in frequency are consequences. Both change in volume and passive expansiveness of the uterus will not really affect blood supply unless major changes occurred to intramural pressure (in excess of something between 70 and 80 mmHg) to obstruct the blood flow. High intramural pressures are required because of the small volume of the nonpregnant uterus, in order to cause contractility strong enough to eject the content of the uterus, for example, in menstruation.