Uterine peristaltic activity during the menstrual cycle: characterization, regulation, function and dysfunction.

Unlike other smooth muscle organs, the uterine muscle was regarded to be normally functional for only a brief period, following a lengthy gestation. However, recently it has been shown that uterine peristalsis constitutes one of the fundamental functions of the non-pregnant uterus. Its morphological basis is the archimyometrium, which is the muscular component of the archimetra and which preserves a functional bipartition of the primarily unpaired uterus. Three types of uterine peristaltic contractions can be distinguished: cervico-fundal, fundo-cervical and isthmical peristaltic activity, which changes during the menstrual cycle and is controlled by the dominant ovarian structure via the secretion of sex steroids systemically and into the utero-ovarian vascular countercurrent system. Uterine peristalsis of the non-pregnant uterus is actively involved in very early reproductive processes, such as rapid and sustained directed sperm transport and high fundal implantation, as well as serving retrograde menstruation for the preservation of body iron content. Furthermore, it became apparent that hyper- and dysfunctions of this contractile activity, such as hyper- and dysperistalsis, might be causally involved in the development of pelvic endometriosis, uterine adenomyosis and infertility, as obtained from immunohistochemistry, vaginal sonography, hysterosalpingoscintigraphy and magnetic resonance imaging.