THE FINE-STRUCTURE OF THE HUMAN OVARIAN VEIN

The human ovarian vein is of particular interest as an adult vessel wh ich changes with the different phases of reproductive life. At the ult rastructural level we have characterised the endothelium, vascular smo oth muscle and autonomic innervation of the human ovarian vein. Transm ission electron micrographs were prepared from surgical specimens of t he human ovarian vein (n = 11) to demonstrate the features of the vess el wall. The pattern of innervation was investigated using an image an alysis system which was also used with high-magnification micrographs to count and measure axonal vesicle types. Possible relationships betw een ultrastructural features and age and reproductive history were inv estigated. Endothelial cells contained Weibel-Palade bodies and numero us microfilaments. There were 3 muscle coats: no elastic lamina separa ted the endothelium from an inner layer of smooth muscle; a middle smo oth muscle layer consisted of cells orientated in a circular fashion; an outer smooth muscle layer was made up of longitudinally arranged sm ooth muscle bundles with collagen and nerves penetrating throughout. T he percentage of the vessel thickness occupied by the middle circular smooth muscle layer ranged from 0 to 33 % and fell with increasing age (r = -0.67, P < 0.05). Penetration of nerves into the circular layer was observed only in 2 of 9 specimens. The observed ultrastructural fe atures are consistent with the ability of the ovarian vein to distend substantially in response to changing circulatory demands. The vascula r endothelium may have a role in the local control of haemostasis via the synthesis and storage of von Willebrand factor. Possible mechanism s of the observed age-related decrease in the relative thickness of th e middle circular smooth muscle layer are discussed.