Proceedings: Observations on the utero-ovarian vasculature of the sheep

The anatomical basis for a possible counter current exchange mechanism in the human adnexa

A counter current mechanism for exchange of prostaglandins between veins and arteries in the ovarian pedicle has earlier been demonstrated in the sheep. The existance of a corresponding vascular arrangement in the human ovarian pedicle has been doubted predominantly on basis of functional data which do not support a role of prostaglandins for human luteolysis. However, the present study demonstrates norphological evidence for a similar vascular anatomy in the human as in the sheep. In 43 human adnexa studied, tortuous arteries in close contact with veins were consistently found. Microscopical sections revealed thinning of the vein walls at contact areas. The possible functional significance of this finding is discussed.

The extrinsic blood vessels of the ovary of the sheep

The extrinsic ovarian blood vessels were studied in 134 ewes. In view of recent evidence that uterine luteolysis may involve venoarterial transfer of prostaglandin F2alpha in the ovarian pedicle, particular attention was paid to the interrelationships between veins and arteries. The ovarian artery and utero-ovarian vein are large vessels of conventional structure and lie in close apposition. Their walls are slightly thinner on their apposing sides. The ovarian branches of the ovarian artery are very tortuous, and closely intertwined with the plexiform ovarian branches of the utero-ovarian vein. An extensive plexus of small veins surrounds the ovarian artery and its ovarian branches. Within this plexus are many thin-walled, dilated regions, interspersed with narrow, thick-walled segments. Valves are inconstantly present at sites of entry of branches of the plexus into the major veins. Small numbers of arterio-venous anastomoses are present in the distal part of the ovarian pedicle. Unless blood can flow in a veno-arterial direction through arterio-venous anastomoses or capillary beds, the structural barrier between uterine venous and ovarian arterial blood is substantial.