THE ANGIOARCHITECTURE OF ESTROUS, PSEUDOPREGNANT AND PREGNANT RABBIT OVARY AS SEEN BY SCANNING ELECTRON-MICROSCOPY OF VASCULAR CORROSION CASTS

Ovarian angioarchitecture was studied by scanning electron microscopy of vascular corrosion casts in estrous, pseudopregnant (stimulated wit h human chorionic gonadotropin) and pregnant rabbits. In all samples, the proper ovarian branch of the ovarian artery (ramus ovaricus) enter ed the ovarian hilus near the caudal pole of the organ and ran paralle l to the major axis of the hilus. The extraovarian venous drainage was formed by several vessels emptying into a distal large vein. The ramu s ovaricus exhibited various degrees of coiling and branched in the me dulla. The coiling of the ramus ovaricus and its ramifications were ma intained in all samples. A venous meshwork and/or flat vein branches c losely enveloped the arterial coils found in the hilus and outer medul la. At this level numerous arteriovenous contacts were demonstrated in all samples. The coiled arteries, prior to entering the ovarian corte x, supplied several small peripheral follicles which were drained by t he hilar veins. In the cortex the coiled arteries branched in numerous thin, straight or slightly undulated arterioles which supplied develo ping estrous follicles and pseudopregnant corpora lutea. The arteriole s supplying the pregnant corpora lutea were long, large and tightly sp iraled. The venous drainage followed the modifications of the arterial supply. These data demonstrate that ovarian cycle and pregnancy induc ed significant changes in the cortical vessels, which adapted their st ructure to the temporary functional needs of the recruited follicles o r corpora lutea. Hilar and medullary vessels have permanent structures that may represent morphological devices for (a) a continuous control of the blood flow (spiral arteries) and (b) a local recirculation of endocrine products (arteriovenous contacts) comparable to the ''counte rcurrent mechanism'' previously shown to operate in ovaries of other s pecies, but not yet found in rabbits.