The Microvasculature of the Ovary. A Review by SEM of Vascular Corrosion Casts.

Abstract

Abstract. The vascular changes of the ovary were studied by scanning electron microscopy of vascular corrosion casts in estrous, pseudopregnant (stimulated with human chorionic gonadotropin -hCG) and pregnant rabbits. The results demonstrated that ovarian cycle and pregnancy may induce both structural and functional changes in the ovarian vessels. In fact the ovarian blood vessels adapted their structure to the temporary functional needs of the recruited follicles or corpora lutea. These changes involved both larger ovarian blood vessels (supplying the hilus and the medulla) and cortical blood vessels (supplying the luteo-follicular complexes). Hilar and medullary blood vessels also displayed morphological devices for the continuous control of the blood flow (spiral arteries) and for the local recirculation of endocrine products (artero-venous contacts). Such contacts, may likely sustain a "countercurrent mechanism" which was also shown in ovaries of other species. Scanning electron microscopy of vascular corrosion casts even demonstrated that cortical blood vessels are subjected to continuous remodeling. SEM showed different morphological types of vascular plexuses which supplied antral follicles (Types 1-2), atretic follicles (Types 3-4), peri-ovulatory follicles (Type 5), growing pseudopregnant corpora lutea (Type 6) regressing pseudopregnant corpora lutea (Type 7) and pregnant corpora lutea (Type 8). In estrous rabbit, growing to mature follicles (Types 1-2) showed a gradual enlargement and proliferation of the theca capillaries. These changes, associated with capillary hyperpermeabilization were observed in ovulatory and post-ovulatory follicles (Type 5), after hCG stimulation. The corpus luteum formation (Type 6 and 8) was accompanied by additional capillary dilation, diffuse angiogenetic sprouting and organization of conspicuous venous drainage which appeared more enhanced in pregnant (type 8) than in pseudopregnant (type 6) corpora lutea. The regression of the corpus luteum (Type 7) was characterized by the appearance of avascular areas within the gland and by regression of vascular dilatation. Finally, in estrous rabbit the atretic follicles (Types 3-4) wall showed large interruptions (avascular areas) and focal invasion of the central cavity by newly formed capillaries arranged randomly. The hCG stimulation did not affect consistently the interstitial microvasculature. It is concluded that the gradual increase of ovarian blood flow occuring during follicle growth and corpora lutea formation is provided by a functional adaptation of major ovarian vessels and by capillary functional (vasodilation) and structural (angiogenesis) support as well. Key words: Ovary, Blood vessels, Capillary, Corrosion casts, Angiogenesis, Scanning electron microscopy, Rabbit.(J. Reprod. Dev. 46: [207][208][209][210][211][212][213][214][215][216][217][218][219][220][221][222][223][224][225] 2000) ndocrine and ovulatory activities of the ovary have strict and continuous relationship with -Reviewblood vessels changes. In fact...

Changes in the Thecal Vasculature During Follicular Atresia in the Ovary of Swamp Buffalo

“…Additionally, scanning electron microscopy studies of ovarian follicle corrosion casts of various animals revealed similar observations [5,[13][14][15][16][17]. Thus, these findings support the concept that follicular atresia is accompanied by significant thecal capillary structural changes [18].…”

The ovarian and uterine arteries in the chinchilla (Chinchilla lanigera)

“…This close anatomical relationship was described previously in other species, such as guinea-pigs 9 , rats 13 , rabbits 11,18 , mice 6 , primates such as Rhesus monkeys 8 and, baboons 21 .…”

“…However, in guinea pigs, the arteria ovarica originated either from the aorta at about the level of origin of the arteria renalis, direct branches of arteria renalis, or common trunks with arteria renalis and in some cases formed anastomoses with branches of the arteria renalis 9 . In rabbits, it arose from the aorta abdominalis, immediately behind the origin of the inferior mesenteric artery 3 , whereas it left the abdominal aorta slightly caudal to the arteria renalis in mice 6 , New Zealand rabbits 11 and in rats 2,23 . Each of the ovarian arteries after emerging from the aorta abdominalis, divided into 2 branches, the caudal branches served the Fallopian tubes and uterine horns, and the cranial branch mainly supplied blood to the ovary in guinea pigs 4,8,9 , rats 4,8 , mice 6 and in New Zealand rabbits 11 .…”

Involvement of follicular basement membrane and vascular endothelium in blood–follicle barrier formation of mice revealed by ‘in vivo cryotechnique’

“…Ovarian follicles of living animals have been known to be dynamic structures that undergo a gradual increase in volume during the various phases preceding ovulation, and the follicular development is always accompanied by significant structural changes of perifollicular capillary networks (Macchiarelli 2000). The perifollicular capillary networks are initially formed when the membrana granulosa of secondary follicles has developed into a multilayered follicle cell population.…”

“…The perifollicular capillary networks are initially formed when the membrana granulosa of secondary follicles has developed into a multilayered follicle cell population. Furthermore, they also develop a single-layered to multilayered thick theca interna, as the secondary follicles grow up to larger or mature Graafian follicles (Kanzaki et al 1982, Kitai et al 1985, Kranzfelder & Maurer-Schultze 1989, Yamada et al 1994, Macchiarelli 2000, Jiang et al 2002. These morphological changes of the follicular microvasculature have shown an urgent need for increased blood supply and nutritional support systems during the follicular development and oocyte maturation.…”