Microvascular Corrosion Casting of the Ovary in Non‐pregnant and Pregnant Does

The ovary is one of the most dynamic examples of cyclic angiogenesis. Continuous changes in its structures are accompanied by equally significant modifications in its microvasculature. Morphological changes on the caprine ovarian surface in non‐pregnant and pregnant does at different stages of pregnancy were examined using scanning electron microscopy. No significant differences were observed on the surface of ovaries from non‐pregnant or pregnant does; nor between stages of pregnancy, and/or between the right and left ovaries. In all ovaries, the proper ovarian branch of the ovarian artery ran toward the hilus of the ovary, where it penetrated the ovary. Subdivisions of the proper ovarian branch of the ovarian artery coiled around the proper ovarian tributary of the ovarian vein from the level of their origin to within the substance of the ovary. The arterial and venous branches of large vessels penetrating the ovary showed distinct microvascular patterns characteristic of the follicles and corpora lutea. In the early preantral follicle, these appeared as a spherical, basket‐like network of capillaries. At later stages, follicles possessed a highly complex wreath of capillaries, which tend to be arranged into layers. Late well‐developed antral follicles acquired a well‐defined multilayered basketlike network, the inner wall of which was characterized by development of capillary sinusoids. Capillary sprouts and evidence of intussusceptive capillary growth due to enhanced angiogenesis were seen in inner wall of the late developed follicles. The outer wall was formed from larger size vessels. Ovulatory follicles were characterized by the presence of an avascular apical area at the location of the stigma. Leakage of casting medium was observed around the border of the stigma due to increased vascular permeability in this region. Early formation of the corpus luteum was characterized by inward growth of vessels from the apical part of the ovulating follicle, followed by extensive new formation of capillaries, which filled up the corpus luteum and closed the apical area. Corpora lutea could be recognized by their complex vasculature. The vascular bed of the corpus luteum consisted of a dense, conglomerated capillary plexus, and large vessels distributed on its outer surface. Large flat veins could be observed on the outer surface of the corpus luteum. Coiling of vessels might represent a local channel required for product transport needed to allow the transfer of substances produced in the ovary from the ovarian vein to the ovarian artery. In other words, physiological processes occurring in the ovary can be controlled by the ovary itself; this should be investigated further.