Ultrastructure of the Apex of the Rabbit Graafian Follicle During the Ovulatory Process1

Abstract

The fine structure of the graafian follicle has been examined in an attempt to elucidate some of the structural changes which occur during ovulation. The protruding apexes of mature follicles were cut from the ovaries of both mated and unmated estrous rabbits. The tissue was oriented so that sections showed full-wall thickness in the region of expected rupture. Approximately 8 hr. after mating (about 2 hr. before rupture) the tissue began a progressive phase of disintegration in the general area where the stigma normally develops. Follicles estimated to be within minutes of rupture had, at most, only fragmentary remnants of the granulosa, and the fibrous outer layers of the wall had thinned to less than 1/5 their width in follicles from unmated estrous rabbits. Not only was there a separation of cells, but also the collagen fibrils of the prerupture follicles appeared appreciably sparse in comparison to precoital control follicles. The cells dissociated in a manner which supports the idea that there is. an active deterioration of the connective tissue elements in the wall of the graafian follicle as it approaches rupture.