It is generally accepted that implantation morphologically consists of the establishment of a contact between the blastocyst and the uterine tissues. During this contact and interaction process, many physiological, biochemical and ultrastructural factors are involved. The aim of this study was to describe the ultrastructure of connection complexes between mural trophoblast cells in the blastocystic ring in the rat. Implantation sites obtained from rats on day 5 of pregnancy were studied ultrastructurally. Connected complexes were observed between mural trophoblast cells in different three types: a) dense long line connection; b) desmosome-like sturctures; c) regular suture-like interdigitation resembling parallel railings. According to the ultrastructural evidence, the trohoblast cells, exhibiting different features, suggest structural changes according to their functions.

It is generally accepted that implantation morphologically consists of the establishment of a contact between the blastocyst and the uterine tissues. During this contact and interaction process, many physiological, biochemical and ultrastructural factors are involved. The aim of this study was to describe the ultrastructure of connection complexes between mural trophoblast cells in the blastocystic ring in the rat. Implantation sites obtained from rats on day 5 of pregnancy were studied ultrastructurally. Connected complexes were observed between mural trophoblast cells in different three types: a) dense long line connection; b) desmosome-like sturctures; c) regular suture-like interdigitation resembling parallel railings. According to the ultrastructural evidence, the trohoblast cells, exhibiting different features, suggest structural changes according to their functions.