| Abstract: | Development of contact between trophoblast and uterine epithelium during the early stages of implantation in the cow Implantation in the cow may be divided into precontact, apposition, and adhesion phases. These can be recognized grossly at the site of nidation (18 or 19 days post inseminationem) by changes in the endometrium and in the embryonic chorion, which differs from the extraembryonic chorion. Also light and electronmicroscopical examinations of the trophoblast and uterine epithelium during the course of nidation show typical phase-correlated differences. The surfaces of trophoblastic and uterine epithelia increase and unite by interdigitiation of their microvilli. The functional relationship between blastocyst and uterus at the time of contact, as determined from their structure, is discussed. |
