Gynecology And Obstetrics Chapter 248. If periods are irregular, the time of conception and thus the duration of the pregnancy and the due date may be difficult to determine. At ovulation, the cervical mucus becomes less viscid, facilitating rapid transit of sperm from the vagina to the endometrial cavity. Sperm may live in the vagina for up to 3 days before ovulation. They can migrate to the fimbriated end of the uterine tube in 5 min under experimental conditions.
Conception occurs in the uterine tube, usually near the fimbriated end.
The tubal epithelium must function properly for the sperm and ovum to unite and for the resulting zygote to continue dividing and developing during its transit through the tube to the endometrial cavity. The zygote makes this journey in 3 to 5 days and moves to the site of implantation in 1 to 2 more days. One area of the blastocyst's wall is 3 to 4 cells thick. This area is the embryonic pole, which soon becomes recognizable as an embryo. Implantation Implantation, with the embryonic pole penetrating first, usually occurs in the front or back wall of the endometrial cavity near the fundus.