Human fertilization in vivo, with special reference to progression, storage and release of competent spermatozoa.

Whilst very large numbers of spermatozoa accumulate in the cervical mucus and crypts in the hours following coitus, evidence is offered from species with comparable gonadotrophin surge-to-ovulation intervals to suggest that the cervix is not the site of the functional sperm reservoir in women. On the contrary, human spermatozoa involved in the events of fertilization may spend the greater part of the pre-ovulatory interval in the distal portion of the Fallopian tube, that is in the intra-mural segment. This would enable spermatozoa to be arrested within reach of the site of fertilization in the ampullary region of the tube, and to be activated and released close to the time of ovulation by means of a local transfer of high concentrations of ovarian follicular hormones. The clinical importance of confirming this proposed role for the intra-mural segment of the tube is stressed, as is the possibility of specific micro-environments within the lumen of the duct.