Significance of the Epithelial Crypts at the Bovine Utero-Tubal Junction in the Pre-Ovulatory Phase of Sperm Regulation

Because Polyspermie fertilisation is a pathological condition in mammals, arising from an excess of spermatozoa at the site of initial sperm-egg contact and leading to early death of the embryo, consideration has been given to the manner whereby the utero-tubal junction may contribute to a reduction in the numbers of spermatozoa entering the Fallopian tubes. This seems especially important in cattle since the utero–tubal junction does not exhibit swollen polypoid processes that might act physically to reduce the number of spermatozoa entering the isthmus from the uterus. In tissues prepared from animals close to the time of Ovulation, large numbers of simple glands were visible in the uterine surface and throughout the region of the utero-tubal junction and its ridges extending into the isthmus. The glands appeared as crypts, slits or craters. On the basis of a figure of 500 glands situated close to the utero-tubal junction and some 2–10 spermatozoa located within each gland, these conservative estimates suggest a temporary arrest of 1–5×10³ spermatozoa, thereby contributing to the steeply diminishing sperm gradient before the site of fertilisation. There would thus appear to be a vital physical role for the simple glands and clefts that predominate in this region, functioning importantly in the pre–ovulatory interval to pave the way for normal mono– spermic fertilisation. More subtle forms of sperm regulation by glycoprotein molecules are also considered.