SIGNIFICANCE OF THE EPITHELIAL CRYPTS AT THE BOVINE UTERO-TUBAL JUNCTION IN THE PREOVULATORY PHASE OF SPERM REGULATION

Because polyspermic fertilisation is a pathological condition in mamma ls, arising from an excess of spermatozoa at the site of initial sperm -egg contact and leading to early death of the embryo, consideration h as been given to the manner whereby the utero-tubal junction may contr ibute to a reduction in the numbers of spermatozoa entering the Fallop ian tubes. This seems especially important in cattle since the utero-t ubal junction does not exhibit swollen polypoid processes that might a ct physically to reduce the number of spermatozoa entering the isthmus from the uterus. In tissues prepared from animals close to the time o f ovulation, large numbers of simple glands were visible in the uterin e surface and throughout the region of the utero-tubal junction and it s ridges extending into the isthmus. The glands appeared as crypts, sl its 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 e ach gland, these conservative estimates suggest a temporary arrest of 1-5x10(3) spermatozoa, thereby contributing to the steeply diminishing sperm gradient before the site of fertilisation. There would thus app ear to be a vital physical role for the simple glands and clefts that predominate in this region, functioning importantly in the pre-ovulato ry interval to pave the way for normal mono-spermic fertilisation. Mor e subtle forms of sperm regulation by glycoprotein molecules are also considered.