Question

Why clotting proteins are present in semen ? Explain.

Answer 1

Microscopic examination of liquefied semen samples is the simplest, and must be the most common, investigation of infertility. The coagulation and liquefaction of human semen is that reproductive phenomenon most accessible to the reproductive biologist Nevertheless we still lack a convincingly physiological explanation. Comparative studies1 have regarded it as a not-very-effective semen retention mechanism, comparing it with the vaginal plug of some rodents. But these animals use the plug, with its included spermatozoa, as a “cork” behind a liquid ejaculate containing the effective sperms, which is forced up into the uterus by vaginal contraction.2,3 This is very unlike the human situation but resembles that in the rabbit, where a minute jelly-blob lodges in the narrowest part of the 8-shaped vagina, enabling contraction of the anterior part to force some of the ejaculate into the higher reaches of the tract.4 Attempts to homologise human with mouse/rat ejaculates have emphasized the high sperm content of the first fraction of human “split” ejaculates, obtained by masturbation; the relevance of this to ejaculation during copulation is very dubious. Suggestions5,6 that these first sperms escape the inhospitable vaginal milieu, into a cervical reservoir, have been rendered less plausible by the discovery7 that the spermatozoa do not experience vaginal acidity, because of the immediate buffering effect of the semen. Most of the work devoted to seminal coagulation/liquefaction8,9,10 does not even attempt theories of its function in sperm presentation to the female tract.