Scanning electron microscopic morphometry of a discriminated population of elongated human spermatozoa.

A scanning electron microscopic study was carried out on long-headed sperm from normal human semen with the purpose of establishing morphometrical standards for this atypical variety which is difficult to differentiate from the normal type in the spermocytogram. Subjective discrimination between the two populations (with elongated and normal heads) was confirmed by multidimensional analyses. They also made statistical identification of thin-headed spermatozoa (an intermediate form between the two preceding types) possible. Moreover, through the analyses an elongation index for distinguishing the elongated type from light microscopic observations was able to be calculated. Statistical data showed that the acrosome accounted for 30% of the elongated head, the postacrosomal cap and the posterior nuclear space--both bounded by furrows--occupied 9% and 6% respectively, whereas the posterior part of the head, covered by a voluminous cytoplasmic sheath, took up 56%. This lengthening of the head was accompanied by an elongation of the middle piece which thus became the second most important discriminating factor between the two populations.