1 Sperm maturation
Sperm maturation is defined as the development of the ability of spermatozoa to fertilize eggs as they progress through the epididymis. The definition was first applied to in vivo fertilization where spermatozoa were removed from the caput, corpus or cauda epididymidis and in-seminated into the vagina, uterus or oviduct of different species. The ability of spermatozoa to fertilize eggs, as judged by the percentage of pregnant women, litter size,percentage of fertilized eggs flushed from the oviduct or percentage of men with patent ducts after epididymo-vasostomy who subsequently fathered children, is always higher when spermatozoa are obtained from the more distal parts of the tract (Figure 1). In some early and oft-cited work [1], the number of spermatozoa insemi-nated was not always controlled for, so the greater num-ber of spermatozoa obtained from the cauda might have biased results in the direction of greater success in that epididymal region. Later studies, with both sperm num-bers and overall motility controlled for [2, 3], confirmed this maturational process; however, the nature of sperm motility changes with maturation remained a possible con-founding factor, as caput spermatozoa that display cir-cular motion are less able to penetrate the uterotubal junc-tions [4].
1 Sperm maturationSperm maturation is defined as the development of the ability of spermatozoa to fertilize eggs as they progress through the epididymis. The definition was first applied to in vivo fertilization where spermatozoa were removed from the caput, corpus or cauda epididymidis and in-seminated into the vagina, uterus or oviduct of different species. The ability of spermatozoa to fertilize eggs, as judged by the percentage of pregnant women, litter size,percentage of fertilized eggs flushed from the oviduct or percentage of men with patent ducts after epididymo-vasostomy who subsequently fathered children, is always higher when spermatozoa are obtained from the more distal parts of the tract (Figure 1). In some early and oft-cited work [1], the number of spermatozoa insemi-nated was not always controlled for, so the greater num-ber of spermatozoa obtained from the cauda might have biased results in the direction of greater success in that epididymal region. Later studies, with both sperm num-bers and overall motility controlled for [2, 3], confirmed this maturational process; however, the nature of sperm motility changes with maturation remained a possible con-founding factor, as caput spermatozoa that display cir-cular motion are less able to penetrate the uterotubal junc-tions [4].
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