human sperm is stored in the epididymis in the body.
human sperm is stored in the epididymis in the body.
where is human sperm stored in the body?
in the epididymis
an alternative proposal is that testicular descent was preceded, and possibly influenced, by migration of the sperm storage region of the epididymis to a cooler extra-abdominal location. the evolutionary adaptive advantage of testicular descent into an extra-abdominal position may be related more to the enhanced sperm storage capacity of the epididymis at lower extra-abdominal temperatures than to the testis itself. greater sperm storage capacity in the epididymis has been associated with enhanced fertility. in this context, the proportion (26% of total) of mature sperm stored intra-abdominally in the monotreme epididymis is considerably less than the proportion of mature sperm stored in the epididymis of many eutherian mammals (50-75% of total) with descended testes.
evolution of descended testes in mammals
sialyl-lewis allows a sperm cell to recognize and fertilize an egg cell. for fertilization to occur, human sperm must bind to the zona pellucida (zp), the translucent matrix covering the human egg composed of four glycoproteins zp1, 2, 3, and 4, and transit through the matrix in order to fuse with the oocyte. human zp is coated with highly dense n- and o-glycans that are terminated with the sialyl-lewis sequence. the hemizona assay, which assesses sperm-zp binding by counting the number of sperm bound to hemispheres of bisected nonliving human eggs "in vitro", revealed that as little as 0.5 mm sialyl-lewis inhibits sperm-zp binding by 63%. furthermore, adding purified and solubilized zp3 or zp4 from the human oocyte dose-dependently inhibits sperm-zp binding in the hemizona assay. such evidence suggest that the early steps of human sperm-egg binding may be mediated by lectins for sialyl-lewis present on human sperm.
sialyl-lewis x