Spermatogenesis, Spermiation and the Human Sperm

In men, the reproductive system has the central purpose of producing spermatozoa capable of fertilising the oocyte within the female reproductive tract. In addition, the male reproductive system must also secrete a series of hormones that stimulate the continuous production of spermatozoa which, once initiated at puberty, will continue throughout a man’s life. Finally, the anatomy of the male reproductive system must provide an environment suitable to ensuring the processes of spermatogenesis and spermiation can occur in a continuous and highly coordinated manner. Spermatogenesis involves the dramatic remodelling of relatively undifferentiated diploid, spermatogonial stem cells into highly specialised haploid spermatozoa. Within the seminiferous tubules of the testes, the spermatogonium undergo mitosis, maintaining the stem cell pool while also generating primary spermatocytes. Through subsequent rounds of meiosis and cell remodelling, spermatids are generated, each with unique genetic identity. Subsequently, through the process of spermiogenesis, the spermatids differentiate further into spermatozoa with fully condensed chromatin. Finally, under spermiation, the mature spermatids are released into the lumen of the seminiferous tubule prior to their final maturation within the epididymis. This highly co-ordinated process is maintained and supported by a series of extrinsic and intrinsic factors and supporting cells, all critical in supporting male reproduction and fertility.